Only exercise the muscle strength of the upper body, that is, do anaerobic exercise. In this way, you only increase the muscle strength of the upper body, that is, do some restorative exercises or sit-ups or push-ups. These things can exercise your upper body, let you exercise your chest muscles and even your biceps, but if you don't run or squat, it won't affect your thigh muscles, and then naturally it won't affect your weight.