Malabsorption is a major contributor to underweight in Crohn's disease patients in remission.

Objective: Undernutrition has been reported in 65-75% of patients with Crohn's disease. The present study aimed at identifying the relative contribution of malnutrition-causing factors in patients with Crohn's disease in remission.

Methods: Sixteen patients with Crohn's disease (age 19-57 y) in remission (Crohn's Activity Disease Index < 150) were included in the study. Their weight was stable for >3 mo and they were off steroids. They all completed 3-d food records and concomitantly collected stools. Self-reported food records were analyzed and energy content in stools was determined by a direct bomb calorimeter. Resting energy expenditure (REE) was studied by indirect calorimetry and body composition by dual-energy X-ray absorptiometry. The study cohort was divided into two groups, with a body mass index (BMI) equal to 18.5 kg/m(2) serving as a cutoff point.

Results: Subjects with lower BMIs tended to have less lean body mass (P = 0.006), less bone mineral density (P = 0.006), and lower REE (P = 0.003). No correlation was found between BMI and energy intake but the percentage of malabsorption was negatively correlated with BMI (P = 0.07). When dividing the study based on a BMI of 18.5 kg/m(2), no difference was found in caloric intake or REE between groups but subjects with lower BMIs had significant prominent malabsorption compared with the others (21.1 +/- 9.8% versus 11.7 +/- 3.5%, P = 0.015).

Conclusion: In the presence of similar energy intake, REE does not seem to contribute to lower BMI, although nutrient malabsorption is higher in malnourished patients with Crohn's disease in remission. We suggest that malabsorption be evaluated in patients with Crohn's disease who fail to gain weight during disease remission to establish their extra caloric requirements.