Lean Type 2 Diabetes Mellitus in Rural Bangladesh: Sociodemographic, Clinical, and Metabolic Characteristics from a Community-Based Cross-Sectional Study
Bishwajit Bhowmik, Tasnima Siddiquee, Sanjida Binte Munir, Hafiza Nasrin, Tanjimul Islam, Rahat Iqbal Chowdhury, Rie Ozaki, Abdul Alim, Faruque Pathan, Hajera Mahtab, Abul Kalam Azad KhanAbstract
Background:
Type 2 diabetes mellitus (T2DM) is commonly associated with obesity and insulin resistance; however, a substantial proportion of South Asians develop diabetes at low body mass index (BMI), indicating metabolic heterogeneity beyond obesity-driven mechanisms.
Objective:
To describe the sociodemographic, clinical, and metabolic characteristics of lean T2DM individuals in rural Bangladesh and compare them with those of normal-weight and overweight/obese T2DM individuals.
Materials and Methods:
A community-based cross-sectional study was conducted among 2293 adults in rural Bangladesh. Of these, 181 individuals with T2DM underwent detailed metabolic assessment. Participants were categorized as lean (<21 kg/m 2 ), normal weight (21–<23 kg/m 2 ), and overweight/obese (≥23 kg/m 2 ) using Asian-specific BMI cutoffs. Standardized anthropometric and biochemical measurements were performed. Insulin resistance and β-cell function were assessed using the Homeostatic Model Assessment indices for insulin resistance (HOMA-IR) and β-cell function (HOMA-β), respectively. Statistical analyses included analysis of variance, chi-square tests, and multinomial logistic regression.
Results:
Among individuals with T2DM, 17.7% were classified as lean. Lean individuals had lower socioeconomic status and dietary energy intake and exhibited reduced β-cell function and lower insulin resistance compared with overweight/obese individuals, who showed higher blood pressure, adverse lipid profiles, and greater prevalence of insulin resistance and dyslipidemia. Glycemic indices were lower in lean individuals, suggesting early-stage or newly diagnosed diabetes. However, when applying the conventional BMI cutoff for lean T2DM (i.e., BMI < 18.5 kg/m 2 ), only 5% met the standard definition of lean T2DM.
Conclusion:
Two T2DM phenotypes coexist: a β-cell-deficient lean form and an insulin-resistant overweight/obese form. Conventional lean T2DM represents a small subgroup, highlighting the need for context-specific BMI thresholds in South Asian populations.