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 feelings of hunger and your desire to eat for a brief time.
- Calorie burning. Caffeine appears to increase energy use even when you're at rest. It stimulates thermogenesis — one way your body generates heat and energy from digesting food.
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.
The bottom line: Be cautious about using caffeine products to help with weight loss. When used in moderation (400 milligrams or less) by healthy adults, caffeine is generally safe. But too much caffeine might cause nervousness, insomnia, nausea, increased blood pressure and other problems.
Also keep in mind that some caffeinated beverages, such as specialty coffees, are high in calories and fat. So instead of losing weight, you might actually gain weight if you drink too many of these.