Vitamin D, Childhood Obesity, and Metabolic Risk – A Scoping Review

Vitamin D deficiency and childhood obesity are increasingly recognized as overlapping global health challenges, both of which have substantial implications for long-term wellbeing. Due to the lipophilic nature of vitamin D, excessive adiposity reduces its bioavailability, thereby predisposing overweight and obese children to inadequate circulating 25-hydroxyvitamin D [25(OH)D] concentrations. This deficiency has been associated with impaired bone mineralization, insulin resistance, systemic inflammation, and an elevated risk of type 2 diabetes mellitus, cardiovascular disease, and osteoporosis later in life. Several supplementation strategies for improving vitamin D status in pediatric populations with overweight or obesity have been proposed; however, their efficacy remains inconclusive. Evidence from randomized clinical trials and observational studies indicates that vitamin D supplementation leads to modest increases in serum 25(OH)D levels, with higher-dose regimens producing greater improvements. Findings on the impact of supplementation on metabolic and cardiovascular outcomes are inconsistent, with no clear consensus on the optimal dosing or duration needed to achieve clinically meaningful benefits. Beyond supplementation, lifestyle interventions involving weight reduction through dietary modification and increased physical activity may also contribute to improved vitamin D status, although the interplay between adiposity, vitamin D metabolism, and health outcomes is complex and not yet fully understood. The widespread expression of vitamin D receptors and 1α-hydroxylase in multiple tissues, including adipose tissue, suggests a potential regulatory role in adipogenesis and adipocyte metabolism, which may partly explain the extensive health effects linked to deficiency. This scoping review synthesizes the available evidence on vitamin D, childhood obesity, and metabolic risk, highlighting key research gaps. Further well-designed longitudinal and interventional studies are urgently required to clarify causality, define optimal vitamin D status, and establish effective interventions for improving health outcomes in this vulnerable population.