Sex differences in visceral adipose tissue post-bariatric surgery compared to matched non-surgical controls.

Objective and methods: Given the profound weight loss after gastric banding and bypass we compared fat compartmentalization by whole body magnetic resonance imaging in women and men after these procedures to two groups of non-surgical controls who were either matched for age, weight and height or were of lower body mass index (BMI). Result: In women post-surgery (n=17; BMI 31.7 kg/m 2 ) there was lower visceral adipose tissue (VAT) (1.4 vs 2.5 kg; P<0.01) compared with matched controls (n=59; BMI 32.1 kg/m 2 ). In contrast, VAT (5.3 vs 5.4 kg) was nearly identical in men post-surgery (n=10; BMI 34.1 kg/m 2 ) compared with matched controls (n=10; BMI 32.1 kg/m 2 ) even though the degree of weight reduction was not significantly different from women (27.4 vs 32.6%). Furthermore, VAT when adjusted for total adipose tissue (TAT) was 43% less in women post-surgery (1.2 vs 2.1 kg; P=0.03) than in controls with lower BMI (25.1 kg/m 2 ). After adjustment for TAT, subcutaneous adipose tissue in women post-surgery was significantly greater than matched controls (35.1 vs 34.2 kg; P=0.03). There was a significant negative correlation of VAT and the degree of weight loss in women (r=−0.57; P=0.018) but this relationship was not significant in men (r=−0.39; P=0.27). Skeletal muscle was lower in both sexes compared with matched controls (women, 21.8 vs 23.1 kg; men, 32.5 vs 35.5 kg). Conclusion: Prospective studies are necessary to confirm if there is a sexual dimorphism in the effects of bariatric surgery on body composition.