The relationship between insulin resistance and waist circumference in obese adults seeking weight loss

Abstract

Insulin resistance (IR) is not routinely measured and is associated with serious health problems. A simple, non-invasive, inexpensive gauge of IR is needed. The aim of this project was to assess whether waist could be used as an indicator of IR. Waist (cm) and Homeostatic model assessment (HOMA) score of IR was collected at baseline and quarterly over 12 months from obese (BMI >29-<45) adults (n=151, 108F) undergoing a 6-month weight loss program on standardised energy reduction diets of 5-7.5MJ. Waist was measured at narrowest point between bottom of ribs and top of hips. Fasting venous glucose and insulin, collected by qualified phlebotomists, was used to calculate HOMA. Spearman's correlation was conducted to determine relationships between variables. Mean (ᓄ) baseline BMI, waist and HOMA score was 35.0ᴮ3, 108.4ᱱ.4 and 2.5ᱮ9 respectively. The correlation between waist and HOMA, and change in waist (%) and HOMA from baseline with all timepoints combined was significant (r=0.504, p=0.000; r=0.218, p=0.000). Waist and HOMA at each quarter were significantly correlated (r=0.348-0.501, p<0.005). Both genders showed significant correlations between waist and HOMA and change from baseline (M:r=0.665, p=0.000 & F:r=0.396, p=0.000; M:r=0.279, p=0.006 & F:r=0.193, p=0.002 respectively). Those aged <50 and =50 years showed significant correlations between waist and HOMA (<50:r=0.232-0.454, p<0.005; =50:r=0.207-0.543, p<0.005). Waist was positively correlated with IR regardless of gender, age and timepoint during weight loss. Waist circumference may be a simple, non-invasive, inexpensive indicator of IR. Funding: Australian Postgraduate Award and William Arnott Scholarship