That is a good question. I know it has to do with less fat stored in the cells, so it's harder to come off. Also, if your already at a healthy weight range for your age, sex, height and body type, it can be hard to get off. Keep plugging along. Kick up your exercise program. Upping intensity burns more calories and fat! Up your protein and high fiber intake! Up your exercise duration or try something new. You can do it!