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

by Jason Fung

Fung’s novel contribution is his insight that treatment in type 2 diabetes focuses on the symptom of the disease—an elevated blood glucose concentration—rather than its root cause, insulin resistance.

Seventy percent of your tendency to gain weight is determined by your parentage. Obesity is overwhelmingly inherited.

Decreasing Calories In triggers a decrease in Calories Out.

ignores the extremely powerful effect of the body’s hormonal state. The defining characteristic of the human body is homeostasis, or adaptation to change.

The second key change is that the hormonal signals that stimulate hunger increase. The body is pleading with us to eat in order for it to regain the lost weight.

Total energy expenditure is the sum of basal metabolic rate (defined below), thermogenic effect of food, non-exercise activity thermogenesis, excess post-exercise oxygen consumption and, of course, exercise.

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),

The name leptin was derived from “lepto,” the Greek word for thin. The mechanism was very similar to that proposed decades earlier by Hervey. Higher levels of fat tissue produce higher levels of leptin. Traveling to the brain, it turns down hunger to prevent further fat storage.

Leptin is one of the primary hormones involved in weight regulation in the normal state. However, in obesity, it is a secondary hormone because it fails the causality test. Giving leptin doesn’t make people thin. Human obesity is a disease of leptin resistance, not leptin deficiency. This leaves us with much the same question that we began with. What causes leptin resistance? What causes obesity?

Hormones are molecules that deliver messages to a target cell. For example, thyroid hormone delivers a message to cells in the thyroid gland to increase its activity. Insulin delivers the message to most human cells to take glucose out of the blood to use for energy.

To deliver this message, hormones must attach to the target cell by binding to receptors on the cell surface, much like a lock and key. Insulin acts on the insulin receptor to bring glucose into the cell. Insulin is the key and fits snugly into the lock (the receptor). The door opens and glucose enters. All hormones work in roughly the same fashion. When we eat, foods

Insulin is a key regulator of energy metabolism, and it is one of the fundamental hormones that promote fat accumulation and storage. Insulin facilitates the uptake of glucose into cells for energy. Without sufficient insulin, glucose builds up in the bloodstream. Type 1 diabetes results from the autoimmune destruction of the insulin-producing cells in the pancreas, which results in extremely low levels of insulin.

Macleod were awarded the 1923 Nobel Prize in Medicine), changed this formerly fatal disease into a chronic one. At mealtimes, ingested carbohydrate leads to more glucose being available than needed. Insulin helps move this flood of glucose out of the bloodstream into storage for later use. We store this glucose by turning it into glycogen in the liver—a process called glycogenesis. (Genesis means “the creation of,” so this term means the creation of glycogen.) Glucose molecules are strung together in long chains to form glycogen. Insulin is the main stimulus of glycogenesis. We can convert glucose to glycogen and back again quite easily.

But the liver has only limited storage space for glycogen. Once full, excess carbohydrates will be turned into fat—a process called de novo lipogenesis. (De novo me...

Several hours after a meal, blood sugars and insulin levels start to drop. Less glucose is available for use by the muscles, the brain and other organs. The liver starts to break down glycogen

into glucose to release it into general circulation for energy—the glycogen-storage process in reverse. This happens most nights, assuming you don’t eat at night.

Glycogen is easily available, but in limited supply. During a short-term fast (“fast” meaning that you do not eat), your body has enough glycogen available to function. During a prolonged fast, your body can make new glucose from its fat stores—a process called gluconeogenesis (the “making of new sugar”). Fat is burned to release energy, which is then sent out to the body—the fat-storage process in reverse. Insulin is a storage hormone. Ample intake of food leads to insulin release. Insulin then t...

down and we use our stored energy. As long as our feeding and fasting periods are balanced, this system also remains balanced. If we eat breakfast at 7 a.m. and finish eating dinner at 7 p.m., the twelve hours of feeding balances the twelve hours of fasting. 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. Like the wallet, glycogen is quickly able to provide glucose to the body. However, the supply of glycogen is limited. Like the bank account, fat stores contain an unlimited amount of energy, but they are harder to access. This situation, of course, partially explains the difficulty in

losing accumulated fat. Before getting money from the bank, you spend what’s in your wallet first. But you don’t like having an empty wallet. In the same manner, before getting energy from the Fat Bank, you spend the energy in the Glycogen Wallet. But you also don’t

like an empty Glycogen Wallet. So you keep the Glycogen Wallet filled, which prevents you from accessing the Fat Bank. In other words, before you can even begin to burn fat, you start feeling hungry and anxious because your glycogen is becoming depleted. If you continually refi...

Obese patients1 tend to have a higher fasting insulin level, as well as an exaggerated insulin response to food.

CORTISOL IS THE so-called stress hormone, which mediates the flight-or-fight response, a set of physiological responses to perceived threats. Cortisol, part of a class of steroid hormones called glucocorticoids (glucose + cortex + steroid), is produced in the adrenal cortex.

Why do we care? Because insulin resistance leads to high insulin levels, and as we’ve seen, high insulin levels cause obesity.

And it’s a self-reinforcing cycle—a vicious cycle. Exposure leads to resistance. Resistance leads to higher exposure. And the cycle keeps going around. Using higher doses has a paradoxical effect. The effect of using more antibiotics is to make antibiotics less effective. The effect of using more cocaine is to make cocaine less effective. So let’s recap what we know: •Antibiotics cause antibiotic resistance. High doses cause more resistance. •Viruses cause viral resistance. High doses cause more resistance. •Drugs cause drug resistance (tolerance). High doses cause more resistance.

