Because for people with poor physique, exercise not only consumes fat, but also strengthens the function of internal organs and increases the proportion of muscles in the body composition. But the proportion of muscle is larger than that of water, and the proportion of fat is smaller than that of water. If a dieter loses 1kg of fat but increases 1kg of protein, it is bound to gain weight. This situation is most obvious in the early stage of exercise. When the metabolic rate returns to a higher level, the dieter's ability to decompose fat will be enhanced, and then he will see a slow but sustained weight loss.