To assess whether energy from alcohol is efficiently utilized to maintain body mass, we examined changes in energy intake of young women when they drank alcohol. The women ate controlled diets typical of the American diet with regard to macronutrients. Body weights were controlled to within 1 kg of entry level weights. The subjects were given alcohol (30 g/d) and no alcohol treatments for 3 mo each in a crossover design. The treatments were isoenergetic; for the no alcohol treatment alcohol energy was replaced with energy from carbohydrate. The average change in energy intake associated with the alcohol treatment was negligible when all subjects were considered collectively. There was, however, a divergence in response between lean and heavy subjects. Fifteen women required, on average, an additional 886 +/- 147 (mean +/- SEM) kJ/d to maintain body weight during the alcohol treatment, and these women were leaner (body mass index 22.6 +/- 0.8 kg/m2 vs. 25.2 +/- 1.0, P < 0.05) than the 22 women who required, on average, 559 +/- 139 fewer kJ/d when on the alcohol treatment. This study suggests that all subjects do not use energy from alcohol with equal efficiency.