The world’s oldest diet may be your solution to a leaner physique.
Sometimes the easiest conclusion is the hardest to find. In the quest to lose body fat, we have become convinced that we must hack our own biology. We try to outwit our metabolism and stay one step ahead of our genes. We manipulate our hormones and stop just short of putting Groucho glasses on our food in order to disguise the calories from our own bodies.
What if getting shredded didn’t take these sleights of the biochemical hand? What if the answer to dropping pounds was as simple as this: Stop eating?
The idea of going without food is as depressing as it is counterintuitive. After all, regular feeding stokes fat-burning metabolism and pumps valuable amino acids into hungry muscles, right? While this eat-every-three-hours strategy has worked for many, the idea of getting lean by constantly consuming calories does seem a bit like trying to clean a stained-glass window with a bucket full of rocks. The alternative is called intermittent fasting.
What Is “IF”?
Intermittent fasting, popularly referred to as “IF,” is the consistent use of 16–24-hour periods of zero caloric intake. (Well, not exactly zero. See “Safe Cheating.”) It has been gaining popularity with people whose weight-loss efforts have either stalled or never taken off in the first place. Adherents of IF report decreases in body-fat levels, surges in growth-hormone release, improved markers of cardiovascular health, decreased muscle inflammation, and even a renewed appreciation for the smell and taste of food. Another positive side effect is being cured of the pervasive fear of hunger and the belief that forgoing food for several hours is injurious.
“If you look at human evolution, you’ll see how hearty we had to be to come from the plains of Africa, which is probably some of the hardest terrain on human beings there is,” says Stu White, co-founder of Bodyworks Lifestyle in Huntington Beach, Calif., and the nutrition consultant to UFC middleweight contender Mark Munoz. “Going 24 hours without food will not kill you.”
A Surge of Growth Hormone
The health and longevity benefits of caloric restriction are some of the few findings in nutrition science that are considered to be boilerplate. The daily calorie consumption of the longest-living and most disease-free cultures on the planet is significantly less than that of the average North American. Thousands of studies have shown that when placed on a calorie-restricted diet, animals invariably outlive their better-fed counterparts and have less incidents of cancer. A study published last year in the journal Nutrition and Metabolism showed that subjects who underwent an IF-style diet enjoyed significant protection from coronary heart disease.
The question then becomes: Who wants to live forever if you have the muscle mass of Gandhi and the testosterone levels of Barbara Walters? This image of a stick-figure ascetic is woefully outdated. The fact is, the relatively short duration of an intermittent fast leads to very little muscle loss and sets in motion a hormonal chain of events that not only burns fat, but also protects hard-earned muscle.
“You are definitely not going to lose a lot of muscle when you do an intermittent fast,” says Amy Kubal, RD, owner of the nutrition consulting business Fuel as RX in Austin, Texas. “Your body has stores of fat that it will feed off of; it won’t take fuel directly from your muscles. Your body will use stored glycogen in your liver, stored glycogen in your muscles, and tap into your fat reserves for energy. IF gets your body to use those stores because you are not giving your body carbs every few hours, so it forces you to burn fat.”
A study conducted by the Department of Kinesiology and Nutrition at the University of Illinois at Chicago examined the weight-loss results in subjects who either underwent daily caloric restriction, such as in a traditional diet, and those who performed IF. At the end of the study, both groups experienced similar decreases in body weight and fat mass, but the IF groups retained more of their muscle.
The secret to the muscle-sparing effects of IF is a massive surge in growth hormone that occurs in the body after approximately 16–24 hours in a fasted state. A study presented at the annual scientific sessions of the American College of Cardiology in New Orleans showed that during 24-hour fasting periods, human growth hormone increased an average of 1,300% in women and nearly 2,000% in men. Human growth hormone helps build muscles, accelerates metabolic rate, speeds recovery time, and is also known to spare muscle tissue during periods of fasting.
“If you are fasting, you aren’t going to have an insulin response, so growth hormone levels will stay high, which is absolutely killer for fat mobilization,” says White. “That is a big factor why fasting once a week will burn very little muscle but help you get rid of body fat. Fasting for a week would be a different story, but a short-term fast is a huge help for dropping body fat.”
Fast Start
IF can be performed in a number of ways, but in the last few years, two distinct versions have become popular. The first is a simple 24-hour fast once a week. The second is a daily 14–16-hour fast, in which you keep your eating to a strict eight-hour window every day. Both methods combine the same fat-burning and GH-boosting benefits with a meal-at-the-end-of-the-tunnel motivation that you don’t get when on a traditional daily diet.
“My clients tend to like the 16-hour fasts,” says Kubal. “It is basically skipping breakfast. You stop eating at 8 p.m. and don’t eat until noon the next day. Anytime you can minimize that insulin rise, it’s a good thing. But 24 hours is a long time. What I tell people is that if you are starving and miserable, then don’t do it. If you are driving to work and feeling dizzy, that isn’t good for anyone.”
The ongoing 16-hour fasts, popularized by Martin Berkhan of leangains.com, are more of a permanent lifestyle shift than a sporadic intervention. Since most people find it easier to fast in the morning and go to bed feeling satisfied, it’s easiest to begin at night and break the fast in the early afternoon. White, on the other hand, likes the detoxifying benefits of a 24-hour fast.
