Anti-obesity effects of resveratrol: comparison between animal models and humans.

The prevalence of obesity has increased rapidly during recent years and has reached epidemic proportions. As a result, the scientific community is interested in active biomolecules which are naturally present in plants and foodstuffs and may be useful in body weight management. In recent years, polyphenols have made up one of the most frequently studied groups among these molecules. Numerous studies have been carried out on animals to analyse the potential anti-obesity effects of resveratrol, a non-flavonoid polyphenol, and a general consensus concerning the body-fat-lowering effect of this compound exists. By contrast, studies in humans have been few so far. Moreover, in these studies, the effectiveness of resveratrol is low. The aims of the present review are to summarize the results reported so far on this topic and to justify the differences observed between animals and humans. It seems that the reduced response to resveratrol in humans cannot be attributed to the use of lower doses in humans because the doses that induce body-fat-lowering effects in rodents are in the same range as those used in human studies. With regard to the experimental period length, treatments were longer in animal studies than in human studies. This can be one of the reasons contributing to the reduced responses observed in humans. Moreover, animals used in the reported studies are young while volunteers participating in human studies are adults, suggesting that resveratrol may be more efficient in young individuals. In addition to differences in the experimental designs, metabolic differences between animals and human cannot be discarded.