Low relative resting metabolic rate and body weight gain in adult Caucasian Italians

Abstract

To investigate the relationship between resting metabolic rate (RMR) and subsequent changes in body size and degree of fatness in a group of adult Caucasian Italians. Prospective, longitudinal, observational study. In total, 155 subjects (72 males and 83 females, age range: 18-55 y; BMI: 17.5-63.4 kg/m2) were evaluated. In total, 43 (26 m and 17 f; BMI: 28.9+/-1.1 kg/m2, mean+/-s.e.m.) of them were reassessed 10-12 y later. Anthropometric and body composition (bioimpedance analysis) parameters and RMR (indirect calorimetry) were taken at baseline and after 10-12 y. Subjects (15 m, 8 f) who gained body weight (arbitrarily defined as a change in body weight > or = 5 kg) had baseline BMI (29.9+/-1.8 vs 28.0+/-1.4; P = NS) and body composition in terms of fat mass (FM%) and fat-free mass (FFM kg) comparable to those of the subjects (11 m, 9 f) whose body weight remained stable. Baseline RMR was significantly lower in subjects who gained weight than in those who did not (108+/-2.1 vs 122+/-3.1 kJ/kg-FFM 24 h; P < 0.001), although it did not differ significantly between the two groups (119+/-2 vs 121+/-2 kJ/kg-FFM 24 h; P = NS) 10-12 y later. Baseline RMR was inversely correlated to both change in body weight (r = -0.57; P < 0.001) and FM (r = -0.50; P < 0.001). A low RMR normalized for FFM appears to be associated with body weight gain in the long run in adult Caucasian Italians.