Elevated diet-induced thermogenesis and lipid oxidation rate in Crohn disease

Background: Although malnutrition is frequently observed in Crohn disease ( CD), its cause is not clear. Regulation of energy metabolism and diet-induc ed thermogenesis (DIT) have not been adequately studied in CD, Objective: The aim was to study DIT and substrate oxidation in patients wit h inactive ileal CD. Design: After a test meal providing 50.2 kJ/kg body wt, DIT was assessed by indirect calorimetry performed over 360 min in 18 CD patients and 12 healt hy volunteers matched for age, sex, weight, and height. Body composition wa s evaluated with the labeled-water-bolus injection technique. Results: Fat-free mass did not differ significantly between groups, but CD patients had markedly lower fat mass than control subjects (13.8 +/- 5.63 c ompared with 19.0 +/- 3.49 kg; P < 0.001). Nonprotein respiratory quotient was lower in CD patients than control subjects (0.80 +/- 0.04 compared with 0.86 +/- 0.03; P < 0.001), Average respiratory quotient between 75 and 150 min after the test meal was 0.85 +/- 0.03 in CD patients and 0.91 +/- 0.02 in control subjects (P < 0.001). Lipid oxidation rate was higher in CD pat ients than in control subjects (2.26 +/- 1.13 compared with 1.50 +/- 0.75 k J/min; P < 0.05). DIT was higher in CD patients than in control subjects (9 .89 +/- 1.93% compared with 5.67 +/- 0.91% of energy intake; P < 0.001). Conclusions: Patients with inactive ileal CD had significantly higher DIT a nd lipid oxidation rate than do healthy volunteers. These results may expla in why CD patients have difficulty maintaining adequate nutritional status, and the findings also suggest that a diet relatively rich in fat may attai n better energy balance.