Uncovering hidden vitamin D deficiency in overweight children.

Vitamin D deficiency is disproportionately prevalent among overweight and obese children, with conventional explanations such as poor dietary intake or reduced sun exposure offering only partial insight. Emerging evidence reveals a multifactorial pathophysiology, including sequestration of vitamin D in adipose tissue, altered hepatic metabolism, diminished bioavailability, and inflammation-induced resistance at the tissue level. These mechanisms contribute to a functional deficiency, wherein serum 25-hydroxyvitamin D levels may remain suboptimal despite adequate intake or sun exposure. Obesity-related alterations in vitamin D-binding proteins, receptor expression, and pro-inflammatory signaling further compromise biological activity. Current diagnostic criteria and supplementation guidelines do not fully reflect these physiological complexities, leading to underdiagnosis and insufficient treatment. Personalized approaches-incorporating higher, body composition-adjusted dosing and consideration of inflammatory status-are emerging as promising strategies to restore sufficiency and improve metabolic outcomes. While preliminary evidence supports the safety and efficacy of high-dose supplementation in this population, pediatric-specific clinical trials are lacking. This review synthesizes current understanding of the pathophysiological mechanisms underlying vitamin D deficiency in pediatric obesity and emphasizes the need for individualized, evidence-based interventions to optimize vitamin D status and overall health.