"People who think they are going to buy an ‘ab machine’ and suddenly have a ‘washboard’ stomach are misinformed. If you want your abdominal (ab) muscles to appear, you will need to lose total body fat. Studies have shown that doing hundreds...thousands of sit-ups a day has no effect on body fat," says cardiologist James Rippe, MD. 

  Sit-ups can increase the size and power of your abdominal muscles but unless you lose excess body fat, you won’t see your abdominal muscles.... there is no such thing as spot reduction!

• When you lose body fat, you lose it from all areas of the body where it is stored.
• Muscle that’s built under fat will only push your abdominal fat farther out!
• If your stomach (i.e., abdomen) is too big, the best way to make it smaller is to eat a well-balanced diet and perform regular aerobic exercise (e.g., brisk walking, jogging, cycling, swimming, aerobics class) 30 - 45 minutes, 4-5 days per week.
• You should supplement your aerobic exercise with sit-ups and other strengthening exercises.

  Most of the models who promote the benefits of abdominal exercise on TV have between 6  and 10 percent body fat — which is a result of heredity, light eating and/or serious aerobic exercise.

  Men want to maintain an average of 12 - 20 percent body fat; women, 15 - 25 percent.