BMR variability in women of different weight

Background & aims Non-exercise activity thermogenesis (NEAT) and substrate oxidation are significant components of Energy Balance; their regulation may be modulated according to nutritional status and their impairment has been advocated as a factor facilitating the development of excess body fat. Methods In this study body composition, resting metabolic rate (RMR), fidgeting as a component of NEAT and respiratory quotient (RQ), an index of preferential substrate oxidation, have been evaluated in 80 young women: 20 restrictive anorexia nervosa (rAN: BMI 15.1±1.6 kg/m2); 20 constitutional leanness (CL: BMI 17.2±1.0); 20 obese patients (Ob: BMI 43.8±10.0) and 20 controls (CTR: BMI 21.7±2.4). Results Fat free mass, fat mass and RMR progressively increased from rAN to Ob (p<0.05). Fidgeting was higher in CL (67.2±27.2 kcal; p<0.05) than in the other groups. Lipid oxidation, evaluated with RQ showed a negative correlation with fidgeting in CL (r=−0.433; p<0.05) and positive in Ob (r=0.572; p<0.05) and in rAN (r=0.434; p<0.05). Conclusion Our findings support the regulatory function of NEAT, its protective role to prevent excess body fat accumulation and its positive relation with fat oxidation in CL.