Resting metabolic rate and body fat distribution in obese Chinese women

Abstract

Body fat distribution is an important predictor of obesity-related complications. Fat distribution pattern may affect the ability to lose weight. Some studies have shown that subjects with lower body obesity (LBO) are more resistant to weight loss than those with upper body obesity (UBO). And this phenomenon has been linked to a higher metabolic rate in UBO subjects than LBO subjects. This findings, however, are not unequivocal. The present study aimed to determine the relationship between resting metabolic rate (RMR) and body fat distribution. This is part of a larger scale study which examines RMR and the ability to lose weight in obese Chinese women. Obese women (41.3 ± 9.6 years old) were divided into three groups according to their waist to hip ratio (WHR): UBO (WHR>0.9, n=12), Intermediate (WHR between 0.85 and 0.9, n=11) and LBO (WHR<0.85, n=11). Dual energy X-ray absorptiometry was used to determine fat mass (FM) and fat-free mass (FFM). RMR was measured in overnight fasted subjects by indirect calorimetry. Mean body mass index (BMI) of these subjects was 31.6 (range: 26-34), with no difference between groups. FFM adjusted for age and BMI (43.5, 41.2 and 38.4 kg, respectively, F(2, 29)=6.01, P<0.01) but not FM was significantly different among groups. FFM as percent of body weight decreases as WHR decreases (r=0.53, P<0.01). RMR, adjusted for age and BMI was found to correlate positively with WHR (r=0.4, P<0.05). The correlation no longer holds when RMR was also adjusted for FFM. Thus, compared to UBO, LBO is associated with a decrease in FFM and RMR. Theoretically, to achieve a similar degree of weight loss, subjects with LBO, compared to subjects with UBO, would need to consume less energy and/or maintain a higher level of physical activity.