Consistently watching high levels of television during childhood and adolescence were linked with lower peak bone mass at age 20 years in a recent study.

In the Journal of Bone and Mineral Research study, hours of television watching per week were recorded by parental or self-report at 5, 8, 10, 14, 17 and 20 years of age in 1181 participants. Those who consistently watched ≥14 hours/week of television had lower bone mineral content than those who watched less television, even after adjusting for height, body mass, physical activity, calcium intake, vitamin D levels, alcohol, and smoking (all at age 20).

"Since attainment of optimal peak bone mass is protective against osteoporosis later in life, reducing sedentary time in children may have long-term skeletal benefits," the authors wrote.

Article: Longitudinal Trajectories of Television Watching Across Childhood and Adolescence Predict Bone Mass at Age 20 Years in the Raine Study, Joanne A McVeigh, Kun Zhu, Jenny Mountain, Craig E Pennell, Stephen J Lye, John P Walsh and Leon M Straker, Journal of Bone and Mineral Research, doi: 10.1002/jbmr.2890, published online 4 July 2016.