Situps can strengthen your abdominal muscles and even play a role in your goal of losing weight. However, burning a pound of fat requires more than just dedication to this exercise. The low calorie burn -- and the fact that you're unlikely to be able to perform more than a few sets of situps -- means that burning a pound of fat through this exercise alone is virtually impossible.
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Burning a pound of fat requires you to create a caloric deficit of 3,500 calories; in other words, you must burn this many calories more than you consume. The American Council on Exercise recommends combining diet and exercise as you work toward a caloric deficit. Burning 3,500 calories through situps alone requires you to perform an impossible number of reps. If a 145-pound person performs situps at a moderate pace of 20 per minute, she burns about 4 calories per minute. To burn 3,500 calories, this person would need to perform situps for 875 minutes -- and perform an unattainable total of 17,500 situps.