Is Intermittent Fasting Really Worth It?


After all, 16 hours is a long time to go without eating. Here’s everything you need to know about the popular weight-loss regimen—including whether it actually works.

Chris Pratt! Hugh Jackman! Halle Berry! Kourtney Kardashian! What these celebrities have in common, other than a gratuitous exclamation point after their names, is a professed fondness for intermittent fasting, the diet craze turning the fitness world on its sweaty, well-toned head. For help determining whether you, too, should incorporate this into your 2019 resolution-related plans, we asked a few experts to explain what it is, why people love it, and whether it’s really worth the pain of forgoing on-demand snacks for the rest of the winter.

illustration of a man eating while using a clock as a table


What is intermittent fasting, exactly?

Intermittent fasting, unlike many other diets, is famously flexible in that you choose the days and hours during which you think it’s best to fast. The two most common methods are the 16:8 strategy—where you eat whatever you want (within reason) for eight hours a day and then fast for the other 16—and the 5:2 method, where you eat normally five days a week and then keep your food intake to roughly 500-600 calories for the other two days. It’s kind of a simplified-calories math problem that’s supposed to prevent the yo-yo effect of weight loss and weight gain.

“There are different ways to do this diet, but the bottom line is that no matter which you choose, you’re taking in less energy, and because of that, you’re going to start using your own body stores for energy,” says Lisa Sasson, a clinical professor of nutrition at NYU. “If you don’t, you’re not going to lose weight.”

Why might I want to try it?

A recent study completed by the German Cancer Research Center concluded that intermittent fasting indeed “helps lose weight and promotes health,” and noted that the regimen proved especially adept at getting rid of fat in the liver. A USC study also found that the diet reduced participants’ risk of cancer, diabetes, heart disease, and other age-related diseases. While researchers involved cautioned that more testing is necessary, the results are at least encouraging.

Most people who swear by intermittent fasting will tell you it helps not only with losing weight but also with reducing “belly fat.” This is not a conclusion with scientific backing, but it is the sort of thing to which every six-pack enthusiast aspires.


Why might I not want to try it?

“There’s really no conclusive evidence that there’s any benefit,” Sasson says. The German Cancer Research Center study qualified its findings by noting that the positive results weren’t noticeably better than those experienced by subjects who adopted a conventional calorie-reduction diet. In other words, it works, but not notably better than the alternative. (Sasson also offered a helpful list of individuals who should not give intermittent fasting a try: pregnant women and anyone with diabetes, cancer, or an eating disorder.)

The best long-term diets, no matter what their rules entail, are the ones that are least difficult to maintain—and again, in this regard, intermittent fasting isn’t inherently superior to anything else. “Are you making changes in your behavior? Have you learned positive habits so that when you go back to not fasting, you’re going to be a healthier eater?” Sasson asks. “I know people who fast because they think, Okay, I’m going to be really bad and overdrink or overeat, and then two days a week I’m going to have a clean life, and that’s just not how it works.”

Also, for many people, a full 16 hours of fasting just isn’t realistic, says Cynthia Sass, a New York City– and L.A.-based performance nutritionist. She recommends 12 hours of overnight fasting at most and believes the 16-hour gap is especially tough on those who exercise early in the morning or late at night. “If fasting makes you feel miserable and results in intense cravings and rebound overeating, it’s not the right path for you,” she says.

So—should I try it?

As long as you’re aware that it isn’t nutritional magic, Sasson isn’t against intermittent fasting altogether. “I’ve worked with patients who need positive reinforcement to see that their weight went down to feel better, and they feel in control for the first time,” she says. “That self-efficacy, that feeling that they could do it—for some, that might be important.”

Of the two most popular methods, Sasson leans toward the 5:2 schedule as slightly more manageable, since you’re only reducing your intake twice a week. But again, that’s contingent on you being a responsible dieter on your days of lowered caloric intake, which requires an immense amount of discipline—especially when it comes to remembering to drink water. “You can go a long time without food, but only a few days without adequate hydration,” she warns.

If these extended periods without delicious food sound too painful to handle, rest assured: The best available evidence indicates that a regular ol’ diet is at least as safe and healthy and efficacious as intermittent fasting. Besides, sooner or later, a shiny new fad is bound to come along for the A-listers to fawn over, she says: “There’s going to be a new darling of the month before you know it.”

Intermittent Fasting No Better Than Other Calorie Restriction Diets


Scientists have concluded that intermittent fasting, also referred to as the 5:2 diet or the 16:8 diet, does help with weight loss, but it’s no better than conventional calorie restriction diets for losing weight. An example of an intermittent fasting diet is feasting for 8 hours and then fasting for 16 hours. Some intermittent fasting studies have shown positive results for metabolic health.

For this current study, 150 obese and overweight individuals were examined over a 1 year period. They were randomly assigned to 3 groups at the beginning of the study: One group followed a conventional diet which reduced daily calorie intake by 20%. The 2nd group followed a 5:2 dietary plan which restricted calorie intake by 20%. A control group did not follow any specific diet plan. All participants were advised to eat a healthy, well-balanced diet. After the actual dieting stage, the health status and weight of the participants were documented for an additional 38 weeks.

Health status improvements were found to be the same with both methods of dieting. Participants of both groups lost body weight, and belly fat as well as extra fat in the liver was reduced. Body weight distribution changes were determined exactly making use of special MRT imaging. A body weight reduction of only 5%, no matter which dietary method was used, resulted in a 20% loss of dangerous visceral fat and more than a third of fat in the liver. The investigators also did not find any difference in any other metabolic values between the two dieting methods.

Although the study shows an intermittent fasting diet method to be no superior than conventional calorie restriction diets, it also reveals that this method isn’t any less beneficial. It might also be easier for some people to be disciplined for just 2 days instead of restricting calories every day. The results show that it’s not primarily the dietary method which matters but that it’s more important to follow through with the chosen method, and a balanced diet should be followed in order to maintain the new body weight. Health will benefit from weight loss either way, so long as it’s achieved on the basis of a well-balanced diet.[1]

Intermittent Fasting

What the Science Says About Intermittent Fasting


Story at-a-glance

  • It’s long been known that calorie restriction can increase the lifespan of certain animals. More recent research suggests that intermittent fasting can provide the same health benefits as constant calorie restriction, which may be helpful for those who cannot successfully reduce their everyday calorie intake
  • “Undernutrition without malnutrition” is the only experimental approach that consistently improves survival in animals with cancer, and extends overall lifespan by about 30 percent
  • Both intermittent fasting and continuous calorie restriction have been shown to produce weight loss and improve metabolic disease risk markers. However, intermittent fasting tends to be slightly more effective for reducing insulin resistance
  • Besides turning you into an efficient fat burner, intermittent fasting can also boost your level of human growth hormone (aka the “fitness hormone”) production by as much as 1,200 percent for women and 2,000 percent for men
  • Intermittent fasting can improve brain function by boosting production of the protein BDNF, which activates brain stem cells to convert into new neurons and triggers other chemicals that promote neural health. This protein also protects your brain cells from changes associated with Alzheimer’s and Parkinson’s disease, and helps protect your neuro-muscular system from degradation

By Dr. Mercola

Is it a good idea to “starve” yourself just a little bit each day, or a couple of days a week? Mounting evidence indicates that yes, intermittent fasting (IF) could have a very beneficial impact on your health and longevity. I believe it’s one of the most powerful interventions out there if you’re struggling with your weight and related health issues. One of the primary reasons for this is because it helps shift your body from burning sugar/carbs to burning fat as its primary fuel.

As discussed in the featured article,1 intermittent fasting is not about binge eating followed by starvation, or any other extreme form of dieting. Rather what we’re talking about here involves timing your meals to allow for regular periods of fasting. I prefer daily intermittent fasting, but you could also fast a couple of days a week if you prefer, or every other day. There are many different variations.

To be effective, in the case of daily intermittent fasting, the length of your fast must be at least 16 hours. This means eating only between the hours of 11am until 7pm, as an example. Essentially, this equates to simply skipping breakfast, and making lunch your first meal of the day instead. You can restrict it even further — down to six, four, or even two hours if you want, but you can still reap many of these rewards by limiting your eating to an eight-hour window each day.

This is because it takes about six to eight hours for your body to metabolize your glycogen stores; after that you start to shift to burning fat. However, if you are replenishing your glycogen by eating every eight hours (or sooner), you make it far more difficult for your body to use your fat stores as fuel.

Intermittent Fasting — More a Lifestyle Than a Diet

I have been experimenting with different types of scheduled eating for the past two years and currently restrict my eating to a 6- to 7-hour window each day. While you’re not required to restrict the amount of food you eat when on this type of daily scheduled eating plan, I would caution against versions of intermittent fasting that gives you free reign to eat all the junk food you want when not fasting, as this seems awfully counterproductive.

Also, according to research published in 2010,2 intermittent fasting with compensatory overeating did not improve survival rates nor delay prostate tumor growth in mice. Essentially, by gorging on non-fasting days, the health benefits of fasting can easily be lost. If so, then what’s the point?

I view intermittent fasting as a lifestyle, not a diet, and that includes making healthy food choices whenever you do eat. Also, proper nutrition becomes even more important when fasting, so you really want to address your food choices before you try fasting.

