When you exercise, your body gets ramped up: heart-rate goes up, sweat starts to pour, muscles start working, lungs fill with oxygen and you get out of breath, etc. Your body needs fuel to make all that happen.

We’ve all seen them. Two-piece “sauna suits” made of nylon or vinyl that promise if you wear them, you’ll lose weight. I’ve even seen folks cut arm holes into plastic garbage bags and wear them to jog or workout in.