Caffeine alone won't help you slim down. It may slightly boost weight-loss efforts or help prevent weight gain, but there's no solid evidence that caffeine consumption leads to noticeable weight loss.

Caffeine is found in many beverages, including coffee, tea, energy drinks and colas, and in products containing cocoa or chocolate. It's also found in 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 in animals, making the results questionable or hard to generalize to humans. Some studies found that 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 or teas, are high in calories and fat. Just adding milk and sugar to coffee or tea could set back your weight loss efforts, especially if you drink multiple cups a day. Instead of losing weight, you might actually gain weight if you drink too many of these higher calorie drinks.