Beyond its role in general health, water can make play a major role in maintaining body weight through a program of caloric restriction. Foods that contain large amounts of water, such as fruits and vegetables, have low energy density,and so may produce sensations
of satiety with low caloric intake.
Several published studies showed interesting patterns of food intake based on the water composition of foods. In one, subjects were given either food containing a high concentration of water, such as a soup of a stew, or the same solids prepared as a casserole, with
water to accompany the meal. Although in each case, the total amount of both solids and water were the same, subjects ingested fewer calories when the water was incorporated into the food source. In a related study, advising people to eat foods with low energy
density, that is, foods containing higher concentrations of water, was a more successful weight-loss strategy than attempts to limit portion size.
The second study evaluated the effects of preloading water before a meal. Subjects were asked to drink water before eating. Although subjects claimed that the quantity of water ingested had filled them up, and they had no appetite, the amount of food actually consumed after the pre-load was no different from that eaten by members of the control group. Although these studies are not definitive, they do indiate that foods with a high concentration of water, such as soups, stews, or salads, may be useful in weight loss programs by providing satiety with low levels of energy intake.