How many sit-ups do you have to do for your waist size to lose two inches?

The number of sit-ups that you need to do to lose two inches depends on many factors. The first is how much you weigh when you begin. The second is how long it takes to do those sit-ups. The faster you do them, the more calories you burn. Doing 100 sit-ups in 10 minutes will burn approximately 57 calories.