Aim The purpose of our research was to evaluate the Vitamin D deficiency amongst obese children and teens. Methodology A double–blind randomized placebo–controlled trial. Vitamin D deficient patients (<30 ng/ml level of vitamin D) aged 6–14, participating in multidisciplinary weight management program were randomly allocated to receiving vitamin D (1200 IU) or placebo for the first 26 weeks of the intervention. Results Out of the 130 qualified patients, 109 (72%) completed a full cycle of four visits scheduled in the program. There was no difference in the level of BMI (body mass index) change – both raw BMI and BMI centiles. Although the reduction of BMI centiles was greater in the vitamin D vs. placebo group (4.28± 8.43) vs. (2.53± 6.10) the difference was not statistically significant (p = 0.319). Conclusion Our study ads substantial results to support the thesis on no effect of vitamin D supplementation on body weight reduction in children and adolescents with vitamin D insufficiency undergoing a weight management program

vitamin D; obesity; weight–loss; body composition.