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While the worldwide economic crisis is making headlines, another crisis is occurring—one that may not make the morning news but is more alarming than international money woes. The lesser-known crisis involves health. In short, many people are getting fatter. Along with increased bodyfat comes increased incidence of most degenerative diseases, such as cardiovascular disease, cancer and arthritis, all of which are directly related to how much bodyfat you carry. Type 2 diabetes used to be called “adult-onset diabetes” because the disease usually began around age 40. Not only are cases of diabetes worldwide increasing exponentially, but even more alarmingly, type 2 diabetes is showing up in much younger people. Studies have found early signs of it in children as young as 12.While the worldwide economic crisis is making headlines, another crisis is occurring—one that may not make the morning news but is more alarming than international money woes. The lesser-known crisis involves health. In short, many people are getting fatter. Along with increased bodyfat comes increased incidence of most degenerative diseases, such as cardiovascular disease, cancer and arthritis, all of which are directly related to how much bodyfat you carry. Type 2 diabetes used to be called “adult-onset diabetes” because the disease usually began around age 40. Not only are cases of diabetes worldwide increasing exponentially, but even more alarmingly, type 2 diabetes is showing up in much younger people. Studies have found early signs of it in children as young as 12.

The most common advice for offsetting the rising trend of obesity is to increase physical activity and improve diet and nutrition. The latter aspect, however, is fraught with controversy. While age-old physical laws suggest that you need to reduce total daily calories to lose bodyfat, some challenge those laws, stating that the source of calories determines how much and how effectively you lose bodyfat. Adding to the confusion is the plethora of diets available, from lowfat to high-fat plans and much in between. Some say to limit protein intake, while others say that increased protein is vital for maintaining lean mass. On the other hand, if you separate the political and commercial aspects of all diets, the common factor is a reduction in total calories.

Given that fact, wouldn’t reducing total calories to zero, as in fasting, be the most effective diet of all? At first, the concept of not eating anything seems ludicrous. After all, the body is like a machine, and like all machines it runs best on a certain fuel mixture. In the case of the human body, the mixture consists of a balance of protein, fat and carbohydrate. While protein and two types of fatty acids are essential to health, carbohydrate isn’t. That’s because your body can synthesize glucose—the most elemental form of carbohydrate in the body and the only sugar it requires to run efficiently—from amino acids, which are metabolic products of protein, and fat.

Short-term fasting, such as the kind associated with religious practices, doesn’t produce negative health effects. Islam reserves the month of Ramadan for fasting from sunrise to sunset. While Ramadan fasting offers some clues into the effects of food deprivation, various studies have demonstrated that despite not eating all day, Muslims who fast get the same number of daily calories, or even more, during the fasting periods. They eat more during the hours when they’re not fasting. Still, the lack of calories for so many hours does provide some insight into what happens when you drastically reduce food intake.

What Happens During Food Deprivation?

Perhaps the most controlled experiment involving food deprivation was the “Minnesota Experiment,” which was conducted by Dr. Ancel Keys from November 19, 1944, to December 20, 1945. The researchers wanted to ascertain the effects of severe undernutrition on the physiology and psychology of humans, and their subjects were 36 male conscientious objectors, aged 20 to 33, who ate 40 percent fewer calories than usual for 168 days. The lack of food resulted in an average 24 percent loss of bodyweight. The most interesting aspect of the study, however, occurred when the starvation period ended. The prisoners were permitted to eat as much as they wanted, and not unexpectedly, the men were ravenously hungry. They overate enough to not only put back the lost weight but also exceed their initial bodyfat levels, an effect Dr. Keys called “post-starvation obesity.”

Studies of famine and prisoners of war have found that women withstand semistarvation better than men. Because they have more bodyfat relative to men, women can tap into their stores more efficiently during fasting and starvation conditions. That makes it easier for them, because fat is the most concentrated source of calories at nine per gram and thus is a potent energy source—at least for a time.