This includes minimizing carbs and replacing them with healthful fats, like coconut oil, olive oil, olives, butter, eggs, avocados, and nuts. It typically takes several weeks to shift to fat burning mode, but once you do, your cravings for unhealthy foods and carbs will automatically disappear. This is because you’re now actually able to burn your stored fat and don’t have to rely on new fast-burning carbs for fuel. Unfortunately, despite mounting evidence, many health practitioners are still reluctant to prescribe fasting to their patients. According to Brad Pilon, author of Eat Stop Eat:3

“Health care practitioners across the board are so afraid to recommend eating less because of the stigma involved in that recommendation, but we are more than happy to recommend that someone start going to the gym. If all I said was you need to get to the gym and start eating healthier, no one would have a problem with it. When the message is not only should you eat less, you could probably go without eating for 24 hours once or twice a week, suddenly it’s heresy.”

The Health Benefits of Intermittent Fasting

Aside from removing your cravings for sugar and snack foods and turning you into an efficient fat-burning machine, thereby making it far easier to maintain a healthy body weight, modern science has confirmed there are many other good reasons to fast intermittently. For example, research presented at the 2011 annual scientific sessions of the American College of Cardiology in New Orleans4 showed that fasting triggered a 1,300 percent rise of human growth hormone (HGH) in women, and an astounding 2,000 percent in men.

HGH, human growth hormone, commonly referred to as “the fitness hormone,” plays an important role in maintaining health, fitness and longevity, including promotion of muscle growth, and boosting fat loss by revving up your metabolism. The fact that it helps build muscle while simultaneously promoting fat loss explains why HGH helps you lose weight without sacrificing muscle mass, and why even athletes can benefit from the practice (as long as they don’t overtrain and are careful about their nutrition). The only other thing that can compete in terms of dramatically boosting HGH levels is high-intensity interval training. Other health benefits of intermittent fasting include:

  • Normalizing your insulin and leptin sensitivity, which is key for optimal health
  • Improving biomarkers of disease
  • Normalizing ghrelin levels, also known as “the hunger hormone”
  • Reducing inflammation and lessening free radical damage
  • Lowering triglyceride levels
  • Preserving memory functioning and learning

Intermittent Fasting Is as Good or Better Than Continuous Calorie Restriction

According to Dr. Stephen Freedland, associate professor of urology and pathology at the Duke University Medical Center, “undernutrition without malnutrition” is the only experimental approach that consistently improves survival in animals with cancer, as well as extends lifespan overall by as much as 30 percent.5 Interestingly enough, intermittent fasting appears to provide nearly identical health benefits without being as difficult to implement and maintain. It’s easier for most people to simply restrict their eating to a narrow window of time each day, opposed to dramatically decreasing their overall daily calorie intake.

Mark Mattson, senior investigator for the National Institute on Aging, which is part of the US National Institutes of Health (NIH), has researched the health benefits of intermittent fasting, as well as the benefits of calorie restriction. According to Mattson,6 there are several theories to explain why fasting works:

“The one that we’ve studied a lot, and designed experiments to test, is the hypothesis that during the fasting period, cells are under a mild stress, and they respond to the stress adaptively by enhancing their ability to cope with stress and, maybe, to resist disease… There is considerable similarity between how cells respond to the stress of exercise and how cells respond to intermittent fasting.”

In one of his studies,7 overweight adults with moderate asthma lost eight percent of their body weight by cutting their calorie intake by 80 percent on alternate days for eight weeks. Markers of oxidative stress and inflammation also decreased, and asthma-related symptoms improved, along with several quality-of-life indicators.

More recently, Mattson and colleagues compared the effectiveness of intermittent fasting against continuous calorie restriction for weight loss, insulin sensitivity and other metabolic disease risk markers. The study, published in the International Journal of Obesity in 2011,8 found that intermittent fasting was as effective as continuous calorie restriction for improving all of these issues, and slightly better for reducing insulin resistance. According to the authors:

“Both groups experienced comparable reductions in leptin, free androgen index, high-sensitivity C-reactive protein, total and LDL cholesterol, triglycerides, blood pressure and increases in sex hormone binding globulin, IGF binding proteins 1 and 2. Reductions in fasting insulin and insulin resistance were modest in both groups, but greater with IER [intermittent fasting] than with CER [continuous energy restriction].”

How Intermittent Fasting Benefits Your Brain

Your brain can also benefit from intermittent fasting. As reported in the featured article:

“Mattson has also researched the protective benefits of fasting to neurons. If you don’t eat for 10–16 hours, your body will go to its fat stores for energy, and fatty acids called ketones will be released into the bloodstream. This has been shown to protect memory and learning functionality, says Mattson, as well as slow disease processes in the brain.”

Besides releasing ketones as a byproduct of burning fat, intermittent fasting also affects brain function by boosting production of a protein called brain-derived neurotrophic factor (BDNF). Mattson’s research suggests that fasting every other day (restricting your meal on fasting days to about 600 calories), tends to boost BDNF by anywhere from 50 to 400 percent,9 depending on the brain region. BDNF activates brain stem cells to convert into new neurons, and triggers numerous other chemicals that promote neural health. This protein also protects your brain cells from changes associated with Alzheimer’s and Parkinson’s disease.

BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation. (The neuromotor is the most critical element in your muscle. Without the neuromotor, your muscle is like an engine without ignition. Neuro-motor degradation is part of the process that explains age-related muscle atrophy.) So BDNF is actively involved in both your muscles and your brain, and this cross-connection, if you will, appears to be a major part of the explanation for why a physical workout can have such a beneficial impact on your brain tissue — and why the combination of intermittent fasting with high intensity exercise appears to be a particularly potent combination.

Give Intermittent Fasting a Try

If you’re ready to give intermittent fasting a try, consider skipping breakfast, make sure you stop eating and drinking anything but water three hours before you go to sleep, and restrict your eating to an 8-hour (or less) time frame every day. In the 6-8 hours that you do eat, have healthy protein, minimize your carbs like pasta, bread, and potatoes and exchange them for healthful fats like butter, eggs, avocado, coconut oil, olive oil and nuts — essentially the very fats the media and “experts” tell you to avoid.

This will help shift you from carb burning to fat burning mode. Once your body has made this shift, it is nothing short of magical as your cravings for sweets, and food in general, rapidly normalizes and your desire for sweets and junk food radically decreases if not disappears entirely.

Remember it takes a few weeks, and you have to do it gradually, but once you succeed and switch to fat burning mode, you’ll be easily able to fast for 18 hours and not feel hungry. The “hunger” most people feel is actually cravings for sugar, and these will disappear, as if by magic, once you successfully shift over to burning fat instead.

Another phenomenal side effect/benefit that occurs is that you will radically improve the beneficial bacteria in your gut. Supporting healthy gut bacteria, which actually outnumber your cells 10 to one, is one of the most important things you can do to improve your immune system so you won’t get sick, or get coughs, colds and flus. You will sleep better, have more energy, have increased mental clarity and concentrate better. Essentially every aspect of your health will improve as your gut flora becomes balanced.

Based on my own phenomenal experience with intermittent fasting, I believe it’s one of the most powerful ways to shift your body into fat burning mode and improve a wide variety of biomarkers for disease. The effects can be further magnified by exercising while in a fasted state. For more information on that, please see my previous article High-Intensity Interval Training and Intermittent Fasting – A Winning Combo.

Clearly, it’s another powerful tool in your box to help you and your family take control of your health, and an excellent way to take your fitness to the next level.

Is fasting the fountain of youth?


For the past year and a half, Keith Taylor and his wife have adopted a lifestyle that includes fasting on a regular basis. “For six days per week we don’t eat until around 5 pm, but eat as much as we want and whatever we want from 5 pm until we go to bed. It is not a diet in the classic sense — we do not restrict WHAT we eat or HOW MUCH we eat, but rather just WHEN we eat,” Taylor said in an email.

 

Since the Taylors have been intermittently fasting, often called just IF, they’ve maintained a healthy body weight, been more alert and energetic, experienced less stress, and are less prone to getting sick. While Taylor admits that whether or not he will live longer as a result of his eating pattern is a “good question,” but he feels optimistic.
“I already feel as though I am younger,” said Taylor. “And if I am showing objective signs of being younger — more vigor and positivity — then I think it is logical to assume that I have already lengthened my lifespan by moving to IF.”
empty plate

