• Assesment of insulin sensitivity before and after vitamin D3 supplementation index [ Time Frame: 12 weeks ] [ Designated as safety issue: Yes ]
  

• Monitor effect of vitamin D supplementation with 400 and 2,000 IU/day for 12 weeks on lipids and c-reactive protein. [ Time Frame: 12 weeks ] [ Designated as safety issue: Yes ]
  

The problem of childhood obesity has reached epidemic proportions both nationally and internationally. The prevalence of obesity has tripled in the last three decades and currently 16 % of American adolescents are obese. Nearly 30% of obese adolescents demonstrate a metabolic syndrome characterized by insulin resistance and dyslipidemia. These abnormalities lead to the development of type 2 diabetes mellitus and to increased cardiovascular morbidity and mortality. Obesity is a well-known risk factor for vitamin D insufficiency and up to 80% of obese adults have been found to be insufficient in vitamin D. Observational studies in adults have shown consistent associations between low vitamin D status and prevalence of type 2 diabetes mellitus and metabolic syndrome. There is paucity of data on the prevalence of vitamin D insufficiency and its implications in obese adolescents. It is also not known whether treatment of vitamin D insufficiency in children or adults might result in improvement in insulin resistance and cardiovascular risk factors.

Hypotheses: We hypothesize that vitamin D insufficiency correlates positively with insulin resistance and cardiovascular risk in obese adolescents and that vitamin D3 supplementation decreases insulin resistance and cardiovascular risk factors in this population.

Objectives:

1. Determine if there is any correlation between serum 25(OH)D levels and HOMA-IR, HDL cholesterol and C-reactive protein, in obese adolescents.
2. Study the impact of vitamin D3 supplementation on various parameters reflecting insulin action, secretion, lipids and C-reactive protein in obese adolescents.