title: Energy expenditure adjusted for body composition differentiates constitutional thinness from both normal subjects and anorexia nervosa.
abstract: Constitutional thinness (CT) is characterized by a low and stable body mass index (BMI) without any hormonal abnormality. To understand the weight steadiness, energetic metabolism was evaluated. Seven CT, seven controls, and six anorexia nervosa (AN) young women were compared. CT and AN had a BMI <16.5 kg/m(2). Four criteria were evaluated: 1) energy balance including diet record, resting metabolic rate (RMR) (indirect calorimetry), total energy expenditure (TEE) (doubly labeled water), physical activity; 2) body composition (dual-energy X-ray absorptiometry); 3) biological markers (leptin, IGF-I, free T3); 4) psychological profile of eating behavior. The normality of free T3 (3.7 +/- 0.5 pmol/l), IGF-I (225 +/- 93 ng/ml), and leptin (8.3 +/- 3.4 ng/ml) confirmed the absence of undernutrition in CT. Their psychological profiles revealed a weight gain desire. TEE (kJ/day) in CT (8,382 +/- 988) was not found significantly different from that of controls (8,793 +/- 845) and AN (8,001 +/- 2,152). CT food intake (7,565 +/- 908 kJ/day) was found similar to that of controls (7,961 +/- 1,452 kJ/day) and higher than in AN (4,894 +/- 703 kJ/day), thus explaining the energy metabolism balance. Fat-free mass (FFM) (kg) was similar in CT and AN (32.5 +/- 2.9 vs. 34.1 +/- 1.9) and higher in controls (37.8 +/- 1.6). While RMR absolute values (kJ/day) were lower in CT (4,839 +/- 473) than in controls (5,576 +/- 209), RMR values adjusted for FFM were the highest in CT. TEE-to-FFM ratio was also higher in CT than in controls. Energetic metabolism balance maintains a stable low weight in CT. An increased energy expenditure-to-FFM ratio differentiates CT from controls and could account for the resistance to weight gain observed in CT.
authors.affiliation: Service d'endocrinologie diabète et maladies métaboliques, Hôpital Bellevue, CHU Saint Etienne, 42055 Saint Etienne Cedex 02, France. bruno.estour@chu-st-etienne.fr
authors.forename: Cécile
authors.initials: C
authors.lastname: Bossu
authors.forename: Bogdan
authors.initials: B
authors.lastname: Galusca
authors.forename: Sylvie
authors.initials: S
authors.lastname: Normand
authors.forename: Natacha
authors.initials: N
authors.lastname: Germain
authors.forename: Philippe
authors.initials: P
authors.lastname: Collet
authors.forename: Delphine
authors.initials: D
authors.lastname: Frere
authors.forename: François
authors.initials: F
authors.lastname: Lang
authors.forename: Martine
authors.initials: M
authors.lastname: Laville
authors.forename: Bruno
authors.initials: B
authors.lastname: Estour
mesh_terms: D000273:Adipose Tissue / Q000033:anatomy & histology; D000293:Adolescent; D000328:Adult; D000856:Anorexia Nervosa / Q000097:blood / Q000175:diagnosis* / Q000523:psychology; D001481:Basal Metabolism; D001823:Body Composition; D001824:Body Constitution; D015992:Body Mass Index; D001835:Body Weight; D003937:Diagnosis, Differential; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D020738:Leptin / Q000097:blood; D013851:Thinness / Q000097:blood / Q000175:diagnosis* / Q000523:psychology
chemical_list: D020738:Leptin