Research on fasting

Research involving animals has revealed that intermittent fasting can reduce the risk of obesity and its related diseases, including non-alcoholic fatty liver disease, diabetes and cancer. According to Mark Mattson, chief of the Laboratory of Neurosciences at the National Institute on Aging, research from the 1980s revealed that the lifespan of rats increases substantially when they fast every other day, compared to rats who have food available at all times.
A much more recent study, published this month, found that mice who fasted, whether because they were fed all of their calories only once per day or because their calories were restricted, which naturally caused them to eat all of their limited food at once — were healthier and lived longer compared to mice who had constant access to food.
Trying to tease out whether fasting is simply a form of calorie restriction is very complicated, according to experts. But “in the absence of calorie restriction, and independent of diet composition, fasting mice do better than non-fasting,” explained Rafael deCabo, a scientist at the National Institute on Aging and the study’s lead author.
But do the health benefits of fasting, including the possibility of living a longer life, apply to humans?
So far, research has revealed promising results. One study published last year divided 100 people, all free of disease, into two groups. For three months, participants either ate whatever they wanted, or consumed between 800 and 1,100 calories for only five days out of the month — a pattern researchers refer to as a “fasting mimicking diet” or “FMD.” At the end of the study period, participants on the FMD who were at risk for disease saw their fasting glucose, an indicator of diabetes risk, return to normal. Markers for heart disease, along with high levels of cholesterol and triglycerides, decreased, as did levels of the 1GF1 marker of various cancers. Additionally, participants lost abdominal fat, while preserving lean muscle mass and metabolism, which is often sacrificed on a lower calorie diet.
A human trial on longevity is almost impossible to design, and would cost “a hundred million dollars or more,” according to Valter Longo, who co-authored the clinical study. “But if you look at the data from our trial … it would be hard to see how they would not live longer.”
“You think of diseases when you think of lifespan — like cardiovascular disease, cancer and diabetes — as major causes of death,” said Mattson. And if you have improvements in risk factors for disease, it does, “on average” promote lifespan, explained Mattson.
Longo, who also runs the Longevity Institute at the University of Southern California’s Leonard Davis School of Gerontology, adds that periodic fasting provides a “potential alternative to taking lots of drugs.”
And no major diet changes are necessary. “You can do this for five days, and then go back to what you would do normally,” added Longo.
The research behind the popular 5:2 diet — a type of intermittent fasting where people eat whatever they want for five days per week, then limit their diet to 500 calories for two consecutive days, has also revealed health benefits.
“We published two studies with Dr. Michelle Harvie at the University of Manchester; each included 100 overweight women, and the design of both studies was the same,” said Mattson. “We divided them into two groups; one group got the 5:2 diet; the other group had three meals per day but we reduced the amount of calories by 20% to 25% below what they normally eat — so that the weekly calorie intake of both groups would be the same.”
Both groups lost the same amount of body weight over a 6-month period, but that was where the similarities ended. “We saw superior beneficial effects of 5:2 diet on glucose regulation (a risk factor for diabetes) and loss of belly fat (a risk factor for cardiovascular disease) compared to the women eating regular meals but restricting calories,” said Mattson.
A form of fasting known as time-restricted feeding, where meals are consumed within a limited number of hours each day — like the Taylors are doing — has revealed beneficial effects on weight and health in animals, but a review article published in 2015 concluded that the data from human studies on this type of eating pattern is limited.
A study from June revealed health benefits of a time-restricted eating pattern in the absence of weight loss among pre-diabetic men; however, the study only included eight participants. The study’s researchers admit the “results need to be replicated in a larger trial that also includes women.”
Clinical trials are currently underway of IF in patients with various diseases such as multiple sclerosis or cancer to determine if fasting can halt progression. “If you hit cancer cells with chemo or radiation, when the individual is in a fasting state, the cells may be more vulnerable to being killed because they use glucose and cannot use ketones [the source of fuel during fasting],” explained Mattson. Researchers are also currently studying how fasting may impact cognitive performance and the risk of Alzheimer’s disease in overweight women.

How fasting may help you live longer

According to experts, a critical aspect of fasting — which is different from simply restricting calories — is that the body undergoes a metabolic switch from using glucose to using ketones as fuel, a result of the depletion of liver energy stores and the mobilization of fat. (This switch also occurs during extended periods of exercise.)
“If ketones are not elevated, you don’t see the beneficial effects,” said Mattson. What’s more, these metabolic changes that occur during repeated “cycling” from fasting to eating may help to optimize brain function and bolster its resistance to stress and disease, both of which have positive implications for aging.
According to Longo, the presence of ketones in the blood signifies that on the cellular level, the body is “regenerating” itself, which protects against aging and disease.
“We’ve published many papers, and the main thing we talk about is multisystem regeneration,” said Longo. For example, fasting seems to lower the level of damaged white blood cells — but when you re-feed, stem cells are turned on, and you rebuild and regenerate new, healthy cells, explained Longo. “You get rid of the junk during starvation — and once you have food, you can rebuild.”
“The damaged cells are replaced with new cells, working cells — and now the system starts working properly,” said Longo. This ultimately impacts disease risk, as risk factors for disease decrease when tissues are healthy and functional, explained Longo.

Fasting factors to consider

One point to consider is that the research on fasting has focused mostly on overweight individuals or those with risk factors for disease. If you are aging at a healthy body weight and are free of disease, and you eat a healthy diet and regularly exercise, periodic fasting may not necessarily offer an added benefit in terms of lengthening your life. “If you are already doing everything right … then I wouldn’t necessarily recommend switching to IF,” said Mattson.
Fasting is also not appropriate for pregnant women and those with medical conditions such as diabetes or eating disorders.
According to Samantha Heller, a registered dietitian and senior clinical nutritionist at NYU Langone Health in New York, the jury is still out on how healthy, sustainable and realistic the approach is. Though some people may feel better as a result of fasting, “eating very low calories, or none, on alternate days feels punitive to many and may exacerbate an already difficult and complex relationship someone has with food,” said Heller.
Experts say if you are considering a fasting diet, it’s crucial to have a doctor’s approval, and to be medically monitored. It’s also wise to meet regularly with a registered dietitian who can monitor your eating patterns, because it’s easy to overdo it on non-fasting days, especially when you are not in a controlled setting like the study participants were in, explained Angela Lemond, a registered dietitian and national spokesperson for the Academy of Nutrition and Dietetics. “The benefits [of fasting] are counteracted if you are going to make up for the calories the next day,” said Lemond.
Another consideration is to think about what type of pattern will make sense for your lifestyle. Mattson engages in time-restricted feeding, a practice he has adopted for more than 30 years, where he consumes all of his 2,000 calories between 3 p.m. and 8 p.m.
His regimen, which includes lots of fruits, vegetables, nuts, beans and oatmeal, along with fish and chicken cooked by his wife, allows him to get to work at his laboratory by 7 a.m., and affords him time for an early afternoon run. (Note: He claims that once you adapt to skipping breakfast, your circadian rhythms adjust appropriately and you don’t experience negative side effects, including an increased risk for weight gain.)

 

Finally, it’s important to remember that even though your health might improve from fasting, other factors including genetics and the environment can also determine how long you will ultimately live.
And being healthy isn’t always associated with a longer life. “We always try to link survival with health, but there is a clear separation with health and survival … and we’ve seen that in many cases,” said deCabo. “The preclinical data based on our studies is that the answer is yes — you can benefit [from fasting] in terms of health and lifespan — but we do not know what [the outcome] would be in humans.”
“There are so many unknown factors, including life experiences and how they influence your health,” echoed Mattson. “I think I’ve increased my chances [of living longer], but there’s no guarantee.”

Intermittent Fasting: The Risks and Rewards


Slim down. Cure your cancer. Reverse your multiple sclerosis. Prevent heart attacks. Live longer. Reports that intermittent fasting could help with the biggest health concerns facing people in developed countries have inspired millions to take it up.

In one survey, 10% of Americans aged 16-34 said they fast intermittently, making it the most popular style of diet for that age group.[1]

“It has, to a certain extent, become one of the fad diets of the time right now,” says Benjamin Horne, PhD, MPH, director of cardiovascular and genetic epidemiology at Intermountain Healthcare in Salt Lake City, Utah, who is researching the health effects.

As with so many health fads, though, the evidence for intermittent fasting—in which participants drastically restrict energy intake for some part of a day, a week, or a month—lags behind the enthusiasm of the participants. Careful clinical trials have so far shown that intermittent fasting can help people lose weight, but not necessarily better than more conventional diets.

More dramatic findings—including effects on cancer and cardiovascular and neurologic health—come mostly from on studies in animals, with only a few tantalizing results in humans so far reported.

And although careful fasting regimens appear to be safe for most people, there may be some risks. “A lot of people are going to get hurt,” predicts Valter Longo, PhD, director of the Longevity Institute at the University of Southern California.

The Data on Calorie Restriction

The notion that some form of fasting might have health benefits is nothing new, but it has gained currency in recent decades because of research showing that calorie restriction can dramatically extend the lifespans of many life forms. If you put baker’s yeast in plain water, for example, it will live several times longer than if you put in on a gel with sugar.

Experiments with calorie restriction have lengthened the lives of bacteria, worms, mice, rats, and monkeys.[2] Research suggests that fasting activates genes responsible for protecting DNA from oxidation, and reducing production of toxic molecules.[2]

Studies in humans are more difficult, but a 2-year trial suggested that reducing calorie consumption by 12% might improve lifespan and overall health because it improved such biomarkers as body mass index, lipid profile, glucose tolerance, insulin action, and inflammation that are indicative of reduced risk for chronic disease.[3]

However, the trial also illustrated the difficulty of simple calorie restriction. Participants failed to achieve the 25% calorie reduction that the investigators set as their goal. And even that 25% is short of the 30%-50% that has achieved the most dramatic effects in animals.[4]

More severe calorie restriction may cause health problems as well, such as reduced lean body mass and bone mineral density,[4] and an increased risk for anemia and gallstones.[5]

In addition, Longo warns, there is the possibility that metabolism will slow down in people who restrict their calories for a long period. “It may take years to recover that metabolism,” he says. If they then revert to their previous diets, calorie restrictors could put on more weight than they lost. And staying on a diet that reduces calorie intake by as much as 40% is challenging for anyone.

