Fat, muscle, bone, and television

Article Outