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The Obesity Code Summary – Dr. Jason Fung

Lillian Teague
by Lillian Teague
Lifelong learner. Stephens Alum. Writer at TAoL.
The Obesity Code (2016)
Unlocking the Secrets of Weight Loss
TAoL Rating: Book Rating: 5/5 5.0

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One-Sentence Summary

The Obesity Code gives an amazing look at how the body uses food to create the perfect conditions for obesity and how to disrupt the cycle to create a healthier future - by kidney disease specialist, best-selling author and MD, Jason Fung. (328 pages)

Note: This The Obesity Code summary is part of an ongoing project to summarise the Best Health Books of all time.

The Obesity Code Review

Today’s medical world revolves around treatment, not prevention.

But what if we flipped that around?

The Obesity Code: Unlocking the Secrets of Weight Loss by Dr. Jason Fung came into my life while I was trying to kick my sugar habit for health reasons.

But while I expected just-another-diet-book filled with “do this” and “don’t eat that,” what I found was a pleasant surprise.

Dr. Fung doesn’t just talk about numbers on scales.

He has a bigger point to make…

To prevent obesity you must first understand it.

The Obesity Code teaches the science behind what causes obesity in a way anyone can benefit from and understand – no matter your age, health, or weight. It goes beyond the basic details of dieting and will inspire you to master your health.

While I will always have a sweet tooth, this book definitely helped me refocus on my health priorities. I treat my cravings with healthier options and avoid added sugars far more often.

The result? A healthier me for the long term.

Learn how you can get there too in this book summary of The Obesity Code…

The Obesity Code Summary

Dr. Jason Fung is a physician from Toronto who specializes in kidney disease.

How does kidney disease tie into obesity?

Frustrated at simply treating patients, Dr. Fung began looking for a way to prevent kidney disease.

What he found was a common link between type 2 diabetes and our kidneys.

His conclusion? To prevent kidney disease, prevent type 2 diabetes.

But what he found was that traditional diabetes management wasn’t working. Traditional “healthy diets” weren’t working.

It’s partly because we’re bombarded with conflicting information.

Eat this… No, don’t eat that… Oh, it’s okay to eat that. Nope, it’s bad again.

No wonder we all feel confused.

But it’s also because even doctors don’t know about and aren’t offering advice that’s based on good research and data.

Dr. Fung has spent over 20 years helping type 2 diabetics lose weight and reverse their diabetes. And he’s created a simple, time-tested step-by-step process for losing weight, preventing weight gain, and maintaining a healthy life through diet.

This summary of The Obesity Code follows the six parts of Dr. Fung’s book:

  1. The Epidemic;
  2. The Calorie Deception;
  3. A New Model of Obesity;
  4. The Social Phenomenon of Obesity;
  5. What’s Wrong with Our Diet? and
  6. The Solution.

Click on a link above to jump ahead or read on below…

The Epidemic

What is obesity?

Obesity is being overweight to the point of having negative health consequences. In order to reverse the negative effects, you have to lose weight.

Most doctors and dieticians will tell you that the key to weight loss is to simply eat fewer calories while burning more calories.

Calories come from the food we eat. They are units of energy calculated by burning foods in a lab and measuring the amount of heat released.

The history of counting calories began in the early 1900s with a series of bestsellers that indicated calories were what led to weight gain. If you want to lose weight, experts said, cut your calories.

Dr. Fung doesn’t agree with calorie focussed diets (caloric diets) because they tell people the only reason they can’t lose weight is that they eat too much and are lazy.

The truth? That isn’t the case.

During the late 1970’s, calories got a pass because there was a new dietary enemy in town: fat. Declared to be the cause of heart disease and obesity, fat was the new thing to avoid.

A low-fat, high-carb diet soon became the trend. The basis of the food pyramid became breads, pastas, and potatoes. A high-carb diet was the healthy solution for many decades.

But as Dr. Fung points, calories and fat are not the cause of weight gain. Your hormones control weight gain. (It’s one reason women are more likely to transform excess calories into fat.)

However, it turns out the types of food you eat can make your hormones act in peculiar ways (And – spoiler alert! – blood-sugar-spiking carbohydrates are the enemy!).

What’s more, because hormones are in control, there’s a genetic link to your propensity to gain weight. In fact, as much as seventy percent of how your hormones affect your weight gain comes from your parents.

Your hormones control how your body fat is regulated. They control how much fat you store, where it grows, and how your body uses it in the future.

Conclusion? There’s more to weight management than just calorie counting.

