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Dr. Sears' Blog

Breaking down the latest research on Anti-Inflammatory Nutrition
Written By: Dr. Barry Sears, Ph. D | Creator of the Zone Diet

Written by Dr. Barry Sears
on September 04, 2019

Chances are you or someone you know has tried the keto diet. This high-fat, very low carbohydrate eating plan is enticing for many because of its promise for quick weight loss. We had the opportunity to ask Dr. Sears some questions about the keto diet and get his thoughts on the plan. See why he says the cons far outweigh the pros and why you may want to think twice before jumping on this trend.

Question: What is the Ketogenic Diet?  

Answer: The keto diet is a high fat, very low carbohydrate diet. This reduction in carbohydrates puts your body into a metabolic state called ketosis. This only occurs when there is not enough stored glycogen in your liver to convert fatty acids completely to carbon dioxide and water (i.e. a clean burn). In ketosis, the fatty acids are not completely burned to make ATP, so you make less energy. Contrary to popular belief, ketones are not a good source of energy for the brain as glucose remains the preferred fuel source for ATP production in the brain. 

Question: What do you consider the pros and cons of this eating plan?

Answer:  With this eating plan the cons greatly outweigh the pros.


  • Rapid initial weight loss in three days is primarily due to loss of retained water, but not stored body fat. So, if you are thinking only about weight loss, this could be considered a pro.
  • Less thinking by removing carbs from the diet. 
  • Less hunger by eating more protein.
  • Acetone is one of the ketone bodies produced during ketosis. Acetone is also the primary chemical in nail polish.
  • A ketogenic diet increases calcium loss from bones.
  • High levels of dietary fat on a ketogenic diet will reduce the likelihood of using stored body fat for energy unless you have significant calorie restriction at the same time. 
  • Lack of ATP production on a ketogenic diet makes it easier to become fatigued with mild exercise. 
  • After seven days on a keto diet, eating a single “cheat meal” (one high in carbohydrates) causes damage to the blood vessels.   
  • Lack of polyphenols on a ketogenic diet makes it difficult to activate the genes required to optimize your metabolism by improving the efficiency of the mitochondria in converting fat into chemical energy (ATP). 
  • There is no difference in weight loss on a ketogenic diet compared to a low-fat, high-carb diet in long-term studies. 
  • Careful studies have demonstrated there is no "metabolic advantage" on a ketogenic diet and that the fat loss on the ketogenic diet is the same as a low-fat, high-carb diet with the same number of calories in the short-term.  
  • Lack of fermentable fiber due to lack of carbohydrates leads to compromised gut health and increased likelihood of developing a leaky gut (condition in which bacteria and toxins can "leak" through the intestinal wall), which can become a significant source of inflammation. 
  • Build-up of cortisol levels to convert muscle mass to glucose for the brain which is the preferred fuel source for the brain.  Excess cortisol increases insulin resistance which makes you regain the lost weight body as fat, depresses the immune system making you more likely to get sick, and destroys memory cells in the hippocampus. 

Question: A main component of the diet involves your body going into “Ketosis”. How does this happen?  

Answer: To completely metabolize fat to carbon dioxide and water, you need to have a sufficient level of carbohydrates in the liver stored as glycogen.  The liver glycogen is also the primary storage site for glucose that can be used to replenish blood sugar levels to maintain adequate glucose for the brain.  If the carbohydrate levels are too low in the liver, the incoming fat is not completely metabolized and because of this incomplete fat burning metabolic products known as ketones begin to appear in the blood.  These are recognized as foreign and the body increases urination to remove them. That's why ketogenic diets deliver early weight loss but primarily in the form of dehydration.    

Question: Do people see real benefits or is this just another fad?    

Answer: A true ketogenic diet is also a calorie-restricted diet since it is difficult to consume high levels of fat without carbohydrate. Calorie restriction itself will have benefits by lowering the levels of inflammation, but only if protein, fat, and carbohydrates are relatively balanced as shown in highly controlled clinical studies. In fact, those studies indicate that a ketogenic diet is a pro-inflammatory diet.

Question: Would the keto diet make you gain weight?

Answer: There is no such thing as a “metabolic advantage” to a ketogenic  diet. Fat loss is simply a matter of calorie reduction.  A ketogenic diet reduces the minimum blood glucose levels needed for brain function so much that the body is forced to increase the secretion of cortisol which breaks down muscle mass into glucose for maintaining brain function. As cortisol levels build up, this causes an increase in insulin resistance resulting in elevated insulin levels which causes weight to regain. This problem is more apparent in females than in males.  

Question: How does the keto diet impact gut health?

Answer: Gut health requires both fermentable fiber and polyphenols coming from vegetables, fruits, and whole grains. A ketogenic diet will likely be deficient in both. In addition, saturated fatty acids (especially palmitic acid) found in ketogenic diets enable the transport of microbial fragments into the blood which will increase inflammation. A ketogenic diet is usually rich in saturated fats, especially palmitic acid which is the most pro-inflammatory saturated fat.

Fermentable fiber is the source of nutrition for the bacteria in the gut and without adequate levels, the bacteria will start digesting the mucus barrier that is your first line of protection against a leaky gut. Polyphenols disrupt the biofilms used by pathogenic bacteria to evade detection and destruction by the gut's immune system. Anything that disrupts gut health is a leading cause of microbial-induced inflammation. There is nothing magical about a keto diet and careful studies have demonstrated it offers no metabolic advantage. It works for weight loss because it is also a calorie-restricted diet.New call-to-action


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