"Alcohol interferes with the brain and kidney communication and causes excess excretion of fluids which can then lead to dehydration," he says.
2. Water Can Help Control Calories. For years, dieters have been drinking lots of water as a weight loss strategy. While water doesn't have any magical effect on weight loss, substituting it for higher calorie beverages can certainly help.
"What works with weight loss is if you choose water or a non-caloric beverage over a caloric beverage and/or eat a diet higher in water-rich foods that are healthier, more filling, and help you trim calorie intake," says Penn State researcher Barbara Rolls, PhD, author of The Volumetrics Weight Control Plan.
Food with high water content tends to look larger, its higher volume requires more chewing, and it is absorbed more slowly by the body, which helps you feel full. Water-rich foods include fruits, vegetables, broth-based soups, oatmeal, and beans.
3. Water Helps Energize Muscles. Cells that don't maintain their balance of fluids and electrolytes shrivel, which can result in muscle fatigue. "When muscle cells don't have adequate fluids, they don't work as well and performance can suffer," says Guest.
Drinking enough fluids is important when exercising. Follow the American College of Sports Medicine guidelines for fluid intake before and during physical activity. These guidelines recommend that people drink about 17 ounces of fluid about two hours before exercise. During exercise, they recommend that people start drinking fluids early, and drink them at regular intervals to replace fluids lost by sweating.
4. Water Helps Keep Skin Looking Good. Your skin contains plenty of water, and functions as a protective barrier to prevent excess fluid loss. But don't expect over-hydration to erase wrinkles or fine lines, says Atlanta dermatologist Kenneth Ellner, MD.
"Dehydration makes your skin look more dry and wrinkled, which can be improved with proper hydration," he says. "But once you are adequately hydrated, the kidneys take over and excrete excess fluids."
You can also help "lock" moisture into your skin by using moisturizer, which creates a physical barrier to keep moisture in.