The various ketogenic diets that severely restrict all carbohydrates and replace them mostly with fats are associated with increased risk for non-alcoholic fatty liver disease or NAFLD (JAMA Intern Med, published online July 15, 2019). NAFLD can lead to diabetes, heart attacks, strokes, liver cancer and other cancers (Curr Opin Clin Nutr Metab Care, Jul 1, 2012;15(4):374-380). Ketogenic diets have also been associated with kidney stones, constipation, diarrhea, fatigue, headaches, bad breath, bone fractures, and an increase in LDL cholesterol that increases risk for heart disease. Ketogenic diets increase markers of cholesterol and inflammation, although they do lower triglycerides (Obesity, June 2019;27(6):971-981).
Any diet that restricts vegetables, fruits, whole grains and beans is unhealthful because these plant foods are rich sources of soluble fiber that is converted in your intestines to short chain fatty acids (SCFAs), which lower high cholesterol, high blood pressure, and high blood sugar. A deficiency of soluble fiber markedly increases risk for an overactive immune system (inflammation) that can damage cells throughout your body.
How Keto Diets Can Increase Risk for Fatty Liver (NAFLD)
Carbohydrates are made up of single and chains of sugars. The keto diet severely restricts all carbohydrates, so it does cause blood sugar levels to drop. This, in turn, also causes blood insulin levels to drop. This appears to be good because it causes fat cells to release their stored fat as triglycerides into the bloodstream. If a person on the keto diet then gains weight by any means, he is at increased risk for storing fat in his liver, rather than the much safer fat cells. The liver then pulls the fatty triglycerides from the bloodstream into its own cells, and if large amounts of triglycerides are stored in the liver, the person develops a fatty liver that can interfere with every beneficial function of the liver. Excess fat in the liver is a major cause of diabetes. When blood sugar levels rise, your pancreas releases insulin that lowers blood sugar by driving sugar from the bloodstream into the liver cells. If the liver is full of fat, the liver cannot accept sugar and blood sugar levels rise even higher to damage cells and cause diabetes.
More than 40 percent of North American adults have NAFLD, which has no symptoms or signs early on, so most people will not find out that they have this condition until they have already developed diabetes or suffered a heart attack. NAFLD is treated primarily with strict lifestyle changes as the FDA has not approved any drugs specifically for NAFLD.
How to Tell if You Have a Fatty Liver
If you have a big belly and small hips, you probably have a fatty liver and are already diabetic or pre-diabetic, even if your fasting blood sugar is below 100 (which is considered normal). If your blood sugar rises over 145 mg/dl one hour after meals, you are likely to have a fatty liver. Your doctor can order a simple, inexpensive sonogram of your liver which can show whether you have excess fat in your liver. Other indicators include abnormal liver function tests and high fasting insulin levels. A fatty liver is treated with every lifestyle treatment for diabetes including diet, exercise, and avoidance of alcohol.
Keto Diets Have Not Been Shown to Cause Permanent Weight Loss
Keto diets do restrict sugared drinks and sugar-added foods, processed foods, and other refined carbohydrates in bakery products, pastas and most dry breakfast cereals, foods that have been associated with weight gain, diabetes, heart attacks and premature death (Nutrients. 2017 May; 9(5): 517). However, I cannot find any long-term controlled studies showing that keto diets are associated with permanent weight loss. One supervised controlled study showed that the keto diet did not cause increased fat loss over other diets. Furthermore, the researchers were unable to show that it significantly increased the amount of energy the body burns (The American Journal of Clinical Nutrition, Aug 2016;104(2):324-333).
Keto diets are complicated to follow and are difficult for most people to stay on because of the very limited choice of foods. They:
• restrict many healthful foods, such as fruits, beans, whole grains, and vegetables, that have repeatedly been associated with reduction of disease
• usually include red and processed meats that have been associated with increased risk for heart attacks and some cancers
• increase intake of saturated fats that raise blood levels of LDL cholesterol, which has been associated with increased risk for heart attacks
• restrict vegetarians to extremely limited choices of foods such as avocados and coconut oils.
See Low-Carbohydrate Diets Can Harm
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I do not recommend ketogenic diets because:
• They usually involve restricting unrefined carbohydrates. There is a huge difference between unrefined and refined carbohydrates. Unrefined carbohydrates as are found in nature are almost always loaded with healthful soluble fiber and are associated with reduced risk for disease and increased life span. I do recommend restricting refined carbohydrates — sugared drinks and sugar-added foods, and other refined carbohydrates such as bakery products, pastas and most dry breakfast cereals.
• They encourage people to eat large amounts of red meats and processed meats, which I believe are unhealthful.
If you want to lose weight, I recommend Intermittent Fasting. To maintain a healthful weight, prevent disease and prolong your life, I recommend that you eat a wide variety of unrefined carbohydrates (vegetables, fruits, whole grains, beans, nuts and other seeds), and try to exercise every day.