Consequently, researchers, including Longo and Horne, have been looking for ways to reap the benefits of calorie restriction without the problems. That led them to intermittent fasting. “People were tinkering around with regimens of calorie restriction and found that in animals, there was more benefit if it’s done over a longer time, but only periodically,” Horne says. Also, “with calorie restriction, you have this constant gnawing hunger. With intermittent fasting, you don’t have that. So potentially it’s more tolerable.”

Researchers are experimenting with a range of protocols. Longo is looking at severe calorie restriction 5 days per month. Horne is studying a water-only fast day per week. Krista Varady, PhD, an associate professor of nutrition at the University of Illinois in Chicago, has done a trial of a regimen of alternating fast days and feast days.

Others still have advocated a restriction by hours of each day: for example, 8 hours of eating and 16 hours of fasting. Despite concerns that participants would gorge themselves on feast days, the studies generally show participants losing weight on intermittent fasting, and many show improvements in biomarkers for disease risks.

In one of the more careful randomized controlled trials, Wei and colleagues[6] randomly divided 100 people into two groups. Forty-eight consumed a “fasting-mimicking diet” that was low in calories, sugars and protein but high in unsaturated fats for 5 days a month. The diet provided about 1100 kcal for day 1 and 700 kcal for days 2-5. The dieters ate whatever they wanted for the rest of the month. The other 52 participants ate whatever they wanted throughout the month as a control group.

Although there were no adverse events more serious than weakness, fatigue, and headache, after 3 months, 13 people withdrew from the fasting-mimicking group, compared with five from the control group. The fasting mimickers lost an average of 2.6 kg (in a combination of lean and fat body mass), whereas the people in the control group maintained their weights. The fasting mimickers also had a decrease in insulin-like growth factor 1 concentrations (a marker of cancer risk) and systolic and diastolic blood pressure. But fasting glucose, triglycerides, low-density lipoprotein cholesterol, and C-reactive protein (a marker of inflammation) did not differ between the groups.[6]

After 3 months, the control group joined the other participants on the intermittent diet, and a total of 71 participants completed three month-long cycles of the regimen. Those whose biomarkers put them at highest risk for cardiovascular disease or metabolic syndrome achieved the most significant improvements in these biomarkers.[6]

Such findings have pointed to a way that physicians can now prescribe intermittent fasting, says Longo. “We can recommend it for predisease conditions,” he said. “It’s fair for doctors to say, ‘Let’s do a couple of cycles. Let’s see how you respond. If you don’t respond well, we’ll think about drugs.'”

Treating Disease Through Diet

Longo has equity interest in L-Nutra, a Los Angeles company marketing the diet as ProLon, but says he donates the income to charity. He is working on research to explore whether the diet could be used to treat active diseases. For example, some studies suggest that healthy cells become more resistant to chemotherapy during intermittent fasting, whereas cancer cells do not.

In a pilot study, he and his colleagues got promising results in a study of 60 patients with relapsing-remitting multiple sclerosis. They assigned 20 each to a 6-month ketogenic diet; a combined 7 days of fasting-mimicking diet and 6-month Mediterranean diet; and a control diet.[7]

Both the ketogenic and the fasting/Mediterranean groups reported improvements on health-related quality-of-life scales. The finding supported the results in mice with experimental autoimmune encephalomyelitis; fasting mimicking suppressed their autoimmunity and caused remyelination.[8] Experiments are under way in Alzheimer disease as well.[9]

On the other hand, some people with advanced chronic diseases may not be able to tolerate fasting, Horne says. People with diabetes may get benefits, but fasting is contraindicated with certain diabetes medications, he warns.

And researchers are far from figuring out whether one intermittent fasting regimen works better than another, or even showing that fasting-mimicking works better than calorie restriction. In what they believe to be the only trial that pitted intermittent fasting against conventional calorie restriction, Varady and her colleagues recruited 100 obese, metabolically healthy adults (86 women and 14 men).[10]

They randomly assigned 34 participants to alternate-day fasting (25% of energy needs on fast days, 125% of energy needs on alternating feast days). They assigned another 35 to conventional calorie restriction (75% of their energy needs every day). The remaining 31 were instructed to maintain their weight and not to change their eating or physical activity habits.[9]

Contrary to the researchers’ expectations, more people (38%) dropped out of the study from the alternate-day fasting group than from the daily calorie restriction group (29%). The intermittent fasters also snuck food that was not provided as part of the study, suggesting that eating just 25% of energy needs every other day was too difficult for many of them.[9]

On average, the daily calorie restriction and the alternate-day groups lost the same amount of weight at month 6 (which was followed by a weight-maintenance phase): 6.8% of body weight. Changes in blood pressure, heart rate, triglyceride, fasting glucose, fasting insulin, insulin resistance, C-reactive protein, and homocysteine concentrations at months 6 and 12 were not significantly different between either intervention groups or compared with the control group. The results might have been different if more of the participants had unhealthy levels of these biomarkers at baseline, the researchers noted.[9]

Varady has since pursued research aimed at figuring out whether some categories of people might benefit more from intermittent fasting than others. Traditional calorie restriction might work well for people who are good at counting calories, she says. But “a lot of people get burned out recording their food every day with an app or calorie counter,” she says. “Intermittent fasting allows them to eat throughout the day.”

Some of the interest in intermittent fasting has come from people who are essentially healthy but hope to prolong their lives. People should avoid intermittent fasting if they are pregnant, lactating, very old, very young, or frail, or if they have solid organ transplants or are otherwise immune-compromised, says Horne.

As for people who are healthy, the evidence for an extreme regimen isn’t there yet, Longo says. Instead, for this population, he recommends restricting eating to 12 hours a day. This moderate regimen is not demanding, and because most people keep eating over the course of 15 hours a day, this could be a relatively easy way for them to avoid the overeating so common in developed countries, he says. And it could put them more in synch with circadian rhythms, which some studies have suggested could be beneficial.[2]

“A 12-hour period seems to be keeping up with our [evolutionary] history,” he says. “We probably only ate when it was light out for many reasons.” On the other hand, confining calorie intake to a shorter period—such as only 8 hours a day—could lead people to skip breakfast, which may be harmful, he says.

Varady demurs, pointing out that the evidence on breakfast is mixed. And some studies of 8-hour time-restricted feeding show benefits for people wanting to lose weight.[10]

“People just need to try out different ones and see what they can stick to,” says Varady. “At one point, I felt like we were trying to find the best diet out there,” she says. “But now we’re realizing that there is no best diet.”

Fasting boosts stem cells’ regenerative capacity .


A drug treatment that mimics fasting can also provide the same benefit, study finds
Age-related declines in stem cell function can be reversed by a 24-hour fast, according to a new study. Biologists found fasting dramatically improves stem cells’ ability to regenerate, in both aged and young mice.

Intestinal stem cells from mice that fasted for 24 hours, at right, produced much more substantial intestinal organoids than stem cells from mice that did not fast, at left.
 

As people age, their intestinal stem cells begin to lose their ability to regenerate. These stem cells are the source for all new intestinal cells, so this decline can make it more difficult to recover from gastrointestinal infections or other conditions that affect the intestine.

This age-related loss of stem cell function can be reversed by a 24-hour fast, according to a new study from MIT biologists. The researchers found that fasting dramatically improves stem cells’ ability to regenerate, in both aged and young mice.

In fasting mice, cells begin breaking down fatty acids instead of glucose, a change that stimulates the stem cells to become more regenerative. The researchers found that they could also boost regeneration with a molecule that activates the same metabolic switch. Such an intervention could potentially help older people recovering from GI infections or cancer patients undergoing chemotherapy, the researchers say.

“Fasting has many effects in the intestine, which include boosting regeneration as well as potential uses in any type of ailment that impinges on the intestine, such as infections or cancers,” says Omer Yilmaz, an MIT assistant professor of biology, a member of the Koch Institute for Integrative Cancer Research, and one of the senior authors of the study. “Understanding how fasting improves overall health, including the role of adult stem cells in intestinal regeneration, in repair, and in aging, is a fundamental interest of my laboratory.”

David Sabatini, an MIT professor of biology and member of the Whitehead Institute for Biomedical Research, is also a senior author of the paper, which appears in the May 3 issue of Cell Stem Cell.

“This study provided evidence that fasting induces a metabolic switch in the intestinal stem cells, from utilizing carbohydrates to burning fat,” Sabatini says. “Interestingly, switching these cells to fatty acid oxidation enhanced their function significantly. Pharmacological targeting of this pathway may provide a therapeutic opportunity to improve tissue homeostasis in age-associated pathologies.”

The paper’s lead authors are Whitehead Institute postdoc Maria Mihaylova and Koch Institute postdoc Chia-Wei Cheng.

Boosting regeneration

For many decades, scientists have known that low caloric intake is linked with enhanced longevity in humans and other organisms. Yilmaz and his colleagues were interested in exploring how fasting exerts its effects at the molecular level, specifically in the intestine.

Intestinal stem cells are responsible for maintaining the lining of the intestine, which typically renews itself every five days. When an injury or infection occurs, stem cells are key to repairing any damage. As people age, the regenerative abilities of these intestinal stem cells decline, so it takes longer for the intestine to recover.

“Intestinal stem cells are the workhorses of the intestine that give rise to more stem cells and to all of the various differentiated cell types of the intestine. Notably, during aging, intestinal stem function declines, which impairs the ability of the intestine to repair itself after damage,” Yilmaz says. “In this line of investigation, we focused on understanding how a 24-hour fast enhances the function of young and old intestinal stem cells.”

