Resting energy expenditure and fat-free mass do not decline during aging in severely obese women

Background & aims: Few studies have investigated the age-related modification of resting energy expenditure (REE) and free fat mass (FFM) in severe obesity. This cross-sectional study analyzed REE and FFM in severely and moderately obese women and in lean subjects at different ages to find the possible differences between obese and lean subjects during aging. Methods: Sedentary women (n = 261) were divided into three groups with different body mass indexes (BMIs): 20.0-24.9; 30-34.9; >40 kg/m2. Each group was then divided into five subgroups: 20-29; 30-39; 40-49; 50-59; 60-69 years. REE was measured with an indirect calorimetric device. The FFM was calculated by bioelectric impedance. Results: The REE in severely obese women was higher than the REE in lean or moderately obese women. The FFM of severely obese women was lower than that of moderately obese or lean women. The aging induced reductions of the REE and FFM in lean and moderately obese subjects, but not in women with severe obesity. Conclusions: This experiment indicates that REE and FFM do not decline during aging in women with BMI > 40, suggesting that the severe obesity induces different age-related adaptations of metabolism and body composition. © 2008 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism.