Objective: Evidence of the association between vitamin D, insulin resistance, and oral disposition index (oDI) in obese children and adolescents is limited. To fill this research gap, we measured serum 25-hydroxyvitamin D (25[OH]D) levels in obese children and analyzed the relationship between serum 25(OH)D levels and glucose homeostasis.
Methods: Altogether, 348 obese and 445 nonobese children and adolescents (age, 6 to 16 years) were enrolled in this study. Obese children were divided into 4 subgroups: normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and combined IFG and IGT (IFG+IGT) according to oral glucose tolerance test results. We measured serum 25(OH)D levels and calculated the homeostasis model assessment (HOMA) of insulin resistance (IR), the whole-body insulin sensitivity index (WBISI), and the disposition index.
Results: The levels of 25(OH)D in the obese group were significantly lower than in the nonobese group; serum 25(OH)D level in the NGT subgroup was higher than those of the other 3 subgroups, and it was significantly inversely correlated with logHOMA-IR (r = -0.090; P = .045) and positively correlated with logWBISI and logHOMA-oDI (r = 0.091, P = .049; and r = 0.108, P = .046, respectively). Obese patients with vitamin D deficiency thus have a significantly higher risk of disturbances in glucose metabolism.
Conclusion: 25(OH)D deficiency or insufficiency is quite common in obese children and adolescents in Zhejiang, China. Obese patients with 25(OH)D deficiency (<30 nmol/L) are shown to be at higher risk for abnormal glucose metabolism.