A few studies indicate that large amounts of caffeine may slightly enhance weight loss in people who exercise and maintain a low-fat diet. This may seem encouraging. But read on.

Caffeine is a stimulant that can make your heart beat faster, increase your blood pressure, interrupt sleep and cause nervousness and irritability.

Studies have used amounts of caffeine equal to six cups of strong coffee a day. But even this amount doesn't seem to greatly increase the body's ability to burn calories (metabolic rate). It also doesn't result in significant loss of body fat.

Caffeine can suppress appetite. Some people assume that if they use caffeine, they'll eat fewer calories. But the appetite-suppressant effect of caffeine doesn't last long enough to lead to significant weight loss.

Caffeine is a diuretic, which acts to help your body lose water by increasing the amount of urine. This water loss may decrease body weight, but the weight you lose isn't body fat.

At first glance, it may seem that caffeine is a weight-loss aid. But it's not. No studies indicate that weight loss from large amounts of caffeine is significant or permanent. Also, many caffeinated beverages contain sugar, which adds calories and contributes to weight gain.