Adiposity and TV Viewing Are Related to Less Bone Accrual in Young Children

Objective To examine the relation between baseline fat mass and gain in bone area and bone mass in preschoolers studied prospectively for 4 years. with a focus on the role of physical activity and TV viewing. Study design Children were part of a longitudinal study in which measures of fat, lean and bone mass, height, weight, activity. and diet were taken every 4 months from ages 3 to 7 years. Activity was measured by accelerometer and TV viewing by parent checklist. We included 214 children with total body dual energy x-ray absorptiometry (Hologic 4500A) scans at ages 3.5 and 7 years. Results Higher baseline fat mass was associated with smaller increases in bone area and bone mass over the next 3.5 years (P < .001). More TV viewing was related to smaller gains in bone area and bone mass accounting for race, sex, and height. Activity by accelerometer was not associated with bone gains. Conclusions Adiposity and TV viewing are related to less bone accrual in preschoolers. (J Pediatr 2009,154:79-85)