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/m2) were evaluated. In total, 43 (26 m and 17 f; BMI: 28.971.1 kg/m2, mean7s.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 Z5 kg) had baseline BMI (29.971.8 vs 28.071.4; 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 (10872.1 vs 12273.1kJ/kg-FFM 24h; P<0.001), although it did not differ significantly between the two groups (11972 vs 12172kJ/kg-FFM 24h; P NS) 10–12y 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.