Evidence Level
Strong
Caffeine is the most well-established natural thermogenic agent, with robust evidence for increasing metabolic rate and fat oxidation. The 2019 Tabrizi meta-analysis confirmed significant reductions in body weight and fat. Effects are dose-dependent, with 200-400 mg showing the best risk-benefit profile. Tolerance develops, reducing the acute thermogenic boost, but some metabolic benefit persists with habitual use. Combining caffeine with other thermogenics (EGCG, capsaicin) may enhance effects.