Thermal suits, also known as sauna suits, are shiny body wraps that promote sweating. They're most commonly used by boxers, wrestlers and others who need to cut a significant amount of weight in a short time. They do promote weight loss, but not the kind most people are seeking. Thermal suits cut water weight, which does not make you any healthier. In fact, it can make you very ill.
For years, the only people who wore thermal suits were boxers and wrestlers. This is with good reason--they compete in sports driven by weight class and may need to drop a few pounds quickly to qualify for a match. They can use sauna suits safely because they're already in great shape and usually do so under a trainer's professional supervision.
How They Work
Thermal suits trap your body's heat. This in itself will cause sweating (think of sleeping under a very warm blanket.) But coupled with exercise, the sweat glands will start working overtime. The more you sweat, the more water weight you lose.
Why They Won't Work For You
Most often, people who want to lose weight are dissatisfied with the way they look: their belly is too big, their arms look fat or they have a double chin. This weight isn't sweat--it's fat. The only way to burn fat is to lose it through diet, cardiovascular exercise and weight training.
Also, as soon as you stop wearing the thermal suit and replace all the water you've sweated out, you will gain back any weight you lost.
Why They Can Be Dangerous
Sweat's role during exercise is to evaporate, cool the body and prevent heat exhaustion. Thermal suits don't allow sweat to evaporate, leaving the wearer at risk of overheating. Also, heavy sweating causes dehydration, which in turn makes you tired. Dehydration also can cause vomiting and diarrhea. Severe cases of dehydration can result in shock, seizures, brain damage and death.