Drink Water to Lose Weight First of all, water has no calories, is fat-free and cholesterol-free, and is low in sodium. Second, it is an appetite suppressant. Third, water helps the body to metabolize stored fat. How? Well, when the kidneys do not have enough water, they cannot function properly. The liver steps in as a backup, but doing so hinders its ability to metabolize fat effectively. The fat thus remains stored in the body, and you gain weight.