There is nothing new, except what has been forgotten.
MARIE ANTOINETTE
LONG-TERM DIETING IS futile. After the initial weight loss, the dreaded plateau appears, followed by the even more dreaded weight regain. The body reacts to weight loss by trying to return to its original body set weight. We hope our body set weight will decrease over time, but that hoped-for reduction does not materialize. Even if we eat all the right things, our insulin levels stay elevated.
But we’ve been addressing only half of the problem. Long-term weight loss is really a two-step process. Two major factors maintain our insulin at a high level. The first is the foods that we eat—which are what we usually change when we go on a diet. But we fail to address the other factor: the long-term problem of insulin resistance. This problem is one of meal timing.
Insulin resistance keeps our insulin levels high. High insulin maintains our high body set weight. Inexorably, our high body set weight erodes our weight-loss efforts. We start feeling hungrier. Our metabolism (that is, our total energy expenditure) relentlessly decreases until it falls below the level of our energy intake. Our weight plateaus and ruthlessly climbs back up to our original body set weight, even as we keep dieting. Clearly, changing what we eat is not always enough.
To succeed, we must break the insulin-resistance cycle. But how? The body’s knee-jerk reaction to insulin resistance is to increase insulin levels, which, in turn, creates even more resistance. To break the insulin-resistance cycle, we must have recurrent periods of very low insulin levels. (Remember that resistance depends on having both persistent and high levels.)
But how can we induce our body into a temporary state of very low insulin levels?
We know that eating the proper foods prevents high levels, but it won’t do much to lower them. Some foods are better than others; nonetheless, all foods increase insulin production. If all foods raise insulin, then the only way for us to lower it is to completely abstain from food. The answer we are looking for is, in a word, fasting.
When we talk about fasting to break insulin resistance and lose weight, we are talking about intermittent fasts of twenty-four to thirty-six hours. A practical plan for accomplishing these fasts is included in appendix B. The remainder of this chapter will be devoted to addressing the health concerns around fasting—which, the research shows us, is a beneficial practice.
FASTING: AN ANCIENT REMEDY
INSTEAD OF SEARCHING for some exotic, never-seen-before diet miracle to help us break insulin resistance, let’s instead focus on a tried-and-true ancient healing tradition. Fasting is one of the oldest remedies in human history and has been part of the practice of virtually every culture and religion on earth.
Whenever fasting is mentioned, there is always the same eye-rolling response: Starvation? That’s the answer? No. Fasting is completely different. Starvation is the involuntary absence of food. It is neither deliberate nor controlled. Starving people have no idea when and where their next meal will come from. Fasting, however, is the voluntary abstinence from food for spiritual, health or other reasons. Fasting may be done for any period of time, from a few hours to a few months. In a sense, fasting is part of everyday life. The term “breakfast” is the meal that breaks the fast—which we do daily. As a healing tradition, fasting has a long history. Hippocrates of Kos (c. 460–c. 370 BC) is widely considered the father of modern medicine. Among the treatments that he prescribed and championed were the practice of fasting and the consumption of apple cider vinegar. Hippocrates wrote, “To eat when you are sick, is to feed your illness.” The ancient Greek writer and historian Plutarch (c. AD 46–c. AD 120) also echoed these sentiments. He wrote, “Instead of using medicine, better fast today.” Plato and his student Aristotle were also staunch supporters of fasting.
The ancient Greeks believed that medical treatment could be discovered by observing nature. Humans, like most animals, do not eat when they become sick. Consider the last time you were sick with the flu. Probably the last thing you wanted to do was eat. Fasting seems to be a universal human response to multiple forms of illnesses and is ingrained in human heritage, as old as mankind itself. Fasting is, in a sense, an instinct.
The ancient Greeks believed that fasting improved cognitive abilities. Think about the last time you ate a huge Thanksgiving meal. Did you feel more energetic and mentally alert afterward? Or instead, did you feel sleepy and a little dopey? More likely the latter. Blood is shunted to your digestive system to cope with the huge influx of food, leaving less blood for brain function. Fasting does the opposite, leaving more blood for your brain.
