This study aims to assess the effect of insulin resistance (IR) on 12-month weight outcome in adults with class 3 obesity without diabetes attending a multidisciplinary weight management program (WMP).
Adults (≥18 years) with body mass index (BMI) ≥40kg/m2 and no diabetes enrolled in a WMP in Sydney, Australia between January 2019 and February 2024, who completed 12 months of the program were included. Demographic details, anthropometric variables and clinical data were collected. IR was calculated using the HOMA-IR formula: (Fasting Plasma Glucose [mmol/L] × Fasting Insulin [pmol/L]) ÷ 135. T-tests were used to assess differences between group means. Univariate and multivariate regression analyses were used to evaluate the association between IR and weight change outcomes using SPSS v29.
A total of 231 patients were included with mean (±standard deviation) age 45.5±13.5 years, weight 154.7±35.2 kg, female (69.7%) and Caucasian (79.3%). At baseline, 89.1% of the cohort had insulin resistance (HOMA-IR >2.71) and the mean baseline HOMA-IR was 8.1±6.1. At 12 months, significant weight loss was observed in this cohort (-4.6±7.4% baseline weight, p<0.001), with no change in HOMA-IR (p=0.628). Patients with no IR at baseline (n=21), compared to patients with IR (n=172), had significantly lower weight at baseline (134.9±24.7 kg vs 160.0±35.9 kg, p<0.001). There was no significant difference in weight change between the two groups over 12 months (no IR: -5.8±11.2% vs IR: -4.5±7.1%; p=0.612). On univariate and multivariate regression analyses, adjusting for age and sex, log-transformed HOMA-IR was significantly associated with baseline weight (univariate p<0.001, multivariate p=0.001) but not weight change over 12 months (univariate p=0.535).
IR is highly prevalent among adults with class 3 obesity without diabetes and is positively associated with weight. These findings suggests that IR did not affect weight outcomes in adults with class 3 obesity without diabetes undergoing a 12-month multidisciplinary WMP.