— Answers from Katherine Zeratsky, R.D., L.D.
Caffeine may slightly boost weight loss or prevent weight gain, but there's no sound evidence that increased caffeine consumption results in significant or permanent weight loss.
Caffeine is found in many beverages, including coffee, tea, energy drinks and colas; in products containing cocoa or chocolate; and in a variety of medications and dietary supplements, including supplements aimed at weight loss.
Although research about the connection between caffeine and weight isn't definitive, there are a few theories about how caffeine might affect weight, including:
Appetite Suppression - Caffeine may reduce your desire to eat for a brief time, but there's not enough evidence to show that long-term consumption aids weight loss.
Calorie Burning - Caffeine may stimulate thermogenesis – one way your body generates heat and energy from digesting food. But this probably isn't enough to produce significant weight loss.
Some studies looking at caffeine and weight were poor quality or done on animals, making the results questionable or hard to generalize to humans. In addition, some studies found that even decaffeinated coffee may contribute to modest weight loss, suggesting that substances or factors besides caffeine may play a role in weight loss.