After mice fasted for 24 hours, the researchers removed intestinal stem cells and grew them in a culture dish, allowing them to determine whether the cells can give rise to “mini-intestines” known as organoids.

The researchers found that stem cells from the fasting mice doubled their regenerative capacity.

“It was very obvious that fasting had this really immense effect on the ability of intestinal crypts to form more organoids, which is stem-cell-driven,” Mihaylova says. “This was something that we saw in both the young mice and the aged mice, and we really wanted to understand the molecular mechanisms driving this.”

Metabolic switch

Further studies, including sequencing the messenger RNA of stem cells from the mice that fasted, revealed that fasting induces cells to switch from their usual metabolism, which burns carbohydrates such as sugars, to metabolizing fatty acids. This switch occurs through the activation of transcription factors called PPARs, which turn on many genes that are involved in metabolizing fatty acids.

The researchers found that if they turned off this pathway, fasting could no longer boost regeneration. They now plan to study how this metabolic switch provokes stem cells to enhance their regenerative abilities.

They also found that they could reproduce the beneficial effects of fasting by treating mice with a molecule that mimics the effects of PPARs. “That was also very surprising,” Cheng says. “Just activating one metabolic pathway is sufficient to reverse certain age phenotypes.”

The findings suggest that drug treatment could stimulate regeneration without requiring patients to fast, which is difficult for most people. One group that could benefit from such treatment is cancer patients who are receiving chemotherapy, which often harms intestinal cells. It could also benefit older people who experience intestinal infections or other gastrointestinal disorders that can damage the lining of the intestine.

The researchers plan to explore the potential effectiveness of such treatments, and they also hope to study whether fasting affects regenerative abilities in stem cells in other types of tissue.


Journal Reference:

  1. Maria M. Mihaylova, Chia-Wei Cheng, Amanda Q. Cao, Surya Tripathi, Miyeko D. Mana, Khristian E. Bauer-Rowe, Monther Abu-Remaileh, Laura Clavain, Aysegul Erdemir, Caroline A. Lewis, Elizaveta Freinkman, Audrey S. Dickey, Albert R. La Spada, Yanmei Huang, George W. Bell, Vikram Deshpande, Peter Carmeliet, Pekka Katajisto, David M. Sabatini, Ömer H. Yilmaz. Fasting Activates Fatty Acid Oxidation to Enhance Intestinal Stem Cell Function during Homeostasis and Aging. Cell Stem Cell, 2018; 22 (5): 769 DOI: 10.1016/j.stem.2018.04.001

Fasting Reduces Your Cardiovascular Risk


Intermittent energy restriction diets such as the 5:2 diet clears fat from the blood quicker after eating meals compared with daily calorie restriction diets, reducing an important risk factor for cardiovascular disease, a new study in the British Journal of Nutrition reports.

Intermittent fasting allows the body to use fat as it’s primary source of energy instead of sugar and there are five huge benefits.

In the first study of its kind, researchers from the University of Surrey examined the impact of the 5:2 diet on the body’s ability to metabolise and clear fat and glucose after a meal and compared it to the effects of weight-loss achieved via a more conventional daily calorie restriction diet. Previous studies in this field have predominantly focused on blood risk markers taken in the fasted state, which only tend to be, in for the minority of the time, overnight.

The simplicity of the diet and the fact you can eat pretty much what you like five days a week, are key to its popularity. Dieters are recommended to consume a ‘normal’ number of calories five days a week and then, for two, non-consecutive days, eat just 25% of their usual calorie total – 500 calories for women and 600 for men.

There are no restrictions on the types of food you can eat and it is suggested that women can expect to lose about a 1lb a week on the diet with men losing about the same if not a little more.

During the study, overweight participants were assigned to either the 5:2 diet or a daily calorie restriction diet and were required to lose five per cent of their weight. Those on the 5:2 diet ate normally for five days and for their two fasting days consumed 600 calories, using LighterLife Fast Foodpacks, whilst those on the daily diet were advised to eat 600 calories less per day than their estimated requirements for weight maintenance (in the study women ate approx. 1400 calories, men ate approx. 1900 calories/day).

Under the expert guidance of the team, those on the 5:2 diet achieved 5 per cent weight-loss in 59 days compared to those on the daily calorie restriction diet who took in 73 days. 27 participants completed the study, with approximately 20 per cent of participants in both groups dropped out because they either could not tolerate the diet or were unable to attain their 5 per cent weight-loss target.

Researchers found that following weight-loss, participants who followed the 5:2 diet cleared the fat (triglyceride) from a meal given to them more efficiently than the participants undertaking the daily diet. Although there were no differences in post meal glucose handling, researchers were surprised to find differences between the diets in c-peptide (a marker of insulin secretion from the pancreas) following the meal, the significance of which will need further investigation.

The study also found a greater reduction in systolic blood pressure (the pressure in your blood vessels when your heart beats) in participants on the 5:2 diet. Systolic blood pressure was reduced by 9% of following the 5:2, compared to a small 2% increase among those on the daily diet. A reduction in systolic blood pressure reduces pressure on arteries, potentially lessening incidences of heart attacks and strokes.

Dr Rona Antoni, Research Fellow in Nutritional Metabolism at the University of Surrey, said:

“As seen in this study, some of our participants struggled to tolerate the 5:2 diet, which suggests that this approach is not suited to everybody; ultimately the key to dieting success is finding an approach you can sustain long term.

“But for those who do well and are able stick to the 5:2 diet, it could potentially have a beneficial impact on some important risk markers for cardiovascular disease, in some cases more so than daily dieting. However, we need further studies to confirm our findings, to understand the underlying mechanisms and to improve the tolerability of the 5:2 diet.”

The Health Benefits of Intermittent Fasting


 

By Dr. Joseph Mercola

Guest Writ

The Health Benefits of Intermittent Fasting

Is it a good idea to “starve” yourself just a little bit each day, or a couple of days a week? Mounting evidence indicates that yes, intermittent fasting (IF) could have a very beneficial impact on your health and longevity.

I believe it’s one of the most powerful interventions out there if you’re struggling with your weight and related health issues. One of the primary reasons for this is because it helps shift your body from burning sugar/carbs to burning fat as its primary fuel.

As discussed in the featured article,[1] intermittent fasting is not about binge eating followed by starvation, or any other extreme form of dieting. Rather what we’re talking about here involves timing your meals to allow for regular periods of fasting.

I prefer daily intermittent fasting, but you could also fast a couple of days a week if you prefer, or every other day. There are many different variations.

To be effective, in the case of daily intermittent fasting, the length of your fast must be at least 16 hours. This means eating only between the hours of 11am until 7pm, as an example. Essentially, this equates to simply skipping breakfast, and making lunch your first meal of the day instead.

You can restrict it even further — down to six, four, or even two hours if you want, but you can still reap many of these rewards by limiting your eating to an eight-hour window each day.

This is because it takes about six to eight hours for your body to metabolize your glycogen stores; after that you start to shift to burning fat. However, if you are replenishing your glycogen by eating every eight hours (or sooner), you make it far more difficult for your body to use your fat stores as fuel.

Intermittent Fasting — More a Lifestyle Than a Diet

I have been experimenting with different types of scheduled eating for the past two years and currently restrict my eating to a 6- to 7-hour window each day. While you’re not required to restrict the amount of food you eat when on this type of daily scheduled eating plan, I would caution against versions of intermittent fasting that gives you free reign to eat all the junk food you want when not fasting, as this seems awfully counterproductive.

Also, according to research published in 2010,[2] intermittent fasting with compensatory overeating did not improve survival rates nor delay prostate tumor growth in mice. Essentially, by gorging on non-fasting days, the health benefits of fasting can easily be lost. If so, then what’s the point?

I view intermittent fasting as a lifestyle, not a diet, and that includes making healthy food choices whenever you do eat. Also, proper nutrition becomes even more important when fasting, so you really want to address your food choices before you try fasting.

This includes minimizing carbs and replacing them with healthful fats, like coconut oil, olive oil, olives, butter, eggs, avocados, and nuts. It typically takes several weeks to shift to fat burning mode, but once you do, your cravings for unhealthy foods and carbs will automatically disappear. This is because you’re now actually able to burn your stored fat and don’t have to rely on new fast-burning carbs for fuel. Unfortunately, despite mounting evidence, many health practitioners are still reluctant to prescribe fasting to their patients. According to Brad Pilon, author of Eat Stop Eat:[3]

“Health care practitioners across the board are so afraid to recommend eating less because of the stigma involved in that recommendation, but we are more than happy to recommend that someone start going to the gym. If all I said was you need to get to the gym and start eating healthier, no one would have a problem with it. When the message is not only should you eat less, you could probably go without eating for 24 hours once or twice a week, suddenly it’s heresy.”

The Health Benefits of Intermittent Fasting

Aside from removing your cravings for sugar and snack foods and turning you into an efficient fat-burning machine, thereby making it far easier to maintain a healthy body weight, modern science has confirmed there are many other good reasons to fast intermittently. For example, research presented at the 2011 annual scientific sessions of the American College of Cardiology in New Orleans[4] showed that fasting triggered a 1,300 percent rise of human growth hormone (HGH) in women, and an astounding 2,000 percent in men.

