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

OBJECTIVE: 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. DESIGN: Prospective, longitudinal, observational study. SUBJECTS: In total, 155 subjects (72 males and 83 females, age range: 18-55 y; BMI: 17.5-63.4 kg/m(2)) were evaluated. In total, 43 (26 m and 17 f; BMI: 28.9 +/- 1.1 kg/m(2), mean +/- s.e.m.) of them were reassessed 10-12 y later. MEASUREMENTS: Anthropometric and body composition (bioimpedance analysis) parameters and RMR (indirect calorimetry) were taken at baseline and after 10-12 y. RESULTS: Subjects (15 m, 8 f) who gained body weight (arbitrarily defined as a change in body weight greater than or equal to5 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). CONCLUSION: A low RMR normalized for FFM appears to be associated with body weight gain in the long run in adult Caucasian Italians.