The Obesity Code: Unlocking the Secrets of Weight Loss (Why Intermittent Fasting Is the Key to Controlling Your Weight)

by Jason Fung

EXCESS CALORIES MAY certainly be the proximate cause of weight gain, but not its ultimate cause. What’s the difference between proximate and ultimate? The proximate cause is immediately responsible, whereas the ultimate cause is what started the chain of events.

Childhood obesity is associated with a 200 percent to 400 percent increased risk of adult obesity.

Dietary and lifestyle habits have changed considerably since the 1970s including •adoption of a low-fat, high-carbohydrate diet, •increased number of eating opportunities per day, •more meals eating out, •more fast-food restaurants, •more time spent in cars and vehicles, •increased popularity of videos games, •increased use of computers, •increase in dietary sugar, •increased use of high-fructose corn syrup and •increased portion sizes. Any

We obsess about caloric input into the system, but output is far more important. What determines the energy output of the system? Suppose we consume 2000 calories of chemical energy (food) in one day. What is the metabolic fate of those 2000 calories? Possibilities for their use include •heat production, •new protein production, •new bone production, •new muscle production, •cognition (brain), •increased heart rate, •increased stroke volume (heart), •exercise/physical exertion, •detoxification (liver), •detoxification (kidney), •digestion (pancreas and bowels), •breathing (lungs), •excretion (intestines and colon) and •fat production.

Calories Out is highly dependent on Calories In.

In response to caloric reduction, metabolism decreases almost immediately, and that decrease persists more or less indefinitely.

In other words, it is harder for people who have lost weight to resist food.15 This has nothing whatsoever to do with a lack of willpower or any kind of moral failure. It’s a normal hormonal fact of life. We feel hungry, cold, tired and depressed. These are all real, measurable physical effects of calorie restriction. Reduced metabolism and the increased hunger are not the cause of obesity—they are the result. Losing weight causes the reduced metabolism and increased hunger, not the other way around. We do not simply make a personal choice to eat more. One of the great pillars of the caloric-reduction theory of obesity—that we eat too much because we choose to—is simply not true. We do not eat too much because we choose to, or because food is too delicious, or because of salt, sugar and fat. We eat too much because our own brain compels us to.

Is exercise important in reducing childhood obesity? The short answer is no. A 2013 paper5 compared the physical activity (measured using accelerometry) of children aged three to five years to their weight. The authors concluded there is no association between activity and obesity.

Total energy expenditure = Basal metabolic rate + Thermogenic effect of food + Nonexercise activity thermogenesis + Excess post-exercise oxygen consumption + Exercise. The key point here is that total energy expenditure is not the same as exercise. The overwhelming majority of total energy expenditure is not exercise but the basal metabolic rate: metabolic housekeeping tasks such as breathing, maintaining body temperature, keeping the heart pumping, maintaining the vital organs, brain function, liver function, kidney function, etc.

Basal metabolic rate depends on many factors, including •genetics, •gender (basal metabolic rate is generally higher in men), •age (basal metabolic rate generally drops with age), •weight (basal metabolic rate generally increases with muscle mass), •height (basal metabolic rate generally increases with height), •diet (overfeeding or underfeeding), •body temperature, •external temperature (heating or cooling the body) and •organ function.

Obesity is a hormonal dysregulation of fat mass. The body maintains a body set weight, much like a thermostat in a house. When the body set weight is set too high, obesity results. If our current weight is below our body set weight, our body, by stimulating hunger and/or decreasing metabolism, will try to gain weight to reach that body set weight. Thus, excessive eating and slowed metabolism are the result rather than the cause of obesity.

Glycogen is like your wallet. Money goes in and out constantly. The wallet is easily accessible, but can only hold a limited amount of money. Fat, however, is like the money in your bank account. It is harder to access that money, but there is an unlimited storage space for energy there in your account.

The key to understanding obesity is to understand what regulates body set weight, why body set weight is set so high, and how to reset it lower.

Reducing stress is difficult, but vitally important. Contrary to popular belief, sitting in front of the television or computer is a poor way to relieve stress. Instead, stress relief is an active process. There are many time-tested methods of stress relief, including mindfulness meditation, yoga, massage therapy and exercise.

Refined carbohydrates are easy to become addicted to and overeat precisely because there are no natural satiety hormones for refined carbs. The reason, of course, is that refined carbohydrates are not natural foods but are instead highly processed. Their toxicity lies in that processing.

A diet high in foods that provoke an insulin response may initiate obesity, but over time, insulin resistance becomes a larger and larger part of the problem and can become, in fact, a major driver of high insulin levels. Obesity drives itself. A long-standing obesity cycle is extremely difficult to break, and dietary changes alone may not be sufficient.

But in the development of obesity, the increase in meals is almost twice as important as the change in diet.

Eating more frequent meals does not aid in weight loss.

“Calories” was the perfect scapegoat. Eat fewer calories, they said. But eat more of everything else. There is no company that sells “Calories,” nor is there a brand called “Calories.” There is no food called “Calories.” Nameless and faceless, calories were the ideal stooge. “Calories” could now take all the blame.

