Do ab belts really work?

A study published in the Journal of Sports Science and Medicine studied 41 individuals and found that after using an abdominal belt 5 days a week for 2 months, the participants did not lose any body fat but did experience significant gains in abdominal muscle strength.

Gains in abdominal muscle strength do not generally produce a difference in the body's appearance. Most people's abdominal muscles are not readily visible, and the only way to produce a flat, defined stomach is to remove body fat through diet and exercise. If used in addition to diet and exercise, an abdominal belt may be helpful in producing a toned, defined midsection.