The Obesity Code – Unlocking the Secrets of Weight Loss 

In The Obesity Code, Jason Fung argues that for decades, we’ve misunderstood obesity and, as a result, have consistently failed in our efforts to curb its spread. To solve this epidemic, he asserts that we need a new, comprehensive theory of obesity.

Fung presents this theory, arguing that obesity is a hormonal problem that causes overeating and weight gain, rather than a problem of willpower or self-control. He contends that overcoming it involves improving your diet and fasting regularly.

Fung is a Canadian nephrologist (kidney specialist) and head of the Intensive Dietary Management Program in Toronto. After witnessing diabetes patients gain weight from insulin treatment, he began to explore type 2 diabetes and obesity, two conditions that often lead to kidney disease.

The Obesity Code, published in 2016, received positive reviews and has been called one of the most comprehensive treatments of obesity yet written. Today, Fung is recognised as an expert on fasting and obesity. He continued his investigative medical writing in The Diabetes Code (2018) and The Cancer Code (2020).

How we misunderstand obesity and weight-loss

Mistaken Premise #1: “All Calories Are the Same”
Traditionally, experts have reduced all foods to calories, or units of food energy, and treated calories as the most important aspect of any food. However, Fung asserts that not all calories are the same. For instance, 100 calories of high-fructose corn syrup is quite different from 100 calories of salmon. Research supports this view, showing that different foods cause different metabolic and hormonal reactions in the body. Because obesity is a hormonal disease, this means that various foods have different impacts on obesity.

Mistaken Premise #2: “Calories In and Calories Out Function Independently”
These variables in fact depend on each other. Your metabolism adapts to your caloric intake: When you eat less, your metabolism slows down to conserve energy. When you eat more, it temporarily speeds up, having more energy to burn. In other words, you can’t reduce calories in without slowing calories out, and you can’t increase calories out without increasing calories in. So “eat less, move more” can’t work, because you need to eat more in order to move more, and vice versa.

Mistaken Premise #3: “Exercise Contributes to Weight Loss”
The notion that exercise leads to weight loss is a core tenet of the prevailing theory—it’s the “calories out” part. However, Fung asserts that we’ve misunderstood how the body uses energy: Exercise accounts for a percentage of total energy expenditure, but most energy goes to our “basal metabolic rate,” which includes beating our hearts and powering our brains.
Considering these other activities, exercise accounts for only around 5% of energy expenditure, so it’s too small to make a meaningful impact on weight loss. In addition, studies show that:

– The modern-day office worker expends about the same amount of calories as a modern-day hunter-gatherer tribesman who walks 15 to 20 miles a day.
– One massive study of over 50,000 overweight women found that controlling diet and exercise had no significant effect on weight loss. In contrast, some participants gained weight.
– Statistically, rates of exercise and obesity have risen in tandem—suggesting that exercise doesn’t effectively combat weight gain.

Mistaken Premise #4: “The Individual Controls Her Eating”
Fung explains that eating isn’t a conscious choice—rather, our hormones control when we feel hungry or full.

Mistaken Premise #5: “Unused Calories Go Directly to Fat Storage”
Here, Fung explains that it’s a mistake to assume that all unused calories go directly to fat storage. That is, the belief that fat storage works like a waterskin—the more you add without removing any, the larger it gets. However, research shows that various hormones such as leptin and adiponectin mediate fat storage. What this means, Fung argues, is that whether you store excess calories as fat depends on your hormones, not on whether you burn enough energy. Therefore, obesity must be a hormonal problem, not a calorie problem.

Obesity is a Hormonal Issue

In short, Fung contends that obesity results from a hormonal dysfunction that centres on chronically high insulin levels. Chronically high insulin throws your body’s fat storage out of balance, disrupts your hunger hormones, and drives intractable weight gain. Here’s how:

Fat Storage Depends on Your Set Weight
Fat storage, Fung explains, hinges on the interaction between insulin and your “set weight.” Simply put, normal insulin levels stimulate your body to store a fixed amount of fat, depending on how small or large you are. That default amount of fat is called your set weight, and your body constantly works to maintain it.

