Comparison of Insulin Resistance in Lean and Obese Adults with Type 2 Diabetes Mellitus- A Cross-sectional Study

Abstract

Introduction: Insulin Resistance (IR) can develop into type 2 diabetes mellitus and is closely associated with obesity. However, the non-obese population has also shown a predisposition to the risk of IR due to genetics. Aim: To assess the relationship between IR and obesity in Type 2 Diabetes Mellitus (T2DM) by comparing the proportion of subjects with IR in lean and obese T2DM and to identify the factors predicting IR in T2DM. Materials and Methods: A cross-sectional, hospital-based study was done at Department of Medicine of RL Jalappa hospital, Kolar, Karnataka on 106 T2DM patients aged >18 years. The study population was grouped into lean (BMI <19 kg/m2) and obese adults (BMI >30 kg/m2). IR was calculated using Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) and was considered as primary outcome variable. Obesity was considered as primary explanatory variable. Age, Gender, fasting insulin, C-peptide, Fasting Blood Sugar, Glycated haemoglobin (GHB or HbA1c) were the other explanatory variables. Descriptive analysis was carried out using mean and standard deviation for quantitative variables, frequency and proportion for categorical variables. Chi-square test was used to test statistical significance between the groups. Univariate logistic regression analysis was done to identify the predictors of IR. IBM Statistical Package for Social Sciences (SPSS) version 22 was used for statistical analysis. The p-value <0.05 was considered to be statistically significant. Results: The 106 subjects involved in the study had a mean age of 53.88±9.21 years. 44 subjects (41.5%) had IR. Obese to lean diabetic patients were in the ratio of 1:4. The proportion of obese diabetic subjects was (n=84, 79.2%) whereas lean diabetics were (n=22, 20.8%). The proportion of obese diabetic subjects with IR was 38.1% while the proportion of lean diabetic subjects with IR was 54.55%, but this difference was statistically not significant (p=0.163). On univariate logistic regression analysis, fasting insulin (odds ratio of 2.442 with 95% CI of 1.665 to 3.851, p<0.001**) and C-peptide (odds ratio of 1.446 with 95% CI of 1.123, p=0.004) were statistically significant factors attributing to IR. Conclusion: There was no significant relationship between IR and obesity. IR was independently associated with Fasting insulin levels and C-peptide levels.