Other intellectual giants were also great proponents of fasting. Paracelsus (1493–1541), the founder of toxicology and one of the three fathers of modern Western medicine (along with Hippocrates and Galen), wrote, “Fasting is the greatest remedy—the physician within.” Benjamin Franklin (1706–90), one of America’s founding fathers and renowned for wide knowledge, once wrote of fasting, “The best of all medicines is resting and fasting.”
Fasting for spiritual purposes is widely practiced and remains part of virtually every major religion in the world. Jesus Christ, Buddha and the prophet Muhammed all shared a common belief in the power of fasting. In spiritual terms, it is often called cleansing or purification; in practical terms, it amounts to the same thing. The practice of fasting developed independently among different religions and cultures, not as something that was harmful, but something that was deeply, intrinsically beneficial to the human body and spirit.1 In Buddhism, food is often consumed only in the morning, and followers fast daily from noon until the next morning. In addition to this, there may be various water-only fasts for days or weeks on end. Greek Orthodox Christians may follow various fasts over 180–200 days of the year. Dr. Ancel Keys often considered Crete the poster child for the healthy Mediterranean diet. However, there was a critically important factor that he completely dismissed. Most of the population of Crete followed the Greek Orthodox tradition of fasting.
Muslims fast from sunrise to sunset during the holy month of Ramadan. The prophet Muhammad also encouraged fasting every week on Mondays and Thursdays. Ramadan differs from many fasting protocols in that fluids, in addition to food, are forbidden, so practitioners of this particular fast undergo a period of mild dehydration. Further, since eating is permitted before sunrise and after sunset, recent studies 2 indicate that daily caloric intake actually rises significantly during this period. Gorging, particularly on highly refined carbohydrates, before sunrise and after sunset negates much of fasting’s benefit.
THE BODY’S RESPONSE TO FASTING
GLUCOSE AND FAT are the body’s main sources of energy. When glucose is not available, then the body adjusts by using fat, without any health detriment.
This compensation is a natural part of life. Periodic food scarcity has always been part of human history, and our bodies have evolved processes to deal with this fact of Paleolithic life. The transition from the fed state to the fasted state occurs in several stages:3
1. Feeding: During meals, insulin levels are raised. This allows glucose uptake by tissues such as the muscle or brain for direct use as energy. Excess glucose is stored as glycogen in the liver.
2. The post-absorptive phase (six to twenty-four hours after fasting starts): Insulin levels being to fall. The breakdown of glycogen releases glucose for energy. Glycogen stores last for roughly twenty-four hours.
3. Gluconeogenesis (twenty-four hours to two days): The liver manufactures new glucose from amino acids and glycerol. In non- diabetic persons, glucose levels fall but stay within the normal range.
4. Ketosis (one to three days after fasting starts): The storage form of fat, triglycerides, is broken into the glycerol backbone and three fatty acid chains. Glycerol is used for gluconeogenesis. Fatty acids may be used for directly for energy by many tissues in the body, but not the brain. Ketone bodies, capable of crossing the blood-brain barrier, are produced from fatty acids for use by the brain. Ketones can supply up to 75 percent of the energy used by the brain.4 The two major types of ketones produced are beta hydroxybutyrate and acetoacetate, which can increase more than seventy-fold during fasting.5
5. Protein conservation phase (after five days): High levels of growth hormone maintain muscle mass and lean tissues. The energy for maintenance of basal metabolism is almost entirely met by the use of free fatty acids and ketones. Increased norepinephrine (adrenalin) levels prevent the decrease in metabolic rate.
The human body is well adapted for dealing with the absence of food.
What we’re describing here is the process the body undergoes to switch from burning glucose (short term) to burning fat (long term). Fat is simply the body’s stored food energy. In times of food scarcity, stored food (fat) is naturally released to fill the void. The body does not “burn muscle” in an effort to feed itself until all the fat stores are used.
It’s crucial to note that all these beneficial adaptive changes do not occur in the caloric-reduction diet strategy.
HOW YOUR HORMONES ADAPT TO FASTING
Insulin
FASTING IS THE most efficient and consistent strategy to decrease insulin levels, a fact first noted decades ago6 and widely accepted as true. All foods raise insulin; therefore, the most effective method of reducing insulin is to avoid all foods. Blood glucose levels remain normal as the body switches over to burning fat for energy. This effect occurs with fasting periods as short as twenty-four to thirty-six hours.