One study documented the effects of a hunger strike on a man.1 It was a more realistic, though tragic, look at what happens during a long-term fast. The man lost 40 percent of his initial bodyweight and died after 63 days. At the time of his death he weighed only 70 pounds. Irish prisoners went on a hunger strike in 1981, dying of starvation after 57 to 73 days. Studies with animals show that normal-weight animals die when there is a loss of 40 to 50 percent of initial bodyweight. Again, however, how fast you die from not eating depends on your bodyfat. Fat or “overbulked” bodybuilders can derive some solace from the fact that they are physically superior to the average Mr. Olympia contestant: The limited bodyfat in competitive bodybuilders would doom them to die more quickly from starvation than their fatter peers.

One scientist calculated that a lean person would survive for 60 to 70 days without food, while a fat person could last for 200 to 300 days. In one case study involving two morbidly obese female patients, the subjects survived a fast lasting 249 days, or just short of a year, without any food, to lose 30 percent of their initial bodyweight. In fact, so-called therapeutic fasting in a hospital setting was an accepted type of treatment for extreme obesity in the 1950s and ’60s. The medical fasts usually lasted from 10 to 117 days. The longest recorded fast, which made it into the Guinness Book of World Records, involved a Scot who fasted for 382 days to achieve a loss of 75 percent of his initial weight.2

Studies of average Americans show that 14 percent have used short-term fasting for purposes of weight loss. Even so, fasting is frowned on by doctors and dietitians, who link a variety of serious complications to lack of food. They include ventricular fibrillation, a serious heart-rhythm disturbance; lactic acidosis, or an imbalance in the acid and alkaline in the body; various vitamin and mineral deficiencies; and even sudden death. On a more practical note, any type of enforced dieting involving calorie restriction has a 95 percent recidivism rate, meaning that 95 percent of dieters regain the weight they lost. The likelihood of regaining lost bodyfat is even higher when you don’t eat any food, as during a fast.

Proponents of fasting often say that it offers health benefits. Losing excess bodyfat by any means, even fasting, does attack the negative effects of being fat, such as cardiovascular disease and diabetes. Fasting advocates, however, often elevate such benefits to the metaphysical realm, suggesting that fasting enables the body to eliminate toxins, which in itself would result in a greater sense of well-being and health. In fact, the body is more than capable of eliminating toxins. The primary purpose of both the liver and kidneys is to do just that: flush out metabolic waste products and degrade toxins. The notion that you need to not eat to get those benefits is just plain wrong.

Certain changes do occur in body physiology under fasting conditions. The body contains enough stored carbohydrate in the form of glycogen to last about 12 hours with no food intake. What happens inside depends on how much bodyfat you have. Those who have limited bodyfat, such as muscular people, will begin to degrade protein stores, taken mainly from muscle. The degraded protein, in the elemental form of amino acids, will be converted in the liver into glucose in a process called gluconeogenesis. It supplies the circulating glucose required for brain and neural function. Those with higher bodyfat will begin using their stored fat as an energy source about a day after the fast begins. Those with lower bodyfat begin to tap into fat stores after about 48 hours.

As the brain registers the effects of food deprivation, certain hormone changes occur to deal with the cutoff of calories. The changes maximize the body’s use of energy stores while attempting to minimize the use of other substances that are required to preserve health and life. So within a few days active thyroid hormone is replaced by an inert form called reverse T3. That prevents the metabolism of lean tissue, mainly muscle. Muscle loss starts at the peripheral areas, such as the forearms and calves, and gradually works its way upward. The last to go are the proteins of the internal organs, such as the liver, heart and so on.

As fat is used for fuel, the liver releases large quantities of ketone bodies, which are by-products of fat metabolism. Those who have followed low-carb diets are familiar with ketones, since they also increase when carbs are restricted. Ketones can be used as an alternative fuel source for brain and muscle and even have anticatabolic activity in muscle, sparing the breakdown of muscle when calories are restricted. One particular ketone, beta-hydroxybutyrate, is linked to feelings of euphoria during both low-carb diets and fasting. That isn’t hard to understand when you realize that BHB is an isomer of the notorious substance, GHB.