One of the worst myths is that eating more frequently causes weight loss. Eat snacks to lose weight? It sounds pretty stupid. And it is.

Does breakfast make you hungry? If you eat a slice of toast and drink a glass of orange juice in the morning—are you hungry an hour later? If so, then don’t eat breakfast. If you are hungry and want to eat breakfast, then do so. But avoid sugars and refined carbohydrates. Skipping breakfast does not give you the freedom to eat a Krispy Kreme donut as a mid-morning snack either.

should we eat more fruits and vegetables? Yes, definitely. But only if they are replacing other unhealthier foods in your diet. Replace. Not add.

The pediatrician Dr. Benjamin Spock wrote his classic bible of child rearing, Baby and Child Care, in 1946. For more than fifty years, it was the second-bestselling book in the world, after the Bible. Regarding childhood obesity, he writes, “Rich desserts can be omitted without risk, and should be, by anyone who is obese and trying to reduce. The amount of plain, starchy foods (cereals, breads, potatoes) taken is what determines . . . how much (weight) they gain or lose.”

At the liver, fructose is rapidly metabolized into glucose, lactose and glycogen. The body handles excess glucose consumption through several well-defined metabolic pathways, such as glycogen storage and de novo lipogenesis (creation of new fat). No such system is present for fructose. The more you eat, the more you metabolize. The bottom line is that excess fructose is changed into fat in the liver. High levels of fructose will cause fatty liver. Fatty liver is absolutely crucial to the development of insulin resistance in the liver.

Fructose overconsumption leads directly to insulin resistance.

Over the ten years of the Northern Manhattan Study,9 Dr. Hannah Gardener from the University of Miami found in 2012 that drinking diet soda was associated with a 43 percent increase in risk of vascular events (strokes and heart attacks).

In 2014, Dr. Ankur Vyas from the University of Iowa Hospitals and Clinics 12 presented a study following 59,614 women over 8.7 years in the Women’s Health Initiative Observational Study. The study found a 30 percent increase risk of cardiovascular events (heart attacks and strokes) in those drinking two or more diet drinks daily. The benefits for heart attack, stroke, diabetes and metabolic syndrome were similarly elusive. Artificial sweeteners are not good. They are bad. Very bad.

Caloric reduction is the main advantage of artificial sweeteners. But it is not calories that drives obesity; it’s insulin. Since artificial sweeteners also raise insulin levels, there is no benefit to using them. Eating chemicals that are not foods (such as aspartame, sucralose or acesulfame potassium) is not a good idea. They are synthesized in large chemical vats and added to foods because they happen to be sweet and not kill you. Small amounts of glue won’t kill you either. That doesn’t mean we should be eating it. The bottom line is that these chemicals do not help you lose weight and may actually cause you to gain it. They may cause cravings that induce overeating of sweet foods. And continually eating sweet foods, even if they have no calories, may lead us to crave other sweet foods.

Carbohydrates are not inherently fattening. Their toxicity lies in the way they are processed.

High-fiber foods require more chewing, which may help to reduce food intake. Horace Fletcher (1849–1919) believed strongly that chewing every bite of food 100 times would cure obesity and increase muscle strength. Doing so helped him lose 40 pounds (18 kilograms), and “Fletcherizing” became a popular weight-loss method in the early twentieth century.

In short, fiber may decrease food intake, slow down food’s absorption in the stomach and small intestine, then help it exit quickly through the large intestines—all of which are potentially beneficial in treating obesity.

WHEN WE CONSIDER the nutritional benefits of food, we typically consider the vitamins, minerals and nutrients contained. We think about components in the food that nourish the body. Such is not the case for fiber. The key to understanding fiber’s effect is to realize that it is not as a nutrient, but as an anti-nutrient—where its benefit lies. Fiber has the ability to reduce absorption and digestion. Fiber subtracts rather than adds. In the case of sugars and insulin, this is good. Soluble fiber reduces carbohydrate absorption, which in turn reduces blood glucose and insulin levels.

Removing protein and fat in the diet may lead to overconsumption. There are natural satiety hormones (peptide YY, cholecystokinin) that respond to protein and fat. Eating pure carbohydrate does not activate these systems and leads to overconsumption (the second-stomach phenomenon).

Two teaspoons of vinegar taken with a high-carbohydrate meal lowers blood sugar and insulin by as much as 34 percent, and taking it just before the meal was more effective than taking it five hours before meals.

The insulin index, created by Susanne Holt in 1997, measures the rise in insulin in response to a standard portion of food, and it turns out to be quite different from the glycemic index.2 Not surprisingly, refined carbohydrates cause a surge in insulin levels. What was astounding was that dietary proteins could cause a similar surge. The glycemic index does not consider protein or fats at all because they do not raise glucose, and that approach essentially ignores the fattening effects of two out of the three major macronutrients. Insulin can increase independently of blood sugar.

