Vitamin D to Improve Glucose Metabolism and Reduce Inflammation in Obese Adolescents

The alarming rise in pediatric obesity over the past few decades has been associated with an
increase in the occurrence of impaired glucose tolerance and inflammation in children and
adolescents. These conditions are part of the "metabolic syndrome", and children with risk
factors such as these are much more likely to develop cardiovascular disease or diabetes as
adults compared with their lean peers. Within the last few years there has been a growing
body of evidence that optimizing vitamin D (vit D) status may alleviate these
obesity-associated complications. Further, there is also research that shows that the better
the vit D status of overweight individuals, the more favorably they respond to dieting by
losing more body fat. The prevalence of vit D deficiency/insufficiency in the North American
population has been classified as an "epidemic" by experts in the field and obese teens are
considered at an even greater risk for deficiency because they tend to store vit D in their
fat stores which is not readily mobilized for use by the body. The investigators' project
will study the effects of optimizing the vit D status of obese adolescents on markers of
glucose metabolism and inflammation. Obese teens attending an established adolescent weight
loss clinic will be supplemented with high-dose vit D for 6 months (mos) which will be
administered concurrently with their standard medical care and treatment. At baseline, 3 mos
and 6 mos the investigators will measure vit D status, serum markers of insulin sensitivity
and glucose metabolism; serum markers of inflammation; and body weight/height and waist
circumference. At baseline and 6 mos only the investigators also measure body composition
(percent body fat by dual-energy x-ray absorptiometry) and confounding lifestyle factors
known to affect vit D, glucose metabolism or inflammation (e.g., nutrient intake, physical
activity, sun exposure, pubertal stage). Results gleaned from this study will help to
advance the prevention and treatment of obesity-related complications and have the potential
to lead to significant reductions in healthcare costs and co-morbidities.