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Chapter 8: Cortisol

Aug 09, 2019


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

You Will Learn

  • What is cortisol and why it is called the stress hormone.  
  • How do elevated levels of cortisol cause weight gain.  
  • What the research says about sleep deprivation and weight gain.  


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 8 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. 


What is Cortisol? 

Cortisol is a hormone made by your adrenal glands, a small triangle-shaped gland that sits on top of your kidneys.  

A synthetic version of cortisol is prednisone, an anti-inflammatory and immunosuppressive medication used in a variety of conditions like allergic disorders, skin conditions, ulcerative colitis, arthritis, lupus, psoriasis, or breathing disorders.

In Paleolithic times, cortisol played a very helpful role in times of “fight-or-flight” from an enemy or animal. When cortisol is released it causes the protein in your muscles to break down and be converted to glucose (blood sugar) so more energy could be readily available to be used by your muscles to fight or flee.  

When we had a stress, our cortisol levels went up, blood sugar was released to be used quickly by the muscles, and then cortisol levels would return to normal.  


Cushing’s Disease, Addison’s Disease, and New Onset Diabetes After Transplant

One of the most helpful ways to see the effects a hormone has on the body is to look at what happens if there is too much or too little.  

Cushing’s disease is characterized by a chronic overproduction of cortisol. The hallmark sign of Cushing’s disease is weight gain.  

Addison’s disease is the opposite. Addison’s is caused by insufficient functioning of the adrenal gland (where cortisol is made). It is characterized by low levels of cortisol and its hallmark sign is weight loss. 

Long-term use of prednisone (the synthetic form of cortisol) as part of their anti-rejection therapy in post-transplant patients leads to insulin resistance and can cause diabetes. This type of diabetes is termed “new onset diabetes after transplant” NODAT.  

In one study post-transplant patients who were slowly weaned from prednisone had a 25% drop in plasma insulin which translated to a 6% weight loss and 7.7 percent decrease waist circumference. I am not advocating for stopping your prednisone if you are on it after a transplant, just bringing this research and the link between cortisol and weight gain to your attention.  


How Chronic Stress Leads to Weight Gain - Cortisol and Insulin Resistance 

I like how Dr. Fung words it on page 93 when he says “stress contains neither calories nor carbohydrates, but can still lead to obesity. Long-term stress leads to long-term elevated cortisol levels, which leads to extra pounds.”  

Our bodies are well designed for short bursts of cortisol, especially when it is a physical stressor and we can put that extra available energy to use right away.  

Unlike Paleo times, our stressors look very different in today’s world. Work. Marriage. Kids. Bills. Heck even trying to lose weight can stress you out - talk about a double edged sword!  

When we are chronically stressed, our cortisol levels stay up. Cortisol causes more glucose to be formed and released into the bloodstream. Higher levels of glucose in the blood triggers insulin to be released to put the glucose either back into the liver or muscle cells in the form of glycogen, or if that storage is full the extra glucose is turned into fat.  

You can see the endless cycle that ultimately leads to something called insulin resistance. We will talk more about this in a later chapter.  

Insulin resistance is when your body gets so used to high levels of insulin, it becomes adapted and needs more and more to get the job done. More and more insulin leads to more fat creation and storage. High levels of cortisol have been shown to specifically increase abdominal obesity, an important indicator of overall health and risk of developing disease.  

For reference, a high risk waist circumference for developing type 2 diabetes and cardiovascular disease is 35 inches for women and 40 for men. 


Sleep Deprivation and Weight Gain 

We’ve all heard of it and probably experienced it...more or less anyway. The freshman fifteen. You finally fly the coup and a year later you weigh significantly more than you did when you left home. Why? It’s the perfect storm for weight gain. Most of the time people just blame the food and booze but in reality the food, alcohol, eating at crazy hours, stress, lack of sleep, and to a lesser extent lack of organized sports and physical activity. This environment is literally the perfect storm for weight gain.  

How about a new mom trying to get the weight off. If you are struggling with that I feel you, I know it’s hard, but it is worth it to the long-term health of yourself and your family to keep the effort going, even if it takes way longer than you wanted. If you are already eating well, try to get some support from a loved one for a real night of sleep, a massage, a haircut, coffee with a friend, a workout, something to help relieve the stress. Then make time in your calendar and do that on a regular basis. Reducing stress and sleeping has nothing to do with food but it will change the way your body is using it to better facilitate weight loss.  

How about the different set of stressors that come later in life. Night sweats from menopause, stress with kids, stress about your parents, and adult children waking you up and midnight to tell you their home (even if you're like my mom who didn't remember it in the morning), can cause disrupted sleep and interfere with your weight loss.  

I once worked with this wonderful nurse who said, “All you therapy people are lean and fit, and all of us nurses are so out of shape.”  

Let’s take a look at some of the research on page 94:  

“Research has shown a direct link between shift work and sleep deprivation and often report fewer than five hours of sleep per night. Population studies consistently link short sleep duration and excess weight, generally with seven hours being the point where weight gain starts. Sleeping five to six hours was associated with a more than 50 percent increased risk of weight gain. The more sleep deprivation, the more weight gained.”  

“A single night of sleep deprivation increases cortisol levels by more than 100 percent. By the next evening, cortisol is still 37 to 45 percent higher.”  

“Sleep deprivation is associated with higher body weight, decreased leptin (a hormone that tells you when you are full), and increased ghrelin (a hormone that tells you that you are hungry).” 

“Sleep deprivation under low-stress conditions does not decrease leptin or increase hunger, which suggests that it is not the sleep loss per se that is harmful, but the activation of the stress hormones and hunger mechanisms”.  


Bottom Line 

  • My approach to healthcare has four pillars: nutrition, exercise, sleep hygiene, and stress management. You need all for for optimal health. 
  • Chronically elevated cortisol levels increase your blood sugar, which increases your insulin levels, and leads to insulin resistance, the underlying mechanism for weight gain.
  • Good stress management and adequate, quality sleep are often overlooked during weight loss but they are essential to any weight loss and management program.  


1. Chapter 8. (2016). In J. Fung, The Obesity Code: Unlocking the Secrets of Weight Loss. Vancouver: Greystone Books. 

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