The early effects of weight loss surgery on regional adiposity

Background: Weight loss beyond 6 months following laparoscopic adjustable gastric banding (LAGB) is associated with a preferential mobilization of visceral adipose tissue and an improvement in insulin sensitivity in insulin resistant subjects. Because the rate of weight loss is greatest in the first 3 months after LAGB, we investigated the impact of LAGB on changes in regional lipid deposition and insulin sensitivity over this period. Methods: 10 female obese non-diabetic subjects underwent magnetic resonance (MR) imaging and spectroscopy before and 12 weeks after LAGB (using the Swedish band), for the quantification of abdominal subcutaneous and visceral adipose tissue areas and intrahepatic lipid. Fasting blood free fatty acids were analyzed. Insulin sensitivity was monitored by fasting insulin and homeostasis model assessment (HOMA). Results: Median weight loss 12 weeks after gastric banding was 9.5 kg [interquartile range (IQR): -16.5 to -6]. There were significant reductions in median abdominal subcutaneous (-20% [IQR: -24 to -13]) and visceral (-15% [IQR: -49 to -8]) adipose tissue depots as well as plasma free fatty acids (-34% [IQR: -79 to -8]). The amount of weight lost was directly proportional to the initial BMI (r = 0.778; P = 0.008). Visceral fat loss was proportional to initial visceral adiposity (r = 0.80, P = 0.01). There was no significant improvement in insulin sensitivity. Conclusion: Significant fat loss occurs 3 months after LAGB. The absence of a concurrent improvement in insulin sensitivity may reflect the relatively small reduction in visceral adipose tissue at this stage. Improvement in insulin sensitivity beyond 3 months after LAGB may be due to the continued loss of visceral adipose tissue.