To determine whether there was a metabolic basis for recent reports that bulimic patients had low energy requirements for weight maintenance, energy expenditure measurements were made in 15 women with bulimia nervosa during abstinence from bingeing and vomiting. Resting metabolic rate, adjusted for differences in lean body mass, was significantly lower in bulimics (mean +/- SE, 4201 +/- 126 kJ/d) than healthy volunteers (4694 +/- 172 kJ/d). Bulimic patients had a blunted increase in oxygen consumption in response to low and moderate levels of exercise (421 +/- 16 and 689 +/- 17 mL/min) compared with values for healthy volunteers (491 +/- 28 and 795 +/- 26 mL/min). Plasma triiodothyronine (1.1 +/- 0.07 vs 1.4 +/- 0.08 nmol/L) levels, plasma norepinephrine levels in supine (0.58 +/- 0.04 vs 1.06 +/-0.17 nmol/L) and standing (1.34 +/- 0.15 vs 2.46 +/- 0.30 nmol/L) subjects, and the increase in norepinephrine levels during orthostatic challenge (0.76 +/- 0.15 vs 1.40 +/- 0.25 nmol/L) all were significantly less in bulimics than volunteers. These results are consistent with previous reports of decreased energy requirements for weight maintenance and decreased plasma levels of metabolism-related hormones in patients with bulimia. However, the effects of reduced energy intake in metabolic studies of patients with bulimia need to be further investigated.