The aim of this study was to assess resting energy expenditure in patients with chronic pancreatitis; 33 patients with alcohol-related chronic pancreatitis (group 1: 13 normal weight, group 2: 20 underweight) and 11 undernourished patients without identifiable disease (group 3) were studied. Body composition was determined by bioelectric impedance analysis and fat-free mass was similar among the three groups (76.4 +/- 1.5%, 78.6 +/- 1.3% and 76.8 +/- 2.1% for groups 1, 2, and 3, respectively). The measured resting energy expenditure (REE) was higher than the predicted EE (Harris and Benedict formula and Cunningham's equation) for the underweight patients with chronic pancreatitis (group 2) (P < 0.05), but not for the two other groups. According to Cunningham's equation, 65% of the group 2 patients were hypermetabolic (REE > 110% of predicted EE) versus 23.1% and 20% in groups 1 and 3. When adjusted for fat free mass, REE was significantly (P < 0.01) higher in group 2 (35.0 +/- 0.9 kcal/kg/24 hr) than in the other two groups (30.1 +/- 0.7 kcal/kg/24 hr and 30.8 +/-1.4 kcal/kg/24 hr in groups 1 and 3, respectively). During chronic pancreatitis, weight loss is accompanied by hypermetabolism, which should be taken into consideration during nutritional support.