Contrary to popular opinion, you cannot produce localized spot reduction by performing a few sets of sit-ups every day. Only nutritional dieting and high activity training with minimum rest periods will cause weight loss. Heart and lung function are very important to emulsify fat.
Because they obtain the best blood supply in the body, the abdominals do not have to be worked with dozens of sets of high reps every day. Simply work the abs using 8-12 reps with 4-5 sets per exercise.