HGH, human growth hormone, commonly referred to as “the fitness hormone,” plays an important role in maintaining health, fitness and longevity, including promotion of muscle growth, and boosting fat loss by revving up your metabolism. The fact that it helps build muscle while simultaneously promoting fat loss explains why HGH helps you lose weight without sacrificing muscle mass, and why even athletes can benefit from the practice (as long as they don’t overtrain and are careful about their nutrition). The only other thing that can compete in terms of dramatically boosting HGH levels is high-intensity interval training. Other health benefits of intermittent fasting include:

Normalizing your insulin and leptin sensitivity, which is key for optimal health Improving biomarkers of disease
Normalizing ghrelin levels, also known as “the hunger hormone” Reducing inflammation and lessening free radical damage
Lowering triglyceride levels Preserving memory functioning and learning

Intermittent Fasting is as Good or Better Than Continuous Calorie Restriction

According to Dr. Stephen Freedland, associate professor of urology and pathology at the Duke University Medical Center, “undernutrition without malnutrition” is the only experimental approach that consistently improves survival in animals with cancer, as well as extends lifespan overall by as much as 30 percent.[5] Interestingly enough, intermittent fasting appears to provide nearly identical health benefits without being as difficult to implement and maintain. It’s easier for most people to simply restrict their eating to a narrow window of time each day, opposed to dramatically decreasing their overall daily calorie intake.

Mark Mattson, senior investigator for the National Institute on Aging, which is part of the US National Institutes of Health (NIH), has researched the health benefits of intermittent fasting, as well as the benefits of calorie restriction. According to Mattson,[6] there are several theories to explain why fasting works:

“The one that we’ve studied a lot, and designed experiments to test, is the hypothesis that during the fasting period, cells are under a mild stress, and they respond to the stress adaptively by enhancing their ability to cope with stress and, maybe, to resist disease… There is considerable similarity between how cells respond to the stress of exercise and how cells respond to intermittent fasting.”

In one of his studies,[7] overweight adults with moderate asthma lost eight percent of their body weight by cutting their calorie intake by 80 percent on alternate days for eight weeks. Markers of oxidative stress and inflammation also decreased, and asthma-related symptoms improved, along with several quality-of-life indicators.

More recently, Mattson and colleagues compared the effectiveness of intermittent fasting against continuous calorie restriction for weight loss, insulin sensitivity and other metabolic disease risk markers. The study, published in the International Journal of Obesity in 2011,[8] found that intermittent fasting was as effective as continuous calorie restriction for improving all of these issues, and slightly better for reducing insulin resistance. According to the authors:

“Both groups experienced comparable reductions in leptin, free androgen index, high-sensitivity C-reactive protein, total and LDL cholesterol, triglycerides, blood pressure and increases in sex hormone binding globulin, IGF binding proteins 1 and 2. Reductions in fasting insulin and insulin resistance were modest in both groups, but greater with IER [intermittent fasting] than with CER [continuous energy restriction].”

How Intermittent Fasting Benefits Your Brain

Your brain can also benefit from intermittent fasting. As reported in the featured article:

“Mattson has also researched the protective benefits of fasting to neurons. If you don’t eat for 10–16 hours, your body will go to its fat stores for energy, and fatty acids called ketones will be released into the bloodstream. This has been shown to protect memory and learning functionality, says Mattson, as well as slow disease processes in the brain.”

Besides releasing ketones as a byproduct of burning fat, intermittent fasting also affects brain function by boosting production of a protein called brain-derived neurotrophic factor (BDNF). Mattson’s research suggests that fasting every other day (restricting your meal on fasting days to about 600 calories), tends to boost BDNF by anywhere from 50 to 400 percent,[9] depending on the brain region. BDNF activates brain stem cells to convert into new neurons, and triggers numerous other chemicals that promote neural health. This protein also protects your brain cells from changes associated with Alzheimer’s and Parkinson’s disease.

BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation. (The neuromotor is the most critical element in your muscle. Without the neuromotor, your muscle is like an engine without ignition. Neuro-motor degradation is part of the process that explains age-related muscle atrophy.) So BDNF is actively involved in both your muscles and your brain, and this cross-connection, if you will, appears to be a major part of the explanation for why a physical workout can have such a beneficial impact on your brain tissue — and why the combination of intermittent fasting with high intensity exercise appears to be a particularly potent combination.

Give Intermittent Fasting a Try

If you’re ready to give intermittent fasting a try, consider skipping breakfast, make sure you stop eating and drinking anything but water three hours before you go to sleep, and restrict your eating to an 8-hour (or less) time frame every day. In the 6-8 hours that you do eat, have healthy protein, minimize your carbs like pasta, bread, and potatoes and exchange them for healthful fats like butter, eggs, avocado, coconut oil, olive oil and nuts — essentially the very fats the media and “experts” tell you to avoid.

This will help shift you from carb burning to fat burning mode. Once your body has made this shift, it is nothing short of magical as your cravings for sweets, and food in general, rapidly normalizes and your desire for sweets and junk food radically decreases if not disappears entirely.

Remember it takes a few weeks, and you have to do it gradually, but once you succeed and switch to fat burning mode, you’ll be easily able to fast for 18 hours and not feel hungry. The “hunger” most people feel is actually cravings for sugar, and these will disappear, as if by magic, once you successfully shift over to burning fat instead.

Another phenomenal side effect/benefit that occurs is that you will radically improve the beneficial bacteria in your gut. Supporting healthy gut bacteria, which actually outnumber your cells 10 to one, is one of the most important things you can do to improve your immune system so you won’t get sick, or get coughs, colds and flus. You will sleep better, have more energy, have increased mental clarity and concentrate better. Essentially every aspect of your health will improve as your gut flora becomes balanced.

Based on my own phenomenal experience with intermittent fasting, I believe it’s one of the most powerful ways to shift your body into fat burning mode and improve a wide variety of biomarkers for disease. The effects can be further magnified by exercising while in a fasted state. For more information on that, please see my previous article High-Intensity Interval Training and Intermittent Fasting – A Winning Combo.

Clearly, it’s another powerful tool in your box to help you and your family take control of your health, and an excellent way to take your fitness to the next level.

Video: Dr. Mercola: The Benefits of Intermittent Fasting

Article References

High-Intensity Interval Training and Intermittent Fasting – A Winning Combo for Fat Reduction and Optimal Fitness


If you’re still not doing interval training, you’re likely wasting an awful lot of time in the gym. This is one of the most important developments in fitness science that I can think of, as you can reap far greater health benefits in less time.

Interval Training

Story at-a-glance

  • When combined, high intensity exercise and intermittent fasting can be a winning strategy to bring your fitness to the next level
  • Recent research demonstrates that restricting carbohydrates can help burn calories more efficiently and increase muscle oxidative potential even in highly trained athletes
  • High intensity interval training has also been shown to burn more calories in less time
  • Examining data from participants in the reality TV show “The Biggest Loser,” researchers found that diet alone was responsible for more weight loss than exercise, but only 65 percent of that weight loss was body fat. The remaining 35 percent reduction in total body weight was a reduction in lean muscle mass. Exercise alone resulted in fat loss only, along with a small increase in lean muscle mass

But I’ve recently also started talking about the potential health benefits of intermittent fasting and working out in a fasted state (i.e. skipping breakfast before hitting the gym).

When you exercise while fasting, it essentially forces your body to shed fat, as your body’s fat burning processes are controlled by your sympathetic nervous system (SNS), and your SNS is activated by exercise and lack of food. The combination of fasting and exercising maximizes the impact of cellular factors and catalysts (cyclic AMP and AMP Kinases), which force the breakdown of fat and glycogen for energy.

Evidence is indeed mounting in support of this strategy, and I believe it could be quite beneficial, provided you’ve already made some fundamental lifestyle changes with regards to diet and exercise.

When combined, high-intensity exercise and intermittent fasting could very well be a winning strategy to bring your fitness to the next level.

Keep in mind that fasting, or exercising in a fasted state, would be unwise if you’re still eating a diet full of processed foods, so addressing your diet is absolutely crucial before you venture into any kind of fasting. Also, when undertaking any kind of calorie restriction, such as intermittent fasting or simply skipping breakfast, it’s critical to cut the right calories, namely carbohydrates (those from sugars and grains that is, NOT vegetable carbs).

Carb Restriction May Improve Performance in Elite Athletes

A recent study from the Swedish School of Sport and Health Sciences1 shows that restricting carbohydrates can help burn calories more efficiently and increase muscle oxidative potential even in highly trained athletes.

Ten elite level cyclists performed one hour of interval training at approximately 64 percent of maximal aerobic capacity with either low or normal muscle glycogen levels, achieved by prior exercise or diet intervention. Muscle biopsies were taken before and three hours after exercise. Results showed that exercising in a glyocogen depleted state increased mitochondrial biogenesis. (Mitochondrial biogenesis is the process by which new mitochondria are formed in your cells.)

According to the authors:

“We conclude that exercise with low glycogen levels amplifies the expression of the major genetic marker for mitochondrial biogenesis in highly trained cyclists. The results suggest that low glycogen exercise may be beneficial for improving muscle oxidative capacity.”

Part of what makes working out in a fasted state so effective is that your body actually has a preservation mechanism that protects your active muscle from wasting itself. So if you don’t have sufficient fuel in your system when you exercise, you’re going to break down other tissues but not the active muscle, i.e. the muscle being exercised.

