Eat how much are not fat may be due to personal exercise, gastrointestinal tract digestion problems or hyperthyroidism and other reasons. If their own exercise will greatly promote the body’s blood circulation, so that the body calorie consumption accelerated, burning fat, and thus less likely to make their own obesity. If the gastrointestinal digestive function is weak, and can not fully digest and absorb the food intake, because the body absorbs the calories and nutrients are not as much as the actual consumption, so it will not make weight gain. If you suffer from hyperthyroidism, the thyroid gland secretes more thyroid hormones, which puts your body in a high metabolic state and causes you to eat nothing but weight. At the same time, in addition to the above reasons, there may also be genetic factors that lead to such a situation. If accompanied by other discomforts, it is recommended to actively seek medical advice to find the cause.