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.

Bioelectrical impedance phase angle in constitutionally lean females, ballet dancers and patients with anorexia nervosa

“…Few data have so far been reported on body composition in constitutionally lean patients and underweight dancers, indicating just a reduction in body fat (Young et al, 1994;Eliakim et al, 2000;Yannakoulia et al, 2000;Scalfi et al, 2001;Matthews et al, 2006;Bossu et al, 2007). The results of this study show that subcutaneous skinfolds and the percentage of body fat between the three groups of underweight patients (who had similar BMI) were largely comparable and that no differences emerged due to chronic underfeeding (anorectic patients) or regular physical exercise (dancers).…”

Should amenorrhea be a diagnostic criterion for anorexia nervosa?

“…Ghrelin was higher among AN women while leptin levels were significantly lower. Similarly, another small study of seven constitutionally thin women, seven normal controls, and six patients with restricting subtype AN (AN-R) 12 found that AN patients consumed a significantly smaller percentage of lipids and had significantly less fat mass percentage though the groups had comparable total energy expenditure. Women with AN also had significantly lower free thyroid hormone T3, IGF-1 and leptin when compared with normal controls and constitutionally thin women.…”

Constitutional Thinness: Unusual Human Phenotype of Low Bone Quality

“…Inclusion criteria were as follows: BMI between 12.0 and 16.5 kg/m 2 , called "severe underweight" according to the World Health Organization classification (15), stable throughout the growth period until the age of 18 (14); presence of physiological menstruation without estrogen-progestin therapy; and desire for weight gain as the main reason for medical consultation.…”

“…These young women are severely thin but continue to have a close-to-normal FM percentage, normal physiological menstrual cycles, and no detectable abnormalities of cortisol, IGF-I, or free T 3 secretory patterns (13), and normal energy metabolism (14). In this context, we wanted to determine whether constitutional thinness could still represent a phenotype of impaired bone quality, in terms of bone mass, bone macroarchitecture and microarchitecture, and bone turnover.…”