“When we fast, it gives our organs and digestive system a chance to rest. This is an important and often overlooked health aspect. When we exercise, we take days off completely. Why wouldn’t other bodily mechanisms benefit from the same thing?” asks White. “When the body is fasting, it allows for detoxification, especially if plenty of water is consumed. I prefer raw vegetable juice, which will speed up the detox of the liver and help purge toxins faster.”
White suggests fasting on Sundays, so you won’t fall prey to the stress of a workday. If you can sleep for more than eight hours, you will keep your cortisol levels low, which will help mitigate muscle loss.
Before undertaking any version of IF, a few dietary changes must be made to increase the chances of success. If you need to gobble a rice cracker every two hours lest you get light-headed and irritable, 16–24 hours of fasting is going to be a miserable experience. IF works best for those on a Paleo-style high-protein/moderate-fat/low-carb diet.
“If your diet is not good in the first place, you have no business messing with intermittent fasting,” says Kubal. “Eat real food and avoid processed, packaged crap. Eat pastured and grass-fed meats, lots of veggies and healthy fats such as coconut oil, olive oil and avocados. Some fruit is OK, but it shouldn’t be the bulk of your diet.”
This type of diet will make you less susceptible to insulin spikes and blood-sugar swings. The fat and protein in your last meal will also keep you satisfied for much longer than a carb-heavy meal.
“You should eat protein and fat and as many green vegetables as you can stomach for the three to four days leading up to a fast,” says White. “Free- range protein, healthy fats and vegetables will keep you insulin-sensitive. If you are insulin-resistant, you will have a much harder time fasting.”
End With a Bang
Each intermittent fast ends with the potential of a big anabolic payoff. To take advantage of the massive surge in GH that occurs after 16 hours of fasting, IF experts recommend hitting the weights in the last hour of your fast. Your postworkout recovery meal is what breaks the fast. Not only will your muscles make use of the growth hormone circulating through your system, but they also will partition the nutrients from the recovery meal to your muscle fibers and glycogen stores.
Working out after going hungry for the better part of a day may sound like torture, but it works. A study published in the European Journal of Applied Physiology examined two groups of subjects who were given a protein/carb concoction after a workout in the weight room. The group who trained in a fasted state experienced a much greater anabolic response from the postworkout meal than the group who ate a carb-heavy breakfast prior to training.
“If your primary goal is to rip as much fat from your body as possible, then working out in a fasted state is a great solution,” says White.
Remember, IF isn’t for everybody. Pregnant women, nursing women, children and diabetics should not attempt to fast. Athletes interested in performance will probably not see a game-day spike in their abilities from fasting (although White insists they would get a health boost from the detoxification process).
“If you are under a lot of stress or your sleep is off, then not eating is an additional stress,” says Kubal. “Your cortisol levels will already be high, and then you’ll start releasing more cortisol. It will turn into this whole cascade of releasing insulin, which is a fat-storage hormone. In that case, intermittent fasting can work against you.”
As long as your diet is buttoned up and your stress is managed, IF might be the technique that helps you break through that fat-loss plateau.
Safe Cheating
A few loopholes do exist in the intermittent fasting food code. Drinking plenty of liquids is encouraged as long as they are not insulinogenic, meaning they do not cause insulin levels to rise. (That means, no protein and absolutely zero carbs.) Water and green tea are commonly consumed during a fast, but three other options can help your body detoxify, preserve muscle and lose fat, while delivering a modicum of satiety and variety.
Green Juice:
Nutrition consultant Stu White believes that freshly blended raw vegetables can help speed detoxification and provide some valuable nutrients during a fast. “If you go with celery, cucumber, spinach, kale and a little bit of lemon, there will be very little insulin response,” he says. If it’s not possible to get fresh, raw, organic juice, White recommends using a supergreen powder.
Branched-chain Amino Acids:
Valine, isoleucine and especially leucine initiate protein synthesis and curb protein breakdown without causing an insulin release. BCAAs can also be used for energy during your workouts. Take 10 g just prior to or during your fasted training and another 10 g immediately afterward, unless you can eat a whole-food meal right away.
Coffee:
Giving up coffee in a fast would be a deal-breaker for many, not to mention foolish. A study published in the American Journal of Physiology showed that the metabolic rate of a fasting subject is significantly increased when exposed to epinephrine, a chemical in your body that is released when you ingest caffeine.
A supercharged version of java known as Bulletproof Coffee has enjoyed a cultlike following among IF enthusiasts. Simply combine two cups of high-quality organic coffee that ideally comes from a single source in Central America and has been roasted very recently (wet-roasted, preferably). When blended with 2 tablespoons of unsalted, grass-fed butter and 1–2 tablespoons of MCT (medium chain triglyceride) oil, it is said to provide increased mental focus and abundant energy for training.
“MCTs get metabolized more like glucose, so you get some energy from the coffee,” says Amy Kubal, RD, who thinks Bulletproof Coffee should be used sparingly. “It is about 200 calories a cup. You won’t get an insulin response, but the bulk of the population doesn’t need that many fat calories.”
Mike Carlson is a certified personal trainer through the National Academy of Sports Medicine, a CrossFit Level One Trainer and an Ironman triathlon finisher. He is currently an editor at UFC 360 magazine.