Caffeine is an appetite suppressant but this effect does not last for very long — not long enough to lead to significant weight loss. Does caffeine increase your body's ability to burn calories? Maybe, but again, probably not to show any significant weight loss.

Caffeine is a diuretic, which means the drug causes an increase in the amount of urine you excrete. This water loss may decrease your body weight. But it does not decrease body fat. Also, you should be aware that caffeine is a stimulant that can increase your blood pressure and heart rate, interrupt your sleep, and cause irritability and nervousness. Many caffeine based drinks are high in calories, which can contribute to unwanted weight gain.

Recent studies also indicate that caffeine raises both insulin and blood sugar levels. This leads to temporary signs of a condition called insulin resistance. As well as making weight loss more difficult, some experts believe that insulin resistance increases can your risk of both type II diabetes and heart disease.