You'll find that if you are under weight that it would bring you up in weight. It is good for establishing the best weight for your body without excessively adding more fat (in the form of triglycerides) to your body. This is because you are not eating carbohydrates that turn into directly into triglycerides, putting fat where you don't want it. i.e on your stomach and back. The main benefit of keto diets would be on your digestive systems and can solve a lot of ulcserative, heliobactor and acidity related issues.