The main benefit of ketosis is that it increases the body’s ability to utilize fats for fuel, which gets very lazy on a high-carbohydrate diet. When on high-carbohydrate diets, the body can usually expect an energy source to keep entering the body. But in the state of ketosis, the body has to become efficient at mobilizing fats as energy.
Ketosis has a protein-sparing effect, assuming that you are consuming adequate quantities of protein and calories—0.7 grams per pound of body weight per day—in the first place.1 Once in ketosis, the body actually prefers ketones to glucose. Since the body has copious quantities of fat, this means there is no need to oxidize protein to generate glucose through gluconeogenesis.
Another benefit has to do with the low levels of insulin in the body, which causes greater lipolysis and free-glycerol release compared to a normal diet when insulin is around 80-120. Insulin has a lipolysis-blocking effect, which can inhibit the use of fatty acids as energy. Also, when insulin is brought to low levels, beneficial hormones are released in the body, such as growth hormone and other powerful growth factors.
Another small but very important benefit of the ketogenic diet is that when in the state of ketosis, ketones, along with a high protein intake, seem to suppress appetite.3 A high-carbohydrate diet, on the other hand, increases hunger levels. Because you have to consume a lot of fat on a ketogenic diet, which hold 9 calories per gram, you are not getting much food volume. It’s not mandatory to be hungry on a reduced-calorie diet.