Does cayenne pepper help with weight loss and fat burning?
Studies show that cayenne pepper produces a modest increase in fat burning and energy expenditure, and contributes to eating slightly less at a meal. As a supplement to a low-calorie diet, it has a biologically well-supported contribution.
Cayenne pepper contains capsaicin, and many groups of studies show that this compound modestly increases the amount of energy the body burns. Resting metabolism rises by an average of 34 to 59 kilocalories per day, and the body burns relatively more fat instead of carbohydrates. This effect appears strongest in people who are overweight. In people of normal weight, no clear effect on fat burning was found.
For those looking to eat a little less, cayenne pepper may also help: people who take capsaicinoids before a meal eat on average around 74 kilocalories less. That said, results vary considerably across studies, and at least 2 mg of capsaicinoids appears to be needed for this effect. Over the long term, at everyday kitchen doses, red pepper does not noticeably increase total energy expenditure. What does come up repeatedly: greater fat burning, and a slower return of the hunger that normally sets in on a low-calorie diet.
The effect on appetite is not straightforward. Some studies find less hunger and less belly fat with regular use, but a broad analysis of plant extracts for appetite suppression found no consistent benefit for cayenne pepper. For the activation of brown fat tissue, a much-discussed mechanism, the evidence in people is still too thin to draw conclusions, even though animal studies are more promising.
Whether you personally benefit also depends partly on your genetic make-up. Small studies point to inherited differences in how well people tolerate capsaicin, which determines how strong the effect is. This is interesting for the future of personalised nutrition advice, but is not yet practically applicable.
This answer draws on multiple groups of studies, summarised in eight combined analyses. The effects on energy expenditure and fat burning are the best documented. The evidence for appetite suppression is conflicting, and the evidence for genetic variation and brown fat activation is thin. In the most recent combined analysis on red pepper and energy expenditure, two of the four authors had ties to the herbal industry; those findings have been taken into account but interpreted with some caution.
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