Building stronger bones during pubertal growth could reduce lifelong fracture risk. This project is an 18 month dairy intervention study for overweight and healthy weight 4th-8th grade boys and girls. Half of the girls will receive dairy products to add to their habitual diet (milk, yogurt, and cheese) to equal three products per day, while the other half will remain on their normal diet. All participants will attend four study visits, each 6 months apart. At these visits height, weight, bone density and geometry, and fat and lean mass will be measured. This study aims to show that meeting calcium requirements by eating dairy products builds bigger, stronger bones, and that this effect may be enhanced in overweight boys and girls. The effect of the dairy intervention on body fat, lean mass, and weight, as well as the mechanisms and predictors of changes in bone mass and size and body composition will also be evaluated.

Inclusion Criteria:

• Males and females in 4th-8th grade
• Generally healthy
• BMI percentile 5-70% for age or >85% for age
• Baseline calcium intake less than or equal to 800mg/d

Exclusion Criteria:

• History of any illness known to affect bone mass accrual (diabetes, inflammatory bowel disease, childhood malignancy).
• A broken bone in the last six months.
• Consume more than 800 mg Calcium/d.