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Chapter 7: Insulin

Aug 02, 2019


Click here to watch a replay of the Facebook LIVE discussion.

You Will Learn:  

  • Research that proves a causal relationship between high insulin levels and obesity.  
  • Why some medications cause you to gain weight.  
  • How insulin is a central hormone in our body’s set-weight, meaning that lowering insulin, not calories, is needed for long-term weight loss and management.  


About Dr. Fung, Author of The Obesity Code and The Diabetes Code

Dr. Jason Fung is a medical doctor, nephrologist by trade, who specializes in kidney disease, type 2 diabetes, and obesity. He acknowledged that traditional medicine wastes time and resources attempting to treat symptoms of disease, rather than the cause of disease.  

You can purchase The Obesity Code book HERE. Most information in this post is direct from this book. 


Overview of the Book

Here is an outline of the book. Today I’m covering Chapter 7 in Part 3 of the book. 

  • Part 1: “The Epidemic,” explores the timeline of the obesity epidemic and the contribution of the patient’s family history. It highlights the underlying causes of obesity. 
  • Part 2: “The Calorie Deception,” reviews the current caloric theory in depth and highlights the shortcomings of the current understanding of obesity. 
  • Part 3: “A New Model of Obesity,” describes how hormones are involved in the development of obesity. These chapters explain the central role of insulin in regulating body weight and describe the vitally important role of insulin resistance. 
  • Part 4: “The Social Phenomenon of Obesity,” dives into childhood obesity and why obesity is associated with poverty. 
  • Part 5: “What’s Wrong with Our Diet?,” explores the role of fat, protein, and carbohydrates, the three macronutrients, in weight gain. In addition, it examines one of the main culprits in weight gain - fructose - and the effects of artificial sweeteners. 
  • Part 6: “The Solution,” provides guidelines for lasting treatment of obesity by addressing the hormonal imbalance of high blood insulin through proper nutrition, sleep, and stress management. 


Brief Overview of How Different Macronutrients Affect Insulin Levels 

If you have been watching these videos and reading my content, I hope you know how different types of food affect how much insulin is released. There are three types of macronutrients: carbohydrates (these include starches, sugars, and fiber), proteins, and fat.  

Refined sugars and starches found in table sugar, high fructose corn syrup, and refined grains like cereal and flour cause the biggest insulin release. That is because they are refined to the point where there is no fiber, protein, or fat to slow it down. Blood sugar spikes and so does insulin to ensure your blood sugar doesn’t get too high. Think of insulin as the key that lets sugar into your body’s cells.  

Protein causes a low blood sugar response but a modest insulin response, and fat causes almost no blood sugar or insulin response. Check out this article for more information on the different types of carbohydrates and how they can affect insulin.  

The picture in this article is a helpful visual reminder for how different macronutrients will affect insulin. Most foods are a combination of these 3 macronutrients. For example, a chicken breast is mostly protein, and egg has some protein and fat, raspberries are a carbohydrate with some sugar and fiber. Avocado contains fiber, fat, and protein. Pop just contains sugar. Juice is only sugar.  

It’s a lot easier to make healthy food choices when you switch your mindset to start thinking of food in this way rather than counting points or calories.  


Research Proves High Insulin (Not Excess Calories) Causes Obesity 

High insulin has long been associated with obesity. Obese individuals have 20% higher fasting levels of insulin and it takes longer for their insulin levels to come down to baseline after eating. These elevated levels of insulin are strongly correlated with waist circumference and waist/hip ratio.

Research has also shown a close association between obesity and high fasting insulin measured after an overnight fast. This association is even stronger when just looking at high insulin levels related to fat mass, not total body weight.  

But just because there is an association doesn’t always mean that is the cause. The next section discusses research that proves high insulin does in fact cause obesity.  

As Dr. Fung describes, the “insulin causes obesity” hypothesis is easily tested. If you take insulin, will you get fat? The answer is a resounding YES! In addition, there is a direct dose-response relationship, the more insulin to take the more weight you gain.  

I won’t get into all the research Dr. Fung does in the book but one study I thought was particularly interesting was done in 1993 where over time a diabetic client’s insulin was increased over a period of 6 months to 100 units a day to keep their blood sugars tightly regulated and avoid the damaging effects to the eyes, kidneys, and nerves of high blood sugar. 

