Exercise to lose weight instead of weight gain may be due to insufficient exercise, excessive calorie intake after exercise, increased muscle mass in the body and other reasons. 1. Not enough exercise: exercise is a way to lose weight, if the exercise is not enough strength, intensity, time, then the consumption of calories is not enough, will also lead to weight gain. 2. Excessive calorie intake: not only do you need to exercise when you lose weight, but you also need to control your calorie intake. When too much calorie intake after exercise, it will increase glycogen in the body, and the excess glycogen can be converted into fat, thus making weight gain. 3. Increased muscle mass in the body: exercise leads to an increase in muscle mass in the body, muscle density is greater than fat, therefore, exercise to lose weight will be the phenomenon of weight gain. Weight loss is a long-term process, the weight loss process should gradually increase the amount of exercise to prevent the phenomenon of muscle strain, to pay attention to persistence. More knowledge about weight loss exercise, you can consult a professional doctor.