Because the metabolic system, more effective weight loss for those who are and will be able to help keep weight stable weight is increased (to eat, rather than using, but if being obese ate less than they make skinny)
Because the system is to burn more efficiently. And for those who are weight, it can help make constant weight. The weight did not increase (It used to be more than fat, but if you eat less, used to make thin).
Because determining metabolism system more efficient. And for those watching their weight on it can help make weight, weight increase (eat more than use will make you fat. But if you eat less.