Previous cross-sectional studies found that low serum 25(OH)D level was associated with abnormal glucose metabolism and increased HOMA-IR levels [74,75,76,77,78], dyslipidemia [65], impaired fasting glycaemia [74,75,76,77,78,79,80], low plasma adiponectin levels [75,76,77], increased systolic blood pressure [74], decreased high-density lipoprotein-cholesterol [77,78,79,80,81] and accelerated atherosclerosis [82] in obese children aged 5–20 years when compared to normal weight children. This evidence concerns the gene ADIPOQ and metabolic syndrome.