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Chapter 15 | The Diet Soda Delusion

Sep 12, 2019


Check out a replay of the Facebook LIVE discussion for this Chapter HERE.  

You Will Learn

  • How artificial sweeteners don’t help you lose weight. 
  • Harmful potential side effects of artificial sweeteners. 
  • Suggestions for how to overcome your diet pop addiction. 


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.


Overview of the Book

Here is the outline of the book. This post covers chapter 15 in Part 5. 

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. 


Artificial Sweeteners DON’T Help You Lose Weight 

The long-standing theory that obesity is caused by too many calories in, and not enough calories out, prompted the creation of a myriad of artificial sweeteners. The main source of these in the standard American diet is diet pop or other diet drinks like sports drinks, some flavored waters, and teas. Other commonplaces we find artificial sweeteners are granola or protein bars, cereals, ice cream, and yogurts. 

If you subscribe to that theory of obesity, logic would follow that diet drinks with fewer calories and less sugar would lead to weight loss. But the scientific evidence does not support this. 


Artificial Sweeteners Raise Insulin Levels 

Evidence shows that short-term weight loss is affected by how many calories you consume, but your long-term weight loss is determined by your body set weight, which is in large part controlled by your insulin levels. The entire Obesity Code book discusses obesity as a problem of too much insulin, not too many calories. If we want to lose weight, we need to lower insulin. 

The problem with artificial sweeteners, and why they don’t actually lead to weight loss, is because they raise insulin levels. Dr. Fung states on page 172 that “despite having a minimal effect on blood sugars, both aspartame and stevia raised insulin levels higher even than table sugar...artificial sweeteners may decrease calories and sugar, but not insulin.”


How Can Artificial Sweeteners Raise Insulin if They Don’t Contain Calories

If you have been following my stuff for a while, you likely understand by now that insulin is a hormone that is released by your pancreas in response to the food we eat, especially carbohydrates. 

Carbohydrates, specifically starches and sugars, are broken down into glucose (blood sugar). Insulin acts as a key to move this glucose from our bloodstream into our cells for energy or to be stored as fat. 

But if artificial sweeteners contain no calories or carbohydrates, how can they raise our insulin levels? One potential answer is the Cephalic Phase Insulin Response. This is when your brain triggers insulin to be released in the first few minutes of a meal, even before your blood sugar goes up. In essence, your body is preparing for the rush of blood sugar by having insulin readily available to move the glucose into your cells. (Dhillon et al) ***Cephalic simply means “head”.


Artificial Sweeteners Increase Food Cravings and Overconsumption of Sweet Foods

Many of my clients tell me they just want to eat sugar all the time. They have intense food cravings. They may be trying to drink diet pop or other diet drinks to reduce those cravings but unfortunately they are making things worse. 

When you have something sweet without the calories, your brain thinks it is getting calories and this triggers and incomplete sense of reward. Your brain hates open loops. Why do you think movie trailers or the end of one TV episode always leaves you guessing. Producers know that your brain hates open loops and you will come back for next week’s episode. Your brain is like that when you eat artificial sweeteners, you leave the loop open and it will trigger you to want to eat something with calories to close that reward loop. 

On page 172, Dr. Fung states that “most controlled trials show that there is no reduction in caloric intake with the use of artificial sweeteners.” You may be saving the calories from the regular pop, but your brain will likely make you eat something later to make up for it. Next time you drink something sweet but sugar-free, notice how your body will start craving more sweet food. 


What Health Risks are Associated with Artificial Sweeteners?

According to Ruiz-Ojeda et al, consumption of artificial sweeteners might actually contribute to:

  • Obesity
  • Type 2 Diabetes
  • Cardiovascular Disease
  • Increased Appetite
  • Risk for Some Cancers

Dr. Fung points out on page 171 at least ten studies in the Obesity Code verifying his opinion that artificial sweeteners are bad for your health. Here are just a few: 

  • The Women’s Health Initiative Observational Study found a 30 percent increased risk of cardiovascular events (heart attacks and strokes) in those drinking two or more diet drinks daily. 
  • The Framingham Heart Study showed a 50 percent higher incidence of metabolic syndrome in diet soda users. Metabolic syndrome includes high blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol levels. The syndrome increases a person's risk for heart attack and stroke.
  • The San Antonio Heart Study studied over 5,000 women over eight years and found that instead of reducing obesity, diet beverages substantially increased the risk by 47 percent. 


Bottom Line

  1. Excess weight comes from your body set weight being too high from too much insulin in your system for too long, not too many calories. While artificial sweeteners contain no carbohydrates or calories, they do increase your insulin levels and create an incomplete reward loop in your brain, causing you to crave more sweets. 
  2. Long-term studies on the effects artificial sweeteners, specifically diet pop, has on our health have shown an increased risk of obesity, type 2 diabetes, and cardiovascular events like strokes and heart attacks. 
  3. If you are struggling to stop drinking pop, I believe diet pop can be a good stepping stone but you should not stop there. I’d love to see you continue to work towards other, healthier alternatives like Bubly or La Croix sparkling waters if you are looking for the carbonation, or tea if you need a hit of caffeine. If you think you are addicted, that may be true, but you got yourself there and you can get yourself out. The only way to change a bad habit is to replace it with a better one. This takes time, patience, persistence, and consistency but you can do it!
  4. If you like to use artificial sweeteners for cooking to reduce your sugar intake, just know they are not better for you than regular sugar and should be consumed like regular sugar - in moderation and preferably just on special occasions. 



  1. Chapter 15. (2016). In J. Fung, The Obesity Code: Unlocking the Secrets of Weight Loss. Vancouver: Greystone Books. 
  2. Dhillon J, Lee JY, Mattes RD. The cephalic phase insulin response to nutritive and low-calorie sweeteners in solid and beverage form. Physiol Behav. 2017;181:100–109. doi:10.1016/j.physbeh.2017.09.009.
  3. Ruiz-Ojeda FJ, Plaza-Díaz J, Sáez-Lara MJ, Gil A. Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials. Adv Nutr. 2019;10(suppl_1):S31–S48. doi:10.1093/advances/nmy037.

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