At the same time, they reduced their calorie intake by 300 per day. The results? The patient’s blood sugar was great but they gained 19 pounds in 6 months. Despite eating fewer calories, they had a significant weight gain because of the increased insulin.  

Another example is of research done on people who have a rare tumor that constantly secretes insulin, called an insulinoma. The high insulin levels would cause recurrent episodes of hypoglycemia (low blood sugar). But 72% of the patients with this tumor reported weight gain. Removal of the tumor resulted in rapid and sustained weight loss.  


Medications and Weight Gain

As I mentioned above, insulin that is injected causes weight gain. The more insulin that is injected, the more weight the patient gained.  

But there are several other medications, usually taken by patients with Type 2 Diabetes to lower their blood sugar, that can cause weight gain, depending as you will see on their mechanism of action.  

I won’t get into the mechanics of how these medications affect insulin levels as Dr. Fung describes this in the book. He gives several different diabetes medication examples and explains their mechanism of action. Some increased insulin levels and some blocked the digestion and absorption of glucose. Those that didn’t increase insulin didn’t cause weight gain. Those that did increase insulin did cause weight gain. 

Other medications have also been known to cause weight gain. The examples Dr. Fung gave in his book were olanzapine, gabapentin, and quetiapine. Other common examples are birth control pills, blood pressure lowering medications like metoprolol, and antidepressant medications like sertraline.  

I can’t tell you how many times I would see older adults who were on many of these medications all at the same time. It’s a double-edged sword to have to take medications for high blood pressure and diabetes that increase insulin resistance and cause weight gain, when insulin resistance and excess weight likely caused the high blood pressure and diabetes in the first place! The power of preventative medicine becomes more evident all the time.  

For me, this is really where the excess calorie theory breaks down. If something is correct it should be correct in every circumstance but how insulin levels increase or decrease in response to a medical condition or with medications, and how this directly impacts weight gain or loss, independent of caloric intake, hammers the point home that obesity is caused by an excess of insulin, not excess calories.  

On page 86 Dr. Fung summarizes this point nicely. “The results are very consistent. Drugs that raise insulin levels cause weight gain. Drugs that have no effect on insulin levels are weight neutral. Drugs that lower insulin levels cause weight loss...a recent study suggests that 75 percent of the weight loss response in obesity is predicted by insulin levels. Not willpower. Not caloric intake. Not peer support or peer pressure. Not exercise. Just Insulin." 


Insulin's Role in Your Body Set Weight 

"Insulin causes obesity - which means that insulin must be one of the major controllers of the body set weight. As insulin goes up, the body set weight goes up. The hypothalamus sends out hormonal signals to the body to gain weight. We become hungry and eat. If we deliberately restricted caloric intake, then our total energy expenditure will decrease. The result is still the same - weight gain.”  

Common sense would tell us that body fat regulation is not that special of a process that it deserves a completely different mechanism to control. We don’t consciously control our body set weight anymore than we control our heart rate, breathing rate, how fast our hair grows, or our body temperature. These are all automatically regulated by our body's hormones and so is our body set weight. Hormones tell us when we are hungry, full, how much energy (calories) to burn, and how much fat to store.  

Hormones are the ultimate or underlying cause of obesity, calories are just the proximate or apparent cause. When you focus all your energy on only the apparent cause of a problem you can waste a tremendous amount of time, energy and money.  

If insulin is the main ultimate cause of obesity, logic drives me to ask a follow-up question, how?  

This is a much more complex problem that researchers are still working on. There are several theories out there, one being the link between insulin and leptin, the hormone that tells you that you’re full. I won’t get into that here but you can read this theory on page 87 in The Obesity Code.  

As Dr. Fung summarizes on page 88, “the crucial point to understand is not how insulin causes obesity, but that insulin does, in fact, cause obesity. Once we understand that obesity is a hormonal imbalance, we can begin to treat it. If we believe that excess calories cause obesity, then treatment focuses on reducing calories. But this method has been a complete failure. However, if too much insulin causes obesity, then it becomes clear we need to lower insulin levels. The question is not how to balance calories; the question is how to balance our hormones. The most crucial question in obesity is how to reduce insulin.” 


Bottom Line 

Excess insulin, not excess calories, is the underlying cause of obesity and long-term treatment should focus on helping clients lower insulin levels.  



1. Chapter 7. (2016). In J. Fung, The Obesity Code: Unlocking the Secrets of Weight Loss. Vancouver: Greystone Books. 

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