Sweat Suits
Wrestlers, boxing, mma fighters and other athletes who needs to come in below a given weight, will often attempt to shed water weight if they are above their weight limit. Water makes up 45 - 75 percent of the bodies weight and is the easiest weight to lose in the short term.
Sweat suits are often not much more and moisture than non-breathing vinyl which trap body heat and moisture. Sweat is expelled by the body because as it evaporates, it cools the body down. By trapping the moisture, a sweat suit minimizes the cooling effect. The body increases its sweat output in an attempt to increase cooling. Higher end models such as the realsauna ultimate sweat suit look better - far better than most actually, but beneath the more respectable and affluent looking exterior is a plastic lining which traps the heat and moisture.
In the short term, sweating works. When you drink you replenish those fluids - and your body needs those fluids. Over any real time horizon, I don’t see how a sweat suit leads directly to fat or even weight loss.