Gamma-hydroxybutyric acid is linked to mental euphoria, and both it and BHB interact with a brain neurotransmitter called GABA, which is the primary inhibitory neurotransmitter of the brain. That helps explain why ketogenic diets that feature little or no carb intake appear to be effective for treating epilepsy and why those who engage in fasting often report feelings of euphoria.3

Fasting also drastically lowers resting insulin counts, which favors the use of bodyfat as fuel. One recent study found that fasting for two days resulted in an 80 percent suppressed resting insulin, accompanied by a fourfold rise in growth hormone.4 GH rises during fasting because it is a “survival” hormone needed to provide energy substrates during calorie deprivation. In this study the rate of fat breakdown after two days of fasting doubled, but protein breakdown rose by 40 percent. When a substance that blocks GH was given to subjects, the fat breakdown was completely wiped out, showing how important GH is to providing fat as fuel during a fast.

The study also found that during short-term fasting of a day or less, GH doesn’t much affect fat loss. It comes into play only during extended fasts, lasting two days or more. The initial use of fat during a fast depends on increased release of catecholamines—norepinephrine and epinephrine. That effect is short-lived, however, since the beta-adrenergic fat cell receptors rapidly become desensitized to the effects of catecholamines. That’s when GH takes over.

The researchers discovered that GH didn’t seem stop the loss of body protein during a fast. That was likely related to the drop in insulin. Insulin has anticatabolic properties in muscle, and if you’re low on it, you’ll probably lose muscle protein unless you compensate with a lot of amino acids.

Case Study of Extreme Fasting: David Blaine

David Blaine is an illusionist and stunt performer whose skills have earned him several television specials. Many of his stunts are tests of human endurance and willpower. He’s spent 61 hours encased in a block of ice, stood on a tiny platform 90 feet high for 36 hours and lived in a transparent box suspended high over the river Thames in London for 44 days, eating no food the entire time.

The box stunt began on September 5, 2003. Blaine, 30 at the time, was sealed inside a plastic case suspended 30 feet in the air. The case had a ­Webcam installed so that viewers could observe him. The idea of not eating was inspired by a 1922 short story written by Franz Kafka called, “A Hunger Artist.” He was described as a muscular man with about 20 percent bodyfat whose arm size was larger than average. The physiological results of Blaine’s sojourn in the plastic box were subsequently published.5

At the start of his fast, Blaine weighed 211 pounds. By the end of it he’d lost 25.5 percent of his body mass, or 54 pounds. Analysis of his body composition proved that a quarter to a third of the weight loss consisted of bodyfat, with the rest mostly muscle. He lost 20 percent of his total protein mass and 20 to 25 percent of his fat mass. Of the total energy expenditure he had during the fast, 13 to 17.1 percent came from oxidation of body protein, or muscle. The level of manganese, an essential trace mineral, declined in Blaine during the fast by 1.2 percent. Urinary losses accounted for 17.3 percent of his body’s selenium content and 40.5 percent of his zinc stores. By the end of his fast he had elevated blood counts of zinc and vitamin B12, with normal counts of copper, selenium and manganese. He did, however, show deficiencies of thiamine (B1), riboflavin (B2) and vitamin K.

Blaine felt weaker and more lethargic as the event progressed. After the two-week mark he experienced postural hypotension—that is, dizziness and faintness when quickly standing up. He had visual problems—as if he were blacking out, he said. Shooting pains were evident in his limbs and trunk, as well as abdominal discomfort, nausea and irregular heartbeat. After five days in the box he suffered nose bleeds. His blood pressure dropped significantly by the end of the fast. Postfasting measurements of his upper arm revealed significant loss of muscle size.

After the fast, Blaine was low on phosphorus and fluid retention, which are related to the “refeeding syndrome” that occurs after a prolonged bout of fasting. After being admitted to a hospital, Blaine was given limited calories in the form of a nutritionally complete drink, along with oral vitamin supplements. When he was admitted, Blaine had normal blood glucose, attesting to the body’s ability to control blood glucose even in the total absence of food. He did, however, show elevated blood fatty acids, along with a high ketone count.

Blaine’s body had a lot of insulinlike-growth-factor-binding protein, somatostatin and cortisol onboard but was low on insulin and very low on IGF-1. It all points to very limited GH release. While Blaine initially wasn’t hungry at the end of the fast, his normal appetite had returned by the third day of refeeding.