According to fitness expert Ori Hofmekler, author of The Warrior Diet, you can quite literally re-design your physique using a combination of under-eating and exercise. However this really only works well once you’ve become fat-adapted, meaning your metabolism has become proficient at burning fat. To learn more about this, please see my other recent article on this topic, What Does it Mean to Be Fat-Adapted?

Interval Training Burns More Calories in Less Time

In related news, research presented at the Integrative Biology of Exercise VI meeting2 in Colorado on October 10-13 this year, demonstrated that high-intensity interval training burns more calories in less time – a mere 2.5 minutes, divided into five 30-second sprint intervals at maximum exertion, each followed by four minutes of light pedaling to recuperate, can burn as much as 220 calories. All in all, in less than 25 minutes total, you can burn more calories than you would if you were cycling at a moderate pace for half an hour.

According to lead researcher, exercise physiology graduate student Kyle Sevits:3

“‘You burn a lot of calories in a very short time… Nearly all the calories are burned in those 2.5 minutes; you burn very few during the rest period.’ He also points to additional benefits that come from interval training, including increased insulin sensitivity and glucose tolerance, both of which are important for overall good health.”

High-intensity interval training, which is part of my total Peak Fitness program, has also been shown to produce greater health benefits overall than conventional aerobic training. Back in April, I reported on a study that found doing just three minutes of high-intensity training per week for four weeks, could lead to significant changes in important health indices, including a 24 percent improvement in insulin sensitivity.

Another important benefit of high-intensity interval training is its ability to naturally increase your body’s production of human growth hormone (HGH), also known as “the fitness hormone.” HGH is a synergistic, foundational biochemical underpinning that promotes muscle and effectively burns excessive fat. It also plays an important part in promoting overall health and longevity. This is something you cannot get from conventional, aerobic endurance training.

How to Maximize the Health Benefits of Peak Fitness Training

While it’s theoretically possible to reap valuable results with as little as three minutes (plus rest periods in between spurts) once a week, it would be more beneficial doing them two or three times a week for a total of four minutes of intense exertion per session, especially if you are not doing strength training. You do not need to do high-intensity exercises more often than that however. In fact, doing it more frequently than two or three times a week can be counterproductive, as your body needs to recover between sessions.

Intensity is KEY for reaping all the benefits interval training can offer. To perform it correctly, you’ll want to raise your heart rate to your anaerobic threshold, and to do that, you have to give it your all for those 20 to 30 second intervals. Different studies will use different intervals of exertion and recuperation. For example, in the featured study on elite athletes, bouts of exertion were separated by four-minute rest intervals. They also didn’t “max out” during the exertion phase.

I use and recommend the program developed by Phil Campbell, which will trigger HGH production as you go “all out” during the exertion phase. Here’s a summary of what a typical interval routine might look like using an elliptical:

  • Warm up for three minutes.
  • Exercise as hard and fast as you can for 30 seconds. You should be gasping for breath and feel like you couldn’t possibly go on another few seconds. It is better to use lower resistance and higher repetitions to increase your heart rate.
  • Recover for 90 seconds, still moving, but at slower pace and decreased resistance.
  • Repeat the high-intensity exercise and recovery 7 more times.

When you’re first starting out, depending on your level of fitness, you may only be able to do two or three repetitions of the high-intensity intervals. As you get fitter, just keep adding repetitions until you’re doing eight during your 20-minute session. Once you regularly incorporate these 20-minute exercises about twice a week, most people notice the following benefits:

Decrease in body fat Improved muscle tone
Improved athletic speed and performance Ability to achieve your fitness goals much faster
Increase in energy and sexual desire Firmer skin and reduced wrinkles

Exercise is Key for Reducing Body Fat While Preserving Your Muscle

I’ve frequently stated that 80 percent of the health benefits you reap from a healthy lifestyle come from your diet, and the remaining 20 percent from exercise. However, it’s important to realize that there is a profound synergy between the two, as yet another recent study demonstrates.

The researchers examined data from 11 participants in the reality TV show “The Biggest Loser.” Total body fat, total energy expenditure, and resting metabolic rate were measured three times: at the start of the program, six weeks into the program, and at week 30, which was at least four months after participants returned home. Using a mathematical computer model of human metabolism, the researchers calculated the impact of the diet and exercise changes resulting in weight loss, to evaluate the relative contributions of each.

Interestingly, while diet alone was calculated to be responsible for more weight loss overall than exercise, only 65 percent of that weight loss was body fat. The remaining 35 percent reduction in total body weight was a reduction in lean muscle mass. Exercise alone resulted in fat loss only, along with a small increase in lean muscle mass. According to the National Institutes of Health press release:4

“The simulations also suggest that the participants could sustain their weight loss and avoid weight regain by adopting more moderate lifestyle changes – like 20 minutes of daily vigorous exercise and a 20 percent calorie restriction – than those demonstrated on the television program.”

Tips for Fasting and Exercising Safely: A Post-Workout Recovery Meal is Crucial

An effective exercise program that incorporates high-intensity interval training combined with intermittent fasting can help counteract muscle aging and wasting, and boost fat-burning. If at any point you don’t have enough energy or don’t feel good, then it is likely time to shift your experiment and reduce the hours of fasting. Intermittent fasting should make you feel better, and if it doesn’t then it is best to reevaluate your strategy.

Make sure to keep the following two points in mind:

1. Timing of meals: Intermittent fasting is not extreme calorie restriction. You’re not supposed to starve yourself. Rather it’s simply a matter of timing your meals properly by abstaining from food during much of the day, and limiting your eating to a small window later in the evening. If you were to limit eating to say 4-7 pm, you are effectively fasting for 21 hours. Ideally, you’ll want to fast for at least 12-18 hours.

If you can’t abstain from food entirely during the day, limit it to small servings of light, low-glycemic, mostly raw foods such as fruits, vegetables, whey protein or lightly poached eggs every 4-6 hours. Whatever times you choose, it will be very helpful to avoid having any food or calories for three hours prior to going to bed as this will minimize oxidative damage to your system and give your body a major jumpstart in intermittent fasting.

2. Break your fast with a recovery meal on workout days: On the days that you work out while fasting, you need to consume a recovery meal 30 minutes after your workout. Fast-assimilating whey protein is ideal. Then fast again until you eat your main meal at night. It’s very important that you eat an appropriate recovery meal after your workout session, as this will prevent brain and muscle damage from occurring, so do NOT skip this meal.

If the thought of fasting for 12-18 hours is too much, you can get many of the same benefits of fasting and exercise by simply skipping breakfast and exercising first thing in the morning when your stomach is empty. This is because eating a full meal, particularly carbohydrates, before your workout will inhibit your sympathetic nervous system and reduce the fat burning effect of your exercise. Instead, eating lots of carbs activates your parasympathetic nervous system, (which promotes energy storage – the complete opposite of what you’re aiming for).

Intermittent Fasting Beats Traditional Diets and Even Chronic Calorie Restriction for Weight Loss and Other Health Benefits


Intermittent fasting or “scheduled eating” is one of the most powerful interventions I know of to shed excess weight and reduce your risk of chronic diseases like diabetes and heart disease.

Intermittent Fasting

Story at-a-glance

  • Intermittent fasting or “scheduled eating” is a powerful strategy for shedding excess weight and reducing your risk of chronic diseases like diabetes, heart disease, and cancer
  • Three major mechanisms by which fasting benefits your body include increased insulin sensitivity and mitochondrial energy efficiency; reduced oxidative stress; and increased capacity to resist stress, disease, and aging
  • A recent human study confirmed that intermittent fasting was actually more effective for weight loss and improving insulin resistance than daily calorie restriction
  • Intermittent fasting can also dramatically boost human growth hormone production, reduce inflammation, and lessen free radical damage—all of which have beneficial effects on your health
  • To get started, consider skipping breakfast, and avoid eating at least three hours before you go to sleep. This should effectively restrict your eating to an 8-hour window or less each day

These health benefits are more or less beneficial “side effects” of shifting your body from burning sugar to burning fat as its primary fuel. I’m really pleased to see this approach now receiving more mainstream media attention, as it’s such a potent health-promoting tool.

Most recently, The Wall Street Journal1 did a write-up on intermittent calorie restriction, specifically mentioning the 5:2 diet, promoted by Dr. Michael Mosley2 in his book The Fast Diet: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting.

The 5:2 strategy involves eating regularly five days a week, and fasting for two. On fasting days, Dr. Mosley recommends cutting your food down to ¼ of your normal daily calories, or about 600 calories for men and about 500 for women, along with plenty of water and tea.

As reported by featured article:

“Some research shows that this more radical-sounding approach may be a struggle at first but ends up being easier to stick with compared with the typical route of cutting calories each day. Some animal studies suggest it also offers other health benefits, including cognitive improvements.”

There are many different variations of intermittent fasting, however. If you are like 85 percent of the population and have insulin resistance, my personal recommendation is to fast every day by simply scheduling my eating into a narrower window of time each day. I find this method to be easier than fasting for a full 24 hours or more, twice a week.

Once you are at your ideal body weight, don’t have diabetes, high blood pressure, or abnormal cholesterol levels, you can eat more at other times. However, it is probably best to regularly resume some type of scheduled eating regimen on a regular basis.