If you fall beneath your set weight, your body will store calories as fat in order to reach it. If you go above your set weight, your body will increase your metabolism to burn off fat and reach it. This works similarly to cruise control in a car. Set at 55 mph, you can brake or accelerate but, when left alone, the car will always return to 55 mph.

Fung explains set weight as a homeostatic mechanism. Homeostasis, which refers to self-regulating bodily processes that maintain balance within an organism, is the central concept of physiology. Normal homeostasis produces good health, and disrupted homeostasis leads to disease. Fung’s theory appears to be consistent with this principle.

This effectively compels you to overeat in order to store fat until you reach the weight your body “thinks” it should be at. Thus, Fung argues, obesity isn’t caused by overeating—overeating is caused by obesity. The term “obesity” refers to the hormonal problem, and the resulting fatness is the main symptom.

If we take Fung’s above assertion as true, then our common perception that “obesity = being fat” is wrong. Further, the notion that obesity means being fat likely contributes to the stigmatisation of obese people. If, on the other hand, we accept that fatness and overeating are symptoms of an underlying disease, public perception of obesity could change.

As an analogy, consider if we shamed cancer patients for being sickly. Doing so seems absurd—those conditions result from the cancer, so there’s no reason to stigmatise them.

How the body processes foods

Fung explains that when you eat, your body breaks down the three main macronutrients—carbohydrates, fats, and proteins—into their constituent parts. Respectively, these are glucose (a basic sugar), fatty acids, and amino acids. Avoid confusing these with micronutrients, a category composed of vitamins (organic molecules made by plants and animals) and minerals (inorganic compounds that can’t be broken down). The body needs both for healthy function, and many micronutrients participate in the metabolic processes Fung describes. (He goes much more in to detail after this)

Poor diet and frequent eating unbalance this system

Fung explains that this system falls out of balance when we eat the wrong foods and when we eat too frequently. Both of these activities increase insulin levels. High and persistent insulin levels cause insulin resistance, a condition wherein the body needs more insulin per cell to successfully deliver glucose for energy.

Diet Composition—What You Eat

The first main factor that contributes to chronically high insulin levels is your diet’s composition, or what you eat. According to Fung, processed carbohydrates—specifically wheat and added sugars—contribute heavily to obesity. They cause insulin to spike sharply upward, and they promote overeating despite lacking nutritional value. Added sugars also cause fatty liver and insulin resistance, further contributing to obesity.

Processed Carbs

Highly refined carbs are starchy sugars that have been stripped of any fibre, fat, protein, and micronutrients that you’d find in the whole food. (White wheat flour is the prime example.) Because they’ve been processed into a fine powder, the digestive system rapidly absorbs them. This rapid absorption causes a sharp spike in blood glucose levels, which in turn spikes insulin levels. These spikes underlie the development of chronically high insulin levels. Foods such as white bread, snack cakes, crackers, chips, and pastries all have this effect.

The Danger of Added Sugars

In addition to the problems found in all processed carbs, Fung explains that added sugars, such as table sugar and high fructose corn syrup, will severely damage your health.

Meat and Dairy Also Stimulate Insulin

While refined carbohydrates are the main concern, in fact, all foods raise insulin levels. This occurs because of two hormonal mechanisms: the incretin effect and the cephalic phase effect. Put simply, your body releases insulin in anticipation of eating as well as when food reaches your stomach. Proteins stimulate far more insulin release than dietary fats, and vegetable proteins stimulate far less insulin release than meat and dairy. Given this, Fung says that we need to consider the meat and dairy that we eat.

Meat: Meat is generally associated with weight gain. One study he cites found that for each additional daily serving of meat, subjects gained one additional pound. Fung speculates that this may be due to the industrial production of meats—that is, animals fed with corn and grains, rather than their natural diets, produce meats that are less healthy for consumption.

