Capsinoid supplements failed to shift weight, waistlines or body fat

Capsinoid supplements are sold on the promise that they help shed fat, and small individual trials have pointed in different directions. Single supplement trials are often short and modest in size, so pooling them is the clearest way to see whether a real effect exists. This review set out to test whether capsinoids change eight separate measures of body size and composition, spanning body weight, BMI, waist circumference, waist-hip ratio, fat mass, fat-free mass, visceral fat area and percentage body fat. It also asked whether any effect grows with the dose taken or the length of supplementation.

The researchers searched four databases from their beginnings until November 2020 for clinical trials of capsinoid supplementation on body composition and anthropometric measures. Thirteen trials met the criteria, contributing 19 effect sizes and 838 participants in total. Every trial compared capsinoid supplementation against a comparator and reported at least one of the eight body measures of interest. Alongside the main pooled analysis, the team ran dose-response analyses to check whether the amount taken or the duration of the study changed the outcome.

The pooled analysis found no significant effect of capsinoids on any of the eight measures: body weight, BMI, waist circumference, waist-hip ratio, fat mass, fat-free mass, visceral fat area and percentage body fat all stayed put. One slice of the data did show a significant reduction in body weight, specifically in trials run on overweight participants that lasted 12 weeks or longer. However, the dose-response analyses found no significant relationship between either the dosage or the study duration and changes in body weight or BMI, which weakens the idea that more or longer simply works better.

This pooled result sits awkwardly against the way capsinoids are marketed, since the headline finding is a null across every obesity indicator measured. The authors conclude that capsinoid supplementation has no significant effect on obesity indicators, while flagging the finding in overweight participants on courses of 12 weeks or more as worth confirming. They call for well-designed randomised trials with larger samples and longer durations. Until those exist, the possible modest benefit in that group remains a hypothesis drawn from a smaller cut of the data rather than an established effect.

For anyone eyeing capsinoid capsules as a fat-loss aid, the fairest reading is that the pooled evidence shows no effect on weight, waist size or body fat. The single encouraging signal applies to overweight people supplementing for 12 weeks or more, and even that is tentative by the authors' own account. This is a reason to treat capsinoid fat-loss marketing with scepticism rather than proof the compounds do nothing in every circumstance. Nothing here supports expecting visible changes in body composition from these supplements alone.