The caffeine in coffee raises basal metabolic rate (BMR), the rate the resting body burns calories. As BMR increases, fat decreases, and the body sheds unwanted pounds. In medically supervised weight-loss programs, those who supplement a low-calorie diet and regular exercise with caffeine lose a little more weight. Not much, but enough to include caffeine in some weight-loss programs. However, caffeine only helps those who are severely obese, weighing well over 20 percent more than their recommended weight. It does not help those with more modest weight-loss goals—5 to 10 pounds.
Coffee and tea contain caffeine and may cause jitters, irritability, insomnia, and addiction.