Supplementation with 20,000 IU of cholecalciferol (vit D3) (n = 130) per week in severely obese subjects for 12 months was able to decrease insulin-like growth factor (IGF-I) and the IGF binding protein-3 (IGFBP-3) ratio (IGF-I:IGFBP-3 ratio), which are important markers of insulin resistance, as low serum levels of IGF-I and increased levels of IGFBP-3 are related to increased waist-to-hip ratio, insulin resistance, and cardiovascular disease, whereas GH basal levels are slightly reduced in obese individuals [95,146,147]. This evidence concerns the gene IGFBP3 and Insulin resistance.