Contrary to what celebrities may say, waist trimmers won't help you lose belly fat, won't cause you to lose weight, or give you liposuction-like results. All a waist trimmer can do is temporarily tighten your torso and give the illusion of a slimmer figure. Women often wear compression garments, such as corsets and girdles, to achieve this effect. Waist reducer belts work in the same way, wrapping and compressing the stomach to make you look thinner.
The Mayo Clinic states that using a girdle-like device can improve your appearance and posture, but it won't strengthen or tone stomach muscles. The only way to truly flatten your stomach is through diet and exercise. Trimmer straps are basically elastic girdles that you can wear before workouts to trap heat. Manufacturers claim that heat increases body temperature, leading to better weight loss results.
These abdominal belts are usually made from neoprene, a synthetic rubber. They come off inches from the waist and may reduce your waist circumference by 1 to 2 inches. However, this weight loss is not permanent. You may be able to temporarily reduce your waist circumference with an abdominal belt, but there is no research to support its ability to help you lose weight in the long term.