We’ve been living in the shadow of…

The Calorie Deception

Dr. Fung lays out 5 false assumptions about calories:

  1. ❌ You can cut calories in AND increase calories out. The assumption says that you can reduce your incoming calories while increasing your outgoing calories through exercise. However, calorie-deficit diets aren’t sustainable. While you may see some initial weight loss, long-term changes will be minimal. If you cut incoming calories, you eventually have to cut the calories you are burning.
  2. ❌ Your metabolic rate is steady. The belief that you burn a certain amount of calories on a regular basis doesn’t take into account all of the variables that make up your metabolism. In fact, Dr. Fung points out that your total baseline energy expenditure can go up and down 50% when everything is factored in.
  3. ❌ We can control calorie storage. Because we take time to eat, we assume that we are in control of our eating. However, our bodies are really the driving factor in when we eat and how much we eat. Just like breathing, body-fat regulation is automatic. We don’t have to think about it.
  4. Fat growth just happens. Actually, nothing in our bodies just happens. Everything is controlled by hormones. From our growth to our fat cells, there are hormones interfering in every single body system.
  5. A calorie is just a calorie. That’s actually not the case. Not all calories are the same. Proteins, fats, and carbs all contain calories, but the body uses these foods in very different ways. Each one stimulates different hormones.

A New Model of Obesity

So, if calories aren’t to blame, what is?

Answer: Hormonal imbalance.

Hormones are the molecules that deliver messages to cells. For example, insulin tells human cells to take glucose out of the blood and use it for energy.

In order to deliver a message, a hormone must first attach to a target cell by binding to receptors on the cell surface. Think of it like a shuttle docking with the space station.

Insulin, it turns out, isn’t just important for regulating blood sugar. High insulin levels encourage fat storage, while low insulin levels lead to fat burning. If insulin levels are high for an extended period of time, the body responds by storing as much fat as possible.

In fact, Dr. Fung claims that insulin is so powerful that he can make you gain weight as easily as prescribing you insulin. It doesn’t matter what you eat or how many times you hit the gym, too much insulin over too long makes you obese.

Numerous studies have backed this fact up. Doctors know that insulin causes weight gain. When insulin levels go up, people gain weight. It doesn’t matter if the insulin is injected, increased with medication, elevated by high cortisol levels, or through food choices, high insulin levels over a long period of time cause the body to store fat.

And what happens if insulin levels are reduced?

Your body stops the process and you lose weight.

The Social Phenomenon of Obesity

In addition to our basic biology, there are powerful added social factors that make it hard for many folks to lose weight.

Reality? It is almost impossible to go through an entire day without being influenced by the food industry. The options out there are endless, and so is the messaging.

It all comes down to money.

How can your food choices be monetized by big companies and corporations?

Very easily, it turns out.

Dr. Fung discusses three myths perpetrated by the food industry:

  1. Snacking is good for your health;
  2. Breakfast is the most important meal of the day; and
  3. Adding fruits and vegetables to your diet makes it healthy.

Each of these myths is a lie, according to Dr. Fung.

Each was designed to sell products and not to help you get healthier.

In addition to advertising, Dr. Fung points out the well-established tie between socioeconomic status and obesity. States with the highest levels of poverty also have the highest levels of obesity.

Just check out these graphs of poverty vs. obesity, sedentariness and diabetes in US counties grouped by wealth…

The Obesity Code Summary: Poverty vs Obesity in the USA


This is because the cheapest and most filling foods are often refined carbohydrates, such as pasta and bread. These foods are cheap because of agricultural subsidies for corn and wheat growers.

And as we’ll see shortly, it’s these foods that have the worst impact on insulin and obesity.

Result? State-sponsored obesity that targets the poorest and most vulnerable in society.

What’s Wrong with Our Diet?

So what’s the secret assassin in our diets? Carbohydrates.

Carbohydrates drive up blood-sugar which in turn drives up insulin levels. Over time, high insulin levels lead to increased fat storage and weight gain.

What carbs are the worst offenders?

Dr. Fung points to sugar as the most fattening of all carbs.

Sugar is made of glucose and fructose.

Glucose drives up blood sugar fast, forcing the body to churn out more insulin which helps get the sugar into cells and into storage.

Fructose has a different effect. Our cells don’t like fructose. They can’t use it. While insulin is moving glucose into cells, fructose goes straight to the liver. The liver breaks it down and stores excess fructose as fat.

Fatty liver leads to insulin resistance. Insulin resistance causes the body to produce higher levels of insulin. And this causes even more storage of fat in the liver and more insulin resistance.

While your liver is fighting for its life, you are gaining weight.

Conclusion? If you only make one change to your diet, stop eating sugar.

Cut out sugar and you’ll bring down your insulin levels.

Bring down insulin and you’ll start losing weight.

