Objective: To validate the use of waist circumference to assess reversal of insulin resistance after weight loss induced by bariatric surgery.
Design: In cross-sectional studies, threshold values for insulin resistance were determined with homeostasis model assessment of insulin resistance (HOMA-IR) (algorithm based on fasting plasma glucose and insulin) in 1018 lean subjects and by hyperinsulinemic euglycemic clamp (clamp) in 26 lean women. In a cohort study on 211 patients scheduled for bariatric surgery, HOMA-IR and waist circumference were measured before and 1.5-3 years after weight reduction. In a subgroup of 53 women, insulin sensitivity was also measured using clamp.
Results: The threshold for insulin resistance (90th percentile) was 2.21 (mg dl(-1) fasting glucose × mU l(-1) fasting insulin divided by 405) for HOMA-IR and 6.118 (mg glucose per kg body weight per minute) for clamp. Two methods to assess reversal of insulin resistance by measuring waist circumference were used. A single cutoff value to <100 cm for waist circumference was associated with reversal of insulin resistance with an odds ratio (OR) of 49; 95% confidence interval (CI)=7-373 and P=0.0002. Also, a diagram based on initial and weight loss-induced changes in waist circumference in patients turning insulin sensitive predicted reversal of insulin resistance following bariatric surgery with a very high OR (32; 95% CI=4-245; P=0.0008). Results with the clamp cohort were similar as with HOMA-IR analyses.
Conclusions: Reversal of insulin resistance could either be assessed by a diagram based on initial waist circumference and reduction of waist circumference, or by using 100 cm as a single cutoff for waist circumference after weight reduction induced by bariatric surgery.