Blaine was a young man with moderate bodyfat and a fairly muscular build, but extended fasting resulted in a greater loss of muscle than bodyfat, along with a significant loss of essential nutrients.

Can Fasting Be Healthy?

A study of members of the Church of Jesus Christ of the Latter-day Saints, who practice intermittent fasting, found that they had a 54 percent reduced risk of cardiovascular disease. They also had reduced incidence of diabetes, although fasting didn’t affect bodyweight or blood pressure.6

Studies with animals reveal that the only effective method for maximizing life span involves calorie restriction. Most effective is reducing calorie intake an average of 30 to 40 percent. While some intrepid humans have voluntarily followed similar calorie-restriction regimens, there is as yet no definitive human evidence proving its long-term effectiveness. On the other hand, those who have the willpower to restrict their food intake stringently experience definite improvements in cardiovascular risk factors, such as lower blood pressure and blood lipids. They also have less insulin and resting blood glucose, pointing to preventive effects against diabetes.

From a bodybuilding point of view, however, the picture is considerably less positive. People who’ve practiced calorie restriction are very thin to the point of appearing emaciated. They’re always cold and have little or no energy for exercise. They are low on IGF-1 and other anabolic hormones, including testosterone. Their thyroid may be normal, although on the low end of the scale. In short, calorie restriction is definitely not conducive to adding muscle mass.

More recent studies have suggested that intermittent fasting, which involves restricting calories every other day, may provide many of the health benefits of straight calorie restriction. The fact that you can eat normally on alternate days makes such a plan far more reasonable. One study examined intermittent fasting in eight men and eight women, none of whom were obese.7 They lost 2.5 percent of their initial bodyweight over 22 days. Feelings of hunger increased on the first day of the fast and remained elevated. Fat burning gradually increased, peaking at the end of the study. The subjects also significantly dropped their resting insulin. One reported feeling light-headed once, and four others reported constipation. While no one withdrew from the study, many reported feeling irritable on their fasting days, indicating that long-term compliance wasn’t likely.

While the subjects did get some health benefits, the irritability they experienced made it as unlikely they’d stick with an intermittent-fasting regimen as they would a regular weight-loss diet. The authors suggest that one solution may be to eat a small meal on a fasting day. A study using mice as subjects found that an intermittent-fasting regimen produced changes in bodyfat distribution—less visceral fat, more fat in subcutaneous stores—similar to those that come with more traditional diets.

For those who can handle it, intermittent fasting will probably provide most, perhaps all, of the benefits associated with straight calorie restriction. Even so, it requires a great deal of willpower and motivation, for feelings of hunger and loss of energy aren’t abated by the modified plan. Short-term fasting isn’t dangerous to health, although many of the alleged health benefits are questionable. From the point of view of an activity like bodybuilding, which requires increased energy as well as an optimal anabolic hormone profile and optimal nutrient intake, fasting doesn’t offer much, if any, true benefit.


1 Meyers, A.W. (1917). Some morphological effects of prolonged inanition. J Med Res. 36:51-78.

2 Stuart, W.K., et al. (1973). Features of a successful therapeutic fast of 382 days’ duration. Postgrad Med. 49:203-209.

3 Brown, A.J. (2007). Low-carb diets, fasting and euphoria: Is there a link between ketosis and gamma-hydroxybutyrate (GHB)? Med Hypthe. 68:268-71.

4 Sakharova, A.A., et al. (2008). Role of growth hormone in regulating lipolysis, proteolysis, and hepatic glucose production during fasting. J Endocrin Metab. 93:2755-2759.

5 Jackson, J.M., et al. (2006). Macro and micronutrient losses and nutritrional status resulting from 44 days of total fasting in a non-obese man. Nutrition. 22:889-97.

6 Horne, B.D., et al. (2008). Usefulness of routine periodic fasting to lower risk of coronary artery disease in patients undergoing coronary angiography. Am J Cardiol. 102:814-819.

7 Heilbronn, L.K., et al. (2005). Alternate-day fasting in nonobese subjects: effects on bodyweight, body composition, and energy metabolism. Am J Clin Nutr. 81:69-73. IM

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