Note: Don’t be fooled into thinking you can remove sugar and replace it with substitutes. Studies show that chemical sweeteners, like those in diet sodas, do nothing to decrease insulin because those fake sugars simply increase your overall cravings for (and consumption) of real sweets.

So what about other carbs?

The easiest way to break carbs down into good carbs and bad carbs is to look at the glycemic index. When a carb has a high glycemic index and glycemic load score, it has a faster impact on your blood sugar, which drives up insulin.

High glycemic foods include white bread, processed cereals, soft drinks and candy.

Low glycemic index foods, like vegetables and some fruits, still contain carbohydrates, but those carbs take a bit longer to digest so they don’t have the same impact on your insulin levels.

Here’s a chart to help you visualise where some common foods sit…

The Obesity Code Summary: Glycemic Index Chart

The Solution

Dr. Fung starts off his solution by reminding us that:

  • All diets work; and
  • All diets fail.

Why do all diets fail?

For weight loss to become permanent, two things must happen. First, you have to lose weight until you reach your body set weight – the preset “fat thermostat” controlled by your brain.

To do so, Dr. Fung suggests the following steps:

  1. Step 1: Reduce added sugars.
  2. Step 2: Reduce simple carbs and highly processed grains.
  3. Step 3: Make protein 20 to 30 percent of your total calories.
  4. Step 4: Eat more natural fats.
  5. Step 5: Increase beneficial foods, such as fiber and vinegar.

But that’s only part one.

Because the trouble, thanks to long-term insulin resistance, is that your initial body set weight is often still too high to be healthy. And your body has several mechanisms in place to make sure losing more weight than that becomes challenging.

So the second thing you need to do, to keep these steps working for the long-term, is work on reprogramming your insulin resistance.

The easiest way to do this is to lower your insulin through fasting.

It may not sound fun, but there are many different ways to successfully fast. You can fast for 24 hours, fast for 16 hours (usually overnight and in the early morning) or simply reduce calories for a few days a week.

Dr. Fung includes sample meal plans and fasting protocols at the end of his book. He answers questions such as:

  • What do I do if I get hungry while fasting? Keep going–it will pass.
  • Can I exercise? Yes.
  • Will I get tired, confused, or forgetful? No.
  • My stomach is growling. What do I do? Drink some water.

In addition to diet breakdowns and fasting techniques, Dr. Fung includes some key ideas to reducing stress levels naturally. Stress leads to the production of cortisol, a hormone that influences insulin production.

How can you reduce stress? Get enough sleep. Meditate. Relax. Breathe. Take time to focus on yourself and your body.

The Obesity Code FAQs

What Are the Main Points of the Obesity Code?

The main points of The Obesity Code are:

  1. What you know about weight loss is wrong – Eating less and exercising more doesn’t work. Dr. Fung reveals that the cause of obesity is hormonal. All you need to do is manage your hormones to manage your weight and health.
  2. Obesity is a sign of hormonal imbalance – Hormones govern many of the processes in our bodies, including our weight. A simple hormone imbalance can cause an insulin and leptin cycle that leads to obesity.
  3. When you eat is as important as what you eat – To end the cycle of insulin and leptin resistance, Dr. Fung recommends intermittent fasting and foods that regulate your blood glucose levels.

For a full breakdown, check out this FREE summary of the book.

What Diet Does Jason Fung Recommend?

The diet Dr. Jason Fung recommends is made up of two main takeaways: when to eat and how to eat.

Eating at the right time can help end the hormone resistant cycle that causes unhealthy weight gain. Intermittent fasting is the method of fasting from food for a period of time.

It may sound hard, but there are several different versions of intermittent fasting. You can fast for an entire day or just portions of the day. You can also choose to simply restrict calories a few times a week. You can customize fasting to best fit your lifestyle with meal timing around your schedule. The goal is to simply go for extended periods of time without eating.

In addition to fasting, Dr. Fung recommends avoiding foods that cause insulin resistance. He recommends cutting way back on added sugars, processed foods, and simple carbs. You should also increase your consumption of fats, fiber, and vinegar. Think of it as a low-carb, mid-protein diet full of healthy fats and fiber.

What Are the Causes of Obesity?

The causes of obesity include:

  • Society influences our eating decisions through advertisements;
  • Doctors don’t understand the science of weight gain; and
  • The mixed messages we receive and not knowing what or who to trust.

However, Dr. Fung says it all still comes down to the fact that obesity is caused by our hormones. When insulin reaches a high level for an extended period of time, fat storage and weight gain is the result. A cycle of insulin resistance increases insulin levels and the problem compounds into obesity.

The biggest factor behind elevated insulin levels is simple carbohydrates, especially added sugars. When combined with stress and increased cortisol levels, simple carbs create a fast path to obesity.

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