Background: A combination of tyrosine, capsaicin, catechines and caffeine may stimulate the sympathetic nervous system and promote satiety, lipolysis and thermogenesis. In addition, dietary calcium may increase fecal fat excretion. Objective: To investigate the acute and subchronic effect of a supplement containing the above mentioned agents or placebo taken t.i.d on thermogenesis, body fat loss and fecal fat excretion. Design: In total, 80 overweight-obese subjects ((body mass index) 31.272.5 kg/m 2 , mean7s.d.) underwent an initial 4-week hypocaloric diet (3.4 MJ/day). Those who lost44% body weight were instructed to consume a hypocaloric diet (À1.3 MJ/day) and were randomized to receive either placebo (n ¼ 23) or bioactive supplement (n ¼ 57) in a double-blind, 8-week intervention. The thermogenic effect of the compound was tested at the first and last day of intervention, and blood pressure, heart rate, body weight and composition were assessed. Results: Weight loss during the induction phase was 6.871.9 kg. At the first exposure the thermogenic effect of the bioactive supplement exceeded that of placebo by 87.3 kJ/4 h (95%CI: 50.9;123.7, P ¼ 0.005) and after 8 weeks this effect was sustained (85.5 kJ/4 h (47.6;123.4), P ¼ 0.03). Body fat mass decreased more in the supplement group by 0.9 kg (0.5; 1.3) compared with placebo (Po0.05). The bioactive supplement had no effect on fecal fat excretion, blood pressure or heart rate. Conclusion: The bioactive supplement increased 4-h thermogenesis by 90 kJ more than placebo, and the effect was maintained after 8 weeks and accompanied by a slight reduction in fat mass. These bioactive components may support weight maintenance after a hypocaloric diet.