The ketogenic diet is very low in carbohydrates: in its strictest form, carbs make up only five percent of daily calories, along with 20 percent from protein and 75 percent from fat. Some versions of the diet allow a little more protein (about 35 percent of calories) while others alternate five high-fat days with two high-carb days. The object of the emphasis on fat is to bring about ketosis, the metabolic state of burning fat instead of carbohydrates for energy. There’s little doubt that you can lose weight this way, although there is no scientific consensus on how this occurs. Some researchers contend that weight loss on this diet is a simple matter of consuming fewer calories, while others propose an appetite-suppressant effect of ketosis.
Whatever the mechanism, a number of studies have concluded that you can lose more weight faster on a ketogenic diet than on a low-fat diet. However, you may have to contend with negative side effects of ketosis, such as headache, fatigue, constipation, increased cholesterol level, and bad breath – although these are usually temporary. If you have kidney disease, the diet isn’t for you; it can worsen this condition
Some history: The ketogenic diet has been used at least since the 1920s as a treatment for young children with severe epileptic seizures that are difficult to control with medication. We don’t know why inducing ketosis decreases the frequency of seizures, but it often does. It seems to work best for kids ages one to 10.
More recently, some studies have found that ketogenic diets may have value for treatment of other health problems. In a 2013 review published in the European Journal of Clinical Nutrition, an international team of researchers wrote that there is “ample evidence to support the notion that a low-carbohydrate diet can lead to an improvement in some metabolic pathways and have beneficial health effects.” They cited research showing that a ketogenic diet can have favorable effects on risk factors for cardiovascular disease including elevated cholesterol and triglyceride levels. Other studies have found that a ketogenic diet can help individuals with metabolic syndrome, insulin resistance and type 2 diabetes by improving glucose control and insulin sensitivity. The review also cited “persuasive, although not yet conclusive” evidence that it can reduce the severity and progression of acne. They also maintained that the ketogenic diet shows promise “as an aid in at least some kinds of cancer therapy and is deserving of further and deeper investigation.” The review also suggested that it might be useful in the treatment of polycystic ovary syndrome (PCOS), Alzheimer’s disease, Parkinson’s disease, and amyotrophic lateral sclerosis (ALS).
Andrew Weil, M.D.
Antonio Paoli et al, “Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets.” European Journal of Clinical Nutrition, August 2013, doi: 10.1038/ejcn.2013.116