Dry eating is divided into pathological and physiological reasons, physiological for genetic and physical factors, pathological for hyperthyroidism and poor spleen and stomach digestive function, as follows: 1, physical factors, due to genetic factors, some people have a body that is not easy to fat, even if the amount of food, exercise less will not gain weight. And some people are easy to fat body, even after dieting to lose weight, slightly increase the amount of food will also appear obese phenomenon. 2, hyperthyroidism, excessive secretion of thyroid hormones, the human body to the intake of protein, fat, sugar metabolism accelerated, so there will be too much to eat but hungry fast, but the body wasted, limbs weak. 3, the spleen and stomach digestive function is not good, patients suffering from stomach disease spleen and stomach digestive function is not good. Eat into the food can not be digested and absorbed in time, in the overeating will appear the symptoms of diarrhea.