Flavanols are potential anti-obesity agents, a systematic review and meta-analysis of controlled clinical trials

Background: The anti-obesity potential of flavonoids has been shown by animal and human studies. In this meta-analysis, we systematically reviewed controlled clinical trials and quantified the effects of flavonoids and flavonoid subclasses on obesity-related anthropometric measures. Methods and results: PubMed, EMBASE, Scopus, Web of Science, and ProQuest databases were searched to identify trials examining the effect of flavonoids on body mass index (BMI), waist circumference, and body fat percentage. Fifty eight trials passed the eligibility process. Analysis endpoints were calculated as the mean difference between baseline and post-treatment. Flavonoids were in subclasses of flavanols, flavonols, isoflavones, flavanones, anthocyanins, and proanthocyanidins. They were mostly in the form of supplements and dosages varying from 40 to 1300 mg/day. Among flavonoid subclasses, flavanols showed potential for decreasing BMI, in the overall population (mean difference (MD) = −0.28 kg/m 2 , P = 0.04; n = 21) and in the subgroups of Asians (MD = −0.42 kg/m 2 ; P = 0.046; n = 13), ages < 50 years (MD = −0.50 kg/m 2 ; P = 0.008; n = 14), BMI ≥ 25 kg/m 2 (MD = −0.30 kg/m 2 ; P = 0.049; n = 15), and at doses ≥ 500 mg/day (MD = −0.36 kg/m 2 ; P = 0.049; n = 12). Isoflavones also decreased BMI of non-Asian populations (MD = −0.26 kg/m 2 ; P = 0.035; n = 13) and doses ≥ 75 mg/day (MD = −0.34 kg/m 2 ; P = 0.027; n = 8). In the overall assessment, flavanols also decreased waist circumference (MD = −0.60 cm; P = 0.02; n = 18) but had no significant effect on body fat percentage. The available trials did not reveal significant effects from flavonols, flavanones, and anthocyanins on the specified anthropometric measures. Conclusions: Overall results of this meta-analysis showed that flavanols have potential against obesity.