Biochemical Basis of Insulin Resistance in Obese Adolescents in Urban South West Nigeria: A Cross-Sectional Analytical Study

Childhood and adolescent obesity has risen dramatically in urban Nigeria over the past decade, and its biochemical consequences including insulin resistance and early metabolic syndrome represent an emerging preventive health priority. This study analytically investigates the biochemical basis of insulin resistance in obese adolescents in urban South West Nigeria, examining the contributions of adipokines, inflammatory markers, and lipid metabolism to insulin resistance pathogenesis. A cross-sectional analytical design enrolled one hundred obese adolescents (BMI z-score above two) and eighty normal-weight controls aged twelve to eighteen years from secondary schools in Lagos and Ibadan. Fasting blood was analysed for glucose, insulin, HbA1c, lipid profile, high-sensitivity CRP, IL-6, TNF-alpha, adiponectin, leptin, and free fatty acids. Insulin resistance was quantified using the homeostasis model assessment of insulin resistance (HOMA-IR). Adiposity was assessed by BMI, waist circumference, and dual-energy X-ray absorptiometry body fat percentage at a collaborating facility. Obese adolescents showed significantly higher HOMA-IR, fasting insulin, triglycerides, LDL-C, leptin, CRP, IL-6, and TNF-alpha, and significantly lower adiponectin and HDL-C compared to controls. Multiple regression analysis identified leptin, adiponectin, TNF-alpha, and free fatty acids as independent predictors of HOMA-IR after adjusting for BMI and sex. Mediation analysis suggested that adipokine dysregulation and chronic low-grade inflammation are important intermediary mechanisms linking central adiposity to insulin resistance in this population. These findings provide biochemical targets for early intervention in adolescent obesity. Keywords: insulin resistance, obesity, adolescents, adipokines, South West Nigeria.