The Vitamin D study is designed to investigate the effect of body fat mass on vitamin D levels in children. Earlier studies have shown that individuals with increased fat mass may have low vitamin D levels.

Our specific hypothesis states that children with increased fat mass will have lower blood levels of vitamin D when compared to non-obese children.Since vitamin D is the primary hormone for bone mineralization in humans, low levels of vitamin D could lead to decreased bone mineral content in these children.

Fifty prepubertal male and female children of ages between 3-12 years will participate in this study. Of these, 25 obese children will be enrolled in the study group, and 25 non-obese children will serve as controls.

All subjects will fill out a comprehensive mineral intake questionnaire as part of the study to ensure adequate calcium intake prior to the study.

All subjects will collect a first morning urine sample for calcium, creatinine, and NTX.

Fasting blood samples will be drawn for the following analytes: 25-hydroxyvitamin D, 1, 25-dihydroxyvitamin D, intact PTH, calcium, phosphorus, magnesium, osteocalcin, insulin, c-peptide, fasting blood glucose, leptin, and adiponectin.

Bone Mineral Content will be evaluated in 16 obese subjects with vitamin D level of < 30 nmol/L.

Inclusion Criteria:

• General: Prepubertal children (males, with testicular volume of ≤ 3 cc, and girls with Tanner 1 breast) of ages 7-11 years will be enrolled in the study.
• Study group: Subjects with a BMI of > 95th percentile for age and sex.
• Control group: All control subjects will have a BMI of < 85th percentile for age and sex.

Exclusion Criteria:

• known metabolic or genetic diseases resulting in obesity such as severe hypothyroidism, pseudohypoparathyroidism, or Cushing's disease
• diabetes mellitus
• subjects on lipid lowering medications
• subjects on medications known to impact body weight or calcium homeostasis
• subjects with a history of recent significant weight loss or gain

Prepubertal children