‘Intermittent Eating’ May Be Easier Than Day-Long Fasts

In order to understand how you can fast daily while still eating every day, you need to understand some basic facts about metabolism. It takes most people eight to 12 hours for their body to burn the sugar stored in your body as glycogen. Now, most people never deplete their glycogen stores because they eat three or more meals a day. This teaches your body to burn sugar as your primary fuel and effectively shuts off your ability to use fat as a fuel.

Therefore, in order to work, the length of your fast must be at least eight hours. Still, this is a far cry from a 24-hour or longer fast, which can be quite challenging. I believe that, for most people, simply restricting the window of time during which you eat your food each day is far easier.

For example, you could restrict your eating to the hours of 11am and 7pm. Essentially, you’re just skipping breakfast and making lunch your first meal of the day instead. This equates to a daily fasting of 16 hours—twice the minimum required to deplete your glycogen stores and start shifting into fat burning mode.

Please keep in mind that a proper nutrition plan becomes even more important when you’re fasting and/or cutting calories, so you really want to address your food choices before you try any form of fasting.

This includes minimizing carbs and replacing them with healthful fats, like coconut oil, olive oil, olives, butter, eggs, avocados, and nuts. Many would benefit from getting as much as 50-85 percent of their daily calories from fats. (While this may sound like a lot, consider that, in terms of volume, the largest portion of your plate would be vegetables, since they contain so few calories. Fat, on the other hand, tends to be very high in calories. For example, just one tablespoon of coconut oil is about 130 calories—all of it from healthful fat.)

Three Reasons Why Intermittent Fasting Works

One of the primary mechanisms that makes intermittent fasting so beneficial for health is related to its impact on your insulin sensitivity. While sugar is a source of energy for your body, it also promotes insulin resistance when consumed in the amounts found in our modern processed food diets. Insulin resistance, in turn, is a primary driver of chronic disease—from heart disease to cancer. Mounting research confirms that when your body becomes accustomed to burning FAT instead of sugar as its primary fuel, you rather dramatically reduce your risk of chronic disease. Becoming fat adapted may even be a key strategy for both cancer prevention and treatment, as cancer cells cannot utilize fat for fuel—they need sugar to thrive.

In short, fasting increases insulin sensitivity along with mitochondrial energy efficiency, thereby retarding aging and disease, which are typically associated with loss of insulin sensitivity and declined mitochondrial energy. Two additional mechanisms by which fasting benefits your body include:

1. Reducing oxidative stress

Fasting decreases the accumulation of oxidative radicals in the cell, and thereby prevents oxidative damage to cellular proteins, lipids, and nucleic acids associated with aging and disease.

2. Increasing capacity to resist stress, disease and aging

Fasting induces a cellular stress response (similar to that induced by exercise) in which cells up-regulate the expression of genes that increase the capacity to cope with stress and resist disease and aging.

Watch Cravings ‘Magically’ Vanish While Excess Weight Falls Off…

Intermittent fasting is one of the most effective ways I know of to shed excess weight. And, although it might be challenging in the beginning, once you’ve adapted to burning fat, you’ll typically find that sugar cravings vanish without a trace.

The featured article3 cites a recent study4 comparing the effectiveness of intermittent fasting versus daily calorie restriction to produce weight loss in overweight women with a history of breast cancer. All in all, intermittent fasting was determined to be more effective for weight loss and improving insulin resistance than daily calorie restriction:

“Participants were divided into groups and instructed to eat a diet for three months in a way that reduced their typical calorie intake by about 25 percent. The first group ate only low-carbohydrate foods for two consecutive days, while the second was limited to two straight days of low-carbohydrate, low-calorie foods. The third group restricted calories daily.

The two intermittent restriction groups lost twice as much weight as the chronic restriction group, but the intermittent groups didn’t differ from each other. In addition, more people in the intermittent groups lost weight: 65 percent of intermittent restrictors, compared with 40 percent in the chronic restriction group.”

Keep in mind that while most people will successfully switch over to burning fat after several weeks of intermittent fasting, you may need several months to teach your body to turn on the fat-burning enzymes that allow your body to effectively use fat as its primary fuel. So don’t give up!

Once you’ve become fat adapted and are of a normal weight, without high blood pressure, diabetes, or high cholesterol, you really only need to do scheduled eating occasionally. As long as you maintain your ideal body weight, you can go back to eating three meals a day if you want to. I restricted my eating to a six- to seven-hour window each day until I got fat adapted and lost about 10 pounds. Now, I still rarely ever eat breakfast, but several days a week I will have two meals instead of just one.

Other Health Benefits of Intermittent Fasting

Aside from removing your cravings for sugar and snack foods and turning you into an efficient fat-burning machine, modern science has confirmed there are many other good reasons to fast intermittently. For example, research presented at the 2011 annual scientific sessions of the American College of Cardiology in New Orleans5 showed that fasting triggered a 1,300 percent rise of human growth hormone (HGH) in women, and an astounding 2,000 percent in men.

HGH, commonly referred to as “the fitness hormone” plays an important role in maintaining health, fitness, and longevity, including promotion of muscle growth, and boosting fat loss by revving up your metabolism.

The fact that it helps build muscle while simultaneously promoting fat loss explains why HGH helps you lose weight without sacrificing muscle mass, and why even athletes can benefit from the practice (as long as they don’t over train and are careful about their nutrition). The only other thing that can compete in terms of dramatically boosting HGH levels is high-intensity interval training. Other health benefits of intermittent fasting include:

Normalizing your insulin  and leptin sensitivity, which is key for optimal health Improving biomarkers of disease
Normalizing ghrelin levels, also known as “the hunger hormone” Reducing inflammation and lessening free radical damage
Lowering triglyceride levels Preserving memory functioning and learning

Intermittent Fasting May Boost Your Brain Health

With Alzheimer’s incidence on the rise, it’s well worth noting strategies that can help prevent such a fate, and intermittent fasting appears to be a particularly effective one. As reported in the featured article:

“… [F]asting for periods of as short as 16 to 24 hours seems to induce a state of mild stress in the body. The brain releases additional neurotrophic proteins that help stimulate and support the growth of neurons and other cells, heightening their responsiveness and activity. Just as exercise makes muscles stronger, fasting makes the brain stronger, Dr. Mattson says. The body chemicals produced by fasting and exercise also could help boost people’s moods.”

The brain-boosting protein referred to here is called brain-derived neurotrophic factor (BDNF). Dr. Mattson, mentioned in the paragraph above, is a senior investigator for the National Institute on Aging, which is part of the US National Institutes of Health (NIH). He has researched the health benefits of both intermittent fasting and calorie restriction, and his research suggests that fasting every other day can boost BDNF by anywhere from 50 to 400 percent,6 depending on the brain region.

This is great news, as BDNF activates brain stem cells to convert into new neurons, and triggers numerous other chemicals that promote neural health. This protein also protects your brain cells from changes associated with Alzheimer’s and Parkinson’s disease.

Interestingly, BDNF also expresses itself in the neuro-muscular system where it protects neuro-motors from degradation. (The neuromotor is the most critical element in your muscle. Without the neuromotor, your muscle is like an engine without ignition. Neuro-motor degradation is part of the process that explains age-related muscle atrophy.) So BDNF is actively involved in both your muscles and your brain, and this cross-connection helps explain why a physical workout can have such a beneficial impact on your brain tissue—and why the combination of intermittent fasting with high intensity interval training appears to be a particularly potent health-boosting combination.

Are You Ready to Boost Your Health Potential?

Based on my own phenomenal experience with scheduled eating, I believe it’s one of the most powerful ways to shift your body into fat burning mode and improve a wide variety of biomarkers for disease. The effects can be further magnified by exercising while in a fasted state. For more information on that, please see my previous article “High-Intensity Interval Training and Intermittent Fasting – A Winning Combo.”

To get started, consider skipping breakfast, and avoid eating at least three hours before you go to sleep. This should effectively restrict your eating to an 8-hour window or less each day.

When you do eat, make sure to minimize carbs like pasta, bread, and potatoes. Instead, exchange them for healthful fats like butter, eggs, avocado, coconut oil, olive oil, and nuts—essentially the very fats the media and “experts’ tell you to avoid. You may also want to restrict your protein a bit if you’re typically a big meat eater. I strongly suggest eating only high-quality pastured protein, and limiting it to about one gram of protein per kilogram of lean body mass (about one-half gram of protein per pound of lean body weight) may be appropriate for most people. (Note: if your body fat mass is 20 percent, your lean mass is 80 percent of your total body weight.)

These kinds of food choices, in combination with intermittent fasting, will help shift you from carb burning to fat burning mode. Last but not least, intermittently fasting will also help support healthy microorganisms in your gut. Your intestinal health, as you may know, in turn has a tremendous influence on your overall health, as 80 percent of your immune system resides in your gut.

Remember, it usually does take a few weeks, and you have to do it gradually, but once you succeed to switch to fat burning mode, you’ll be easily able to fast for 18 hours and not feel hungry. The “hunger” most people feel are actually cravings for sugar, and these will disappear, as if by magic, once you successfully shift over to burning fat instead of sugar.

Some caveats: If you’re hypoglycemic, diabetic, or pregnant (and/or breastfeeding), you are better off avoiding any type of fasting or timed meal schedule until you’ve normalized your blood glucose and insulin levels, or weaned the baby. Other categories of people that would be best served to avoid fasting include those living with chronic stress and those with cortisol dysregulation.

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