All foods, not just carbohydrates, stimulate insulin. Thus, all foods can cause weight gain. And hence we get major confusion with calories. High-protein foods can cause weight gain—not due to their caloric content, but rather to their insulin-stimulating effects. If carbohydrates are not the only or even the major stimulus to insulin, then restricting carbohydrates may not always be as beneficial as we believed. Substituting insulin-stimulating proteins for insulin-stimulating carbohydrates produces no net benefit. Dietary fat, though, tends to have the weakest insulin-stimulating effect.

PROTEINS DIFFER GREATLY in their capacity to stimulate insulin,8 with dairy products in particular being potent stimuli.9 Dairy also shows the largest discrepancy between the blood glucose and insulin effect. It scores extremely low on the glycemic index (15 to 30), but very high on the insulin index (90 to 98). Milk does contain sugars, predominantly in the form of lactose. However, when tested, pure lactose has minimal effect on either the glycemic or insulin indexes.

Higher and higher amounts of fat do not stimulate any greater insulin response. Despite the higher caloric value of fat, it stimulates insulin less than carbohydrates or protein.

Second, while we understand the benefits of eating “whole” foods, we do not apply this knowledge to meat. We eat only the muscle meats rather than the entire animal, thereby risking overconsumption of the muscle meats. We generally discard most of the organ meats, cartilage and bones—which is analogous to drinking the juice of a fruit but discarding the pulp. Yet bone broth, liver, kidney and blood are all parts of the traditional human diets. Traditional staples like steak-and-kidney pie, blood sausage and liver have disappeared. Ethnic foods such as tripe, pork bung, congealed pig’s blood, oxtail and beef tongue still survive. The organ meats tend to be the fattiest parts of the animal. By focusing almost exclusively on the muscles of animals for food, we are preferentially eating protein rather than fat.

Therefore, even if dairy proteins are particularly good at stimulating insulin, the small portions do not make a large overall difference.

Animal protein is highly variable but comes with the protective effect of satiety. And we shouldn’t ignore the protective power of the incretin effect. The slowing of gastric motility increases satiety so that we feel more full and therefore eat less at the next meal, or even skip a meal altogether to allow ourselves “time to digest.” This behavior is instinctive. When children are not hungry, they will not eat. Wild animals also show the same restraint. But we’ve trained ourselves to ignore our own feelings of satiety so that we will eat when the time comes, whether we are hungry or not.

Here’s a small tip for weight loss, one that should be obvious, but is not. If you are not hungry, don’t eat. Your body is telling you that you should not be eating.

There are no intrinsically bad foods, only processed ones. The further you stray from real food, the more danger you are in. Should you eat protein bars? No. Should you eat meal replacements? No. Should you drink meal replacement shakes? Absolutely not. Should you eat processed meats, processed fats or processed carbohydrates? No, no and no.

Heart attacks and strokes are predominantly inflammatory diseases, rather than simply diseases of high cholesterol levels.

High dietary ratios of omega 6:3 ratios increase inflammation, potentially worsening cardiovascular disease. It is estimated that humans evolved eating a diet that is close to equal in omega 6 and 3 fatty acids.9 However, the current ratio in the Western diet is closer to a 15:1 to 30:1 ratio. Either we are eating way too little omega 3, way too much omega 6, or more likely, both. In 1990, the Canadian nutritional guidelines were the first to recognize the important difference and include specific recommendations for both types of fatty acids. Animal fats had been replaced by highly inflammatory omega 6–laden vegetable oils that had been widely advertised as “heart healthy.” This is ironic since atherosclerosis is now considered mostly to be an inflammatory disease.

A ten-year study in Oahu, Hawaii,27 found a protective effect of saturated fat on stroke risk. The twenty-year follow-up data from the Framingham study confirmed these benefits.28 Those eating the most saturated fat had the least strokes, but polyunsaturated fats (vegetable oils) were not beneficial. Monounsaturated fats (olive oil) were also protective against stroke, a consistent finding throughout the decades.

So all diets fail. The question is why. Permanent weight loss is actually a two-step process. There is a short-term and a long-term (or time-dependent) problem. The hypothalamic region of the brain determines the body set weight—the fat thermostat. (For more on body set weight, see chapters 6 and 10.) Insulin acts here to set body set weight higher. In the short term, we can use various diets to bring our actual body weight down. However, once it falls below the body set weight, the body activates mechanisms to regain that weight—and that’s the long-term problem.

The truth is that there are multiple overlapping pathways that lead to obesity. The common uniting theme is the hormonal imbalance of hyper-insulinemia. For some patients, sugar or refined carbohydrates are the main problem. Low-carbohydrate diets may work best here. For others, the main problem may be insulin resistance. Changing meal timing or intermittent fasting may be most beneficial. For still others, the cortisol pathway is dominant. Stress reduction techniques or correcting sleep deprivation may be critical. Lack of fiber may be the critical factor for yet others.

STEP 1: REDUCE YOUR CONSUMPTION OF ADDED SUGARS

Almost ubiquitous in refined and processed foods, sugar is not always labeled as such. Other names include sucrose, glucose, fructose, maltose, dextrose, molasses, hydrolyzed starch, honey, invert sugar, cane sugar, glucose-fructose, high fructose corn syrup, brown sugar, corn sweetener, rice/corn/cane/maple/malt/golden/palm syrup and agave nectar.