Where does weight go when you lose it?

Your body is a machine, of course a very special machine. But like other machines, it needs energy to keep it working. It gets the energy by burning the foodstuffs that you eat to make carbon dioxide and water. Your largest amount of weight loss is in the carbon dioxide you breathe out.

Your weight really doesn’t change much from day to day. So the gains and losses are pretty closely balanced. Your income of food and water is balanced by your losses in urine, feces, and the carbon dioxide and water breathed out of your lungs.

One way to tell about the loss of carbon dioxide and water that you breathe out is to weigh yourself carefully when you go to bed and again when you wake up. If you have a good bathroom scale, you may be able to tell that you lose almost a pound during the night.