Obesity has emerged as a risk factor in the onset of bone, muscle and adipose tissue impairments that are further aggravated by vitamin D deficiency. A link of an active bone-muscle-adipose axis is represented by Wnt pathway. This study will test the hypothesis that vitamin D improves bone, muscle, and adipose tissue health through a positive modulation of Wnt pathway. It will be carried out a double-blind, placebo-controlled study of cholecalciferol supplementation in vitamin D-deficient obese adults. Specific aims will be: 1) to test the direct effect of vitamin D on Wnt signaling in bone, muscle, and adipose tissue; 2) to evaluate muscle mass and strength; 3) to assess changes in vitamin D status across different administration strategy (weekly, fortnightly, monthly). This study will provide not only insight of new mechanisms involved in the pathophysiology of obesity-related musculoskeletal impairments but also evidence for new treatment recommendations for vitamin D deficiency in obesity.