Rubbish! Chilis don't make you lose weight! ...or do they?!

Research on the effect of chili peppers on metabolic rate, continues.

In a study done at McMaster University in Canada, researchers tested the effect of capsinoids (substances present in chili peppers, and related to the more famous compound capsaicin) on energy expenditure, fat burning, and levels of certain molecules in the blood.¹

Twelve healthy male subjects were observed before and after a 90 minute stationary bike ride. During two separate experiments all subjects took (randomly) either a placebo or a treatment containing 10mg capsinoid, so that each subject had results that represented the effect of capsinoids and the effect of placebo. The subjects were tested with respect to oxygen consumption, respiratory exchange ratio (RER), heart rate, perceived exertion, and blood metabolites. Previous research on other andrenergic agonists (like caffeine) showed that these variables are changed by the treatment both during rest and during exercise. However, in the current study effects were mainly significant during rest. The main findings in this study were that, versus a placebo, 10 mg of capsinoids induced a rise in resting oxygen consumption, a decline in RER, an increase in plasma norepinephrine, and a decline in serum free fatty acids at rest. 10 mg of capsinoids also blunted the small but significant rise in blood lactate observed at the onset of exercise seen in the placebo group (0 mg).

This means that capsinoids raise the resting metabolic rate (shown as an increase in oxygen consumption) without increasing resting heart rate (none were observed in the study). Furthermore, the increase in norepinephrine and decline in RER suggest that the body burns more fat at rest. However, the effect of capsinoids on metabolism didn't carry over into exercise, where both groups showed similar metabolic states.

Capsinoids, therefore, represent a useful treatment for patients who want to lose weight, regardless of their level of physical activity.

¹ Josse et al. Effects of capsinoid ingestion on energy expenditure and lipid oxidation at rest and during exercise. Nutrition & Metabolism 7: 65 (2010).