"People who think they're going to buy a 'ab machine' and suddenly have a washboard stomach are misinformed," says cardiologist James Rippe, MD.

If you want ab muscles to appear, you'll need to lose total body fat. Studies have shown that doing thousands of sit-ups a day has no effect on body fat. Sit-ups can increase the size and power of your abdominal muscles, but you won't see your abdominal muscles unless you lose excess body fat.

Some facts from the doctor:

• Muscle that's built under fat will only push your fat farther out.
• You can't spot reduce. When you lose fat, you lose it from all areas of your body where it is stored.
• Aerobic Exercise is the fastest way to burn fat.
• If your abdomen is too big, the best way to make it smaller is to restrict calories and to get regular aerobic exercise. Sit-ups and other strengthening exercises should supplement your aerobic program.