Effects of different dosages of vitamin D3 on anthropometric indices, metabolic, bone, and vascular parameters and body composition in overweight or obese children and adolescents

determine the effect of different doses of vitamin D3 supplementation on anthropometric indexes, parameters of metabolic, bone, vascular and body composition in children and adolescents with overweight or obesity

parallel group, single blind, randomized placebo-controlled clinical trial.

overweight and obesity children and adolescents of Tehran, Iran

Inclusion criteria: - Willingness to cooperate - Age 6-13 years - Overweight or obesity Exclusion criteria: - Reluctance to cooperate in any stage of study - Use of any vitamin D supplements - Use of any drugs, affecting metabolism of vitamin D including glucocorticoids, steroids and anticonvulsants such as carbamazepine, phenytoin and phenobarbital

Three intervention groups as follows:oral 2000 IU of vitamin D3 supplement, 1000 IU vitamin D3 supplement, and the control group (600 IU vitamin D3 supplement) for 12 months.

carotid intima media thickness (cIMT), 25 hydroxy vitamin D, parathormone, lipid profile, glucose, insulin, body mass index, fat mass, lean mass, systolic and diastolic blood pressure, calcium, phosphorus

Children and adolescents will be randomized using stratified block randomization method in each intervention group (2000 IU vitamin D, 1000 IU vitamin D, and 600 IU vitamin D), before which important confounders including sex (boy or girl), body mass index (overweight or obesity), and pubertal stage (pre-puberty and puberty) are determined. Eight strata including 3-blocks of A, B and C (3 intervention groups) are determined (ABC, BCA, CAB, ACB, BAC, CBA). Thus, at the end of the study, the three therapeutic groups in terms of confounding factors, including sex, body mass index, and pubertal stage will be the same and with an equal number of subjects.

in this study participants were aware of dosage of vitamin D supplementation they received. but, the investigator was blind for randomization of participants. so there was no awareness of the dose received by each person.