Here's the deal, dieters. You'll make great strides in your effort to lose weight if you get a little extra of this past your lips: water.

Upping your daily water intake by 33 ounces -- that's about 4 additional cups -- could help you melt an additional 2.5 pounds over the course of a yearlong diet. Here's the simple science behind the claim.

Water, Water Everywhere
When researchers evaluated the water-drinking habits of overweight women who were following various popular diets (from Ornish to Atkins), water intake helped tip the scales in the right direction. The women who either upped their water intake or replaced sweet drinks with water lost about an extra 2.5 pounds. But it had to be water: Switching to or adding diet drinks didn't have the same effect. (Read this article on the smart way to use sugar substitutes.)

Why Water's Great
So how does H2O give dieters an edge? It may be that drinking water helps reduce calorie intake -- you're full of water, so you eat less! It could also be that the agua alters your metabolism in some helpful way. Just keep in mind that drinking water, by itself, doesn't melt pounds. The women who benefited from the extra H2O were already on reduced-calorie eating plans. (Drinking water may be good for this, too.)

How much water do you need each day? This article can help you figure it out.