MYTH
I have often heard that you should sweat as you are excercising. So I was wondering, does the actual act of sweating cause you to burn more calories? Or is it just a way to measure how hard you are working?
The fact is that sweating itself does not burn any calories, such as sitting in a sauna. This merely makes you perspire, but not burn fat. The exercises you do when you sweat are which burn calories, but the sweat itself has nothing to do with it.
The sweating is merely a process of homeostasis, your body reacting to and attempting to keep the body cool when either you are in a hot environment (e.g. the sauna) or are being active both will cause a rise in a body temperature.
We should remember that the loss of weight through excess sweating as experienced in the sauna/steam room is not fat but water. Such weight returns immediately you consume fluid. Consequently if you lose say two and a half pounds in a session in the steam bath you will replace it with approximately the next two pints of water drunk (one pint of water weighs a pound and a quarter).
However and obviously more worrying is that if the fluid loss is replaced by a high calorie drink you may end up gaining fats because of your weight loss attempt.