Do fat burners work?
Barely: the measurable effects are small enough to be lost in a normal week of eating.
Most fat burners are caffeine plus green tea extract plus a list of ingredients with little behind them. The best case from the research is a few extra grams of fat a day, which a slightly bigger portion at dinner erases.
The parts that do move the number are dull: the size of your deficit, your protein, your step count and how long you keep it up. Spend the money on food you will actually eat during a diet.
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- Gholami, F. et al. (2024). Does green tea catechin enhance weight-loss effect of exercise training in overweight and obese individuals? A systematic review and meta-analysis of randomized trials. J Int Soc Sports Nutr 21(1). 10 trials: green tea on top of exercise gave a small extra effect on weight and fat (standardised mean difference about 0.3), with no effect on blood lipids.
- Guest, N.S. et al. (2021). International society of sports nutrition position stand: caffeine and exercise performance. J Int Soc Sports Nutr 18(1). Caffeine is the one ingredient in most fat burners with solid evidence, and that evidence is about performance, not fat loss.
- Hall, K.D. et al. (2012). Energy balance and its components: implications for body weight regulation. Am J Clin Nutr 95(4). What actually sets the rate of fat loss.