Caffeine may boost metabolism and promote fat loss, but these effects are likely to remain small over the long term.
Because of its ability to stimulate the central nervous system, caffeine may increase metabolism by up to 11% and fat burning by up to 13%.
Practically speaking, consuming 300 mg of caffeine per day may allow you to burn an extra 79 calories daily.
This amount may seem small, but it’s similar to the calorie excess responsible for the average yearly weight gain of 2.2 pounds (1 kg) in Americans.
However, a 12-year study on caffeine and weight gain noted that the participants who drank the most coffee were, on average, only 0.8–1.1 pounds (0.4–0.5 kg) lighter at the end of the study.