How Much Weight Will You Lose if You Drink Water for a Week?

Water not only keeps you hydrated and mentally focused, it provides several nonpharmaceutical methods for supporting your weight-loss efforts. Drink water for fasting or as a calorie cutter or appetite suppressant. This inexpensive, sugar-free, calorie-free beverage can move you more quickly toward your weight-loss goal, but it's not a sure thing.

A young woman drinking a bottle of water outside. (Image: DAJ/amana images/Getty Images)

Beverage Replacement

Drink water as a replacement for sugar-sweetened beverages. Sugary sodas, juices, smoothies and sports drinks can contain 200 or more calories in a 12-ounce serving. If you replace one sugary beverage a day with water, you consume up to 1,400 fewer calories a week, for a weight loss of about 1/2 pound. In one month, you consume 6,000 fewer calories. By the end of one year, replacing just one sugary drink a day with water can cut 73,000 calories from your diet for a potential weight loss of 21 pounds -- without dieting. Unsweetened drinks such as seltzer, regular coffee, tea and diet soda count as water. Add a little flavor to your water with a slice of lemon, orange, lime, fresh fruit or mint leaves.

Appetite Suppressant

Drink water as an appetite suppressant before eating. It gives you the sensation of fullness, which helps you eat less. Water before meals can potentially increase your weight loss by about 1/2 pound per week. The February 2010 issue of “Obesity” published the first randomized, controlled clinical trial to determine the effect on weight loss when dieters drink water before meals. The 12-week study included 48 dieters, 55 to 75 years of age. Half of the dieters drank 2 cups of water before each low-calorie meal; the second half ate the same low-calorie meal but did not drink water prior to eating. At the end of the 12-week trial, the water drinkers lost 15.5 pounds, while the nonwater drinkers lost 11 pounds. The additional 5 pounds lost by the water drinkers equals 1/2 pound weekly weight loss.

Water Fast Risks

To lose 1 pound of body fat, you must cut out 3,500 calories. If you routinely eat a 2,000-calorie diet and consume nothing but water for one week, you might potentially lose 4 pounds. However, drastically reducing calorie intake triggers starvation mode and muscle wasting, which slows your metabolism so you burn fewer calories. Health risks associated with prolonged water fasts include possible brain damage, anemia, organ damage, electrolyte imbalance and low blood pressure, according to Texas A&M University. Without a lifestyle change, fasting alone does not promote permanent weight loss. When the fast ends, if you return to your regular eating habits, you quickly regain the lost pounds. A successful weight-loss regimen must include a healthy diet and regular exercise.

Water Fast Benefits

On the positive side, studies conducted at the Intermountain Medical Center showed stress caused by hunger elevates cholesterol levels, forcing the body to burn fat for fuel. In a 2011 study at IMC, levels of human growth hormone, also called HGH, increased in subjects participating in a 24-hour water fast. HGH increases and protects lean body mass and promotes fat breakdown. A reduction in body fat decreases the risk of diabetes and heart disease. However, the researchers state the need for more studies before they can recommend fasting. Talk to your doctor if you're considering a fast.