Vitamin D deficiency in adolescents with obesity - Altered metabolism or environmental factors?

Introduction: obesity childhood is related to vitamin D deficiency. The aim of this study was to compare vitamin D status between adolescents with obesity living in an urban area and in a rural area. We hypothesized that environmental factors would be decisive in reducing the body content of vitamin D in patients with obesity. Methods: a cross-sectional clinical and analytical study (calcium, phosphorus, calcidiol and parathyroid hormone) was carried out in a group of 259 adolescents with obesity (BMI-SDS > 2.0), 249 adolescents with severe obesity (BMI-SDS > 3.0) and 251 healthy adolescents. The place of residence was categorized as urban or rural. Vitamin D status was defined according to the US Endocrine Society criteria. Results: vitamin D deficiency was significantly higher (p < 0.001) in severe obesity (55 %) and obesity groups (37.1 %) than in the control group (14 %). Vitamin D deficiency was more frequent in severe obesity (67.2 %) and obesity groups (51.2 %) living in urban areas than in those living in rural areas (41.5 % and 23.9 %, respectively). The patients with obesity living in urban residence did not present significant seasonal variations in vitamin D deficiency in contrast to those patients with obesity living in rural residence. Conclusions: the most probable mechanism for vitamin D deficiency in adolescents with obesity, rather than altered metabolic is the environmental factors (sedentary lifestyle and lack of adequate sunlight exposure).