Note: Grain-fed beef, for example, does have a higher proportion of saturated fat than grass-fed beef. Additionally, factory-farmed meats are often treated with antibiotics and drugs—in effect, eating grain-fed beef means eating the meat of an unnaturally obese cow. Some believe that this is intuitively unwise, though the science is still out.

Dairy: In contrast to meat, research finds that dairy products such as whole milk and cheese do not cause weight gain. In fact, large studies found that some dairy products, such as yogurt, may even promote weight loss. Fung suggests that this is because dairy is very filling: While you could eat a pound of chicken, you’d be hard-pressed to eat a pound of cheddar (although I give it a good go sometimes).

Bad Fats and Good Fats

According to recent research, there’s little relationship between obesity and the amount of dietary fat you consume. Studies have found that saturated fats, long thought to cause heart disease, may actually have a protective effect on obesity since they’re highly satiating. In addition, Fung advises avoiding refined vegetable oils, such as canola, soy, and corn, as well as trans fats, such as margarine. Each has been linked, respectively, to inflammation and heart disease.

Meal Timing—When You Eat

The second main factor that contributes to chronically high insulin levels is meal timing, or when you eat. Fung explains that chronically high insulin doesn’t result from insulin-spiking foods alone—it also requires constant insulin stimulation. When insulin levels are both high and constant, your body’s cells become insulin resistant. That kicks off the self-perpetuating loop of chronically high insulin that drives obesity.

Constant insulin release occurs when we eat too frequently.

Insulin levels increase in response to food, and they decrease between periods of eating. If you leave little or no time between periods of eating, you never allow your insulin to return to normal levels. The more frequently you eat, the faster you’ll create insulin resistance in your body.

Snacking: According to Fung, snacks have little or no nutritional value and no place in a healthy diet. Snacks are often made of refined carbohydrates, such as wheat and sugar, so they spike your insulin levels and contribute to obesity. Fung suggests that “Big Food” companies created snacks to generate more profit, and that they’ve disrupted the traditional “three square meals” eating pattern that allowed insulin to drop between meals.

Breakfast: Much like snacks, Fung contends that breakfast foods are unhealthy and contribute to obesity. Like snacks, many breakfast foods are made of cheap, processed carbs, and “Big Food” pushes the notion that “breakfast is the most important meal of the day” in order to profit from unaware consumers. Research shows that breakfast is inessential to good health, and Fung recommends skipping it or replacing carb- and sugar-heavy breakfast foods with whole, unprocessed foods such as salmon or a salad.

The Effects of Chronic Stress

In addition to what and when you eat, Fung explains that chronic stress contributes to weight gain. When you’re under stress, your body releases cortisol. Cortisol temporarily raises blood glucose levels, which triggers the release of insulin. Chronic stress causes constant cortisol release, which causes constantly elevated blood glucose, which in turn causes increased insulin levels. And as we’ve explained, chronically high insulin drives obesity.

Given this, Fung argues that chronic stressors, such as sleep deprivation and work-related psychological stress, contribute to obesity. To offset these stressors, Fung recommends practicing active stress reduction. Get at least eight hours of sleep nightly, since research shows that missing even a few hours increases insulin resistance and contributes to weight gain. You can also try practicing mindfulness meditation, yoga, or other mind-body activities that lower stress levels.

How to Overcome Obesity

Now that we’ve described Fung’s theory of obesity, let’s look at how he recommends overcoming it. In short, beating obesity means changing what you eat as well as when you eat—mirroring the argument that diet composition and meal timing contribute to high insulin, thus causing obesity.
In practice, this means eating a healthy diet composed of whole foods and engaging in regular, 24- to 36-hour fasts. Whole foods help you feel full and don’t spike your insulin, while regular fasting lowers your insulin levels long enough to reverse insulin resistance. When insulin resistance reverses, your set weight will drop and your body will adjust by burning off fat until you reach that weight.

Change What You Eat

Fung outlines several diet changes that reduce your insulin levels and combat obesity. In general, a healthy diet involves a high amount of healthy fats, a moderate amount of healthy proteins, and a moderate amount of healthy carbohydrates.

