AbstractCyperus rotundus L. (Cyperaceae; C. rotundus) is an Indian medicinal plant demonstrated to exert multiple health benefits. The purpose of the present study was to test the biological efficacy of C. rotundus tubers extract on weight control in obese Zucker rats. It was demonstrated that administration of 45 or 220 mg/kg/day of C. rotundus tubers hexane extract for 60 days in Zucker rats induced a significant reduction in weight gain without affecting food consumption or inducing toxicity. In vitro, 250 µg/mL of this extract was able to stimulate lipolysis in 3T3‐F442 adipocytes suggesting that this medicinal plant contains activators of β‐adrenoreceptors (AR). The binding assay performed on the rat β3‐AR isoform, known to induce thermogenesis, demonstrated that C. rotundus tubers extract can consistently and effectively bind to this receptor. These data suggest that the effect on weight gain exerted by C. rotundus tubers extract may be mediated, at least partially, through the activation of the β3‐AR. In conclusion, C. rotundus tubers extract prove to be a new herbal supplement for controlling body weight preferentially in β3‐AR sensitive species. Copyright © 2007 John Wiley & Sons, Ltd.