Insulin resistance is compartmentalized. The main compartments are the brain, liver and muscle.

High levels alone do not lead to resistance. There are two requirements for resistance—high hormonal levels and constant

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.

The pediatrician Dr. Benjamin Spock wrote his classic bible of child rearing, Baby and Child Care,

Book

GLUCOSE, A SUGAR with the basic molecular structure of a six-sided ring, can be used by virtually every cell in the body. Glucose is the main sugar found in the blood and circulates throughout the body. In the brain, it is the preferred energy source. Muscle cells will greedily import glucose from the blood for a quick energy boost. Certain cells, such as red blood cells, can only use glucose for energy. Glucose can be stored in the body in various forms such as glycogen in the liver. If glucose stores run low, the liver can make new glucose via the gluconeogenesis process (literally meaning “making new glucose”). Fructose, a sugar with the basic molecular structure of a five-sided ring, is found naturally in fruit. It is metabolized only in the liver and does not circulate in the blood. The brain, muscles and most other tissues cannot use fructose directly for energy. Eating fructose does not appreciably change the blood glucose level. Both glucose and fructose are single sugars, or monosaccharides.

Table sugar is called sucrose, and is composed of one molecule of glucose linked to one molecule of fructose. Sucrose is 50 percent glucose and 50 percent fructose. High-fructose corn syrup is composed of 55 percent fructose and 45 percent glucose. Carbohydrates are composed of sugars.

YOU WANT to avoid weight gain, remove all added sugars from your diet. On this, at least, everybody can agree.

Aspartame’s popularity has since been eclipsed by acesulfame potassium, followed by the current champion, sucralose. Diet soda is the most obvious source in our diet of these chemicals, but yogurts, snack bars, breakfast cereals and many other “sugar-free” processed foods also contain them.

Sucralose13 raises insulin by 20 percent, despite the fact that it contains no calories and no sugar. This insulin-raising effect has also been shown for other artificial sweeteners, including the “natural” sweetener stevia.

FIBER IS THE non-digestible part of food, usually of a carbohydrate. Common types of fiber include cellulose, hemicellulose, pectins, beta-glucans, fructans and gums.

Fiber may decrease the palatability of food and thus reduce food intake. Fiber bulks up foods and decreases its energy density. Soluble fiber absorbs water to form a gel, further increasing its volume. This effect helps fill the stomach, which increases satiety. (Stomach distention may signal a sensation of fullness or satiety through the vagus nerve.) Increased bulk may also mean that the stomach takes more time to empty. Therefore, after meals rich in fiber, blood glucose and insulin levels are slower to rise. In some studies, half the variance of the glucose response to starchy foods depended on their fiber content.5

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

Soluble fiber reduces carbohydrate absorption, which in turn reduces blood glucose and insulin levels.

There are no long-term data on the use of vinegar for weight loss. However, smaller short-term human studies suggest that vinegar may help reduce insulin resistance.27 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.28 The addition of vinegar for sushi rice lowered the glycemic index of white rice by almost 40 percent.29 Addition of pickled vegetables and fermented soybeans (nattō) also significantly lowered the glycemic index of the rice. In a similar manner, rice with the substitution of pickled cucumber for fresh showed a decrease in its glycemic index by 35 percent.30

Type 2 diabetics drinking two tablespoons of apple cider vinegar diluted in water at bedtime reduced their fasting morning blood

Insulin can increase independently of blood sugar.

Rather than simply being a mechanism for food absorption and excretion, the gastrointestinal tract, with its nerve cells, receptors and hormones, functions almost like a “second brain.” The two human incretin hormones described so far are glucagon-like peptide 1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP). Both hormones are deactivated by the hormone dipeptidyl peptidase-4. The incretins are secreted by the stomach and small intestine in response to food. Both GLP-1 and GIP increase insulin release by the pancreas. Fats, amino acids and glucose all stimulate incretin release and thus, increase insulin levels. Even

Milk contains two main types of dairy protein: casein (80 percent) and whey (20 percent). Cheese contains mostly casein. Whey is the byproduct left over from the curds in cheese making. Bodybuilders frequently use whey protein supplements because it is high in branched-chain amino acids, felt to be important in muscle formation. Dairy protein, particularly whey, is responsible for raising insulin levels even higher than whole-wheat bread, due largely to the incretin effect.10 Whey protein supplementation increased GLP-1 by 298 percent.11

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.

But are dairy and meat fattening? That question is complicated. The incretin hormones have multiple effects, only one of which is to stimulate insulin. Incretins also have a major effect on satiety.

INCRETIN HORMONES PLAY an important role in the control of gastric emptying. The stomach normally holds food and mixes it with stomach acid before slowly discharging the contents. GLP-1 causes stomach emptying to significantly slow. Absorption of nutrients also slows, resulting in lower blood glucose and insulin levels. Furthermore, this effect creates a sensation of satiety that we experience as “being full.”

Eating fat does not make you fat, but may protect you against it. Eating fat together with other foods tends to decrease glucose and insulin spikes.32 If anything, dietary fat would be expected to protect against obesity.

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.

Eggplant, kale, spinach, carrots, broccoli, peas, Brussels sprouts, tomatoes, asparagus, bell peppers, zucchini, cauliflower, avocados, lettuce, beets, cucumbers, watercress, cabbage, among others, are all extremely healthy carbohydrate-containing foods.

Beans are a versatile, fiber-rich carbohydrate staple of many traditional diets. They are an extremely good source of protein, particularly for vegetarian diets. Edamame beans, popular in Japanese cuisine, provide 9 grams of fiber and 11 grams of protein per serving.