Change #1: Avoid added sugars. Forgo sugar-sweetened drinks such as soda, refrain from snacking on sugary snacks and avoid sugary breakfast foods. Feel free to enjoy quality desserts, like bakery-made cakes and cookies, on special occasions, but not every day.
The alternatives: Instead of consuming sugar, choose unsweetened drinks and foods. Snack on nuts and fruits in moderation, and choose unsweetened coffee, tea, or water. For breakfast, choose healthy foods such as a vegetable omelette. For dessert, enjoy a square of dark chocolate with cacao content over 70%.

Change #2: Avoid refined carbohydrates, primarily wheat. Flour-based foods spike insulin levels and drive obesity. By removing them from your diet, you increase your chance of beating this disease. According to Fung, refined wheat products have no place in a healthy diet. While whole wheat retains some protein and fat, it’s still a highly refined powder that will spike insulin.
The alternatives: Instead of consuming refined carbs, choose whole carbs and eat them in moderation. This means many vegetables—such as tomatoes, broccoli, and zucchini—and healthy seeds and grains. In particular, Fung recommends quinoa, chia, and beans, all of which contain carbohydrates, fibre, protein, and various micronutrients.

Change #3: Choose healthy proteins and fats. Fung recommends eating 20% to 30% of your diet as protein. In his view, high protein diets are difficult to follow, since isolated protein is difficult to find in whole food forms and forces you to rely on artificial substitutes, such as protein powder. Choose grass-fed meats, wild-caught seafood, and whole, vegetable proteins. For fats, choose unprocessed fats including olive and coconut oils, natural lards, and fatty foods like avocados. Healthy fats stimulate insulin the least and may protect against obesity.

Change #4: Eat foods that suppress insulin spikes. Some foods, such as those high in fibre, can offset the insulin stimulation caused by carbohydrates and proteins. Fung recommends consuming whole, fibrous foods such as fruits and berries, seeds, and whole oatmeal. In addition, vinegar and fermented foods, such as kimchi, reduce insulin spikes and help you feel fuller. While fermented foods are known for their health benefits, they aren’t free of downsides. For instance, kimchi can potentially develop harmful bacteria and has been linked to outbreaks of E. coli. In addition, it has high sodium content that may not be appropriate for everyone.

Change When You Eat

Fung argues that intermittent fasting is the key to beating obesity. Combined with a healthy diet, intermittent fasting heals insulin resistance—here’s how it works.
In the short term, most diets produce weight loss. However, dieting alone can’t fix obesity, because dieting doesn’t lower your set weight. Once you fall beneath that set weight, your body will compel you to eat and regain any lost weight. To lower your set weight, Fung recommends intermittent fasting. Intermittent fasting is an eating pattern wherein you intentionally stop eating for a stretch of time. Research has shown that regular fasting reduces insulin resistance, lowering your set weight and allowing you to lose fat steadily.

According to Fung, fasting is a time-honoured practice that humans have used to maintain good health for thousands of years. During our hunter-gatherer past, food was periodically scarce. To handle this, our bodies adapted to store fat as a backup energy source in times of need. Since then, physicians in ancient cultures, such as ancient Greece, have lauded fasting as a powerful cure for many illnesses. Many religions prescribe fasting as a regular “purification” practice, and over three billion Muslims, Christians, and Buddhists fast as a normal part of life.

While some worry that fasting is unhealthy, Fung explains that these concerns are misplaced. He argues that fasting does not cause your body to consume your muscles for fuel, damage your metabolism, deplete your blood sugar, or deprive you of essential nutrients. In contrast, studies show that fasting regulates blood sugar and electrolytes, produces an increase in human growth hormone that conserves your muscles, and increases your metabolism once ketosis kicks in. For these reasons, Fung asserts that anyone can fast successfully and reap powerful health benefits.

I hope you have found this summary useful. As always, there is a huge lack of context here as I’ve skipped so much to keep it brief-ish. Here is the link for the book [https://amzn.to/3EQqW0p] (https://amzn.to/3EQqW0p)

October 18th, 2022. Andrew Horide, Osteopath