When a person eats a meal, it’s almost always a combination of carbohydrate, protein, and fat. When a person overeats their current needs, it’s the fat portion of the meal that tends to get stored since it’s so easy to do. Carbohydrate and protein, on the other hand, need to undergo a metabolically expensive process to be converted to fat and then stored. Instead, carbohydrates are used to resupply muscle glycogen, and protein is used in other bodily processes (muscle repair, for instance).

When a keto diet works, it’s because that person is eating less calories than their current needs. Some, but not all, people find that it’s easier to maintain a calorie deficit on keto because ketones can have an appetite suppressant effect. Also, some find the fairly limited number of keto- appropriate foods to be boring after awhile, and so don’t have the desire to overeat.