Fruits and vegetables, on average, contain about 80–90 percent water. Just as fiber can bulk up the volume of foods without adding calories, so can water. Experiments have shown that people tend to eat the same amount of food at a meal, regardless of calorie count—probably because stretch receptors in the stomach send signals to the brain after a certain volume of food has been ingested. When much of that volume is a zero-calorie component like fiber or water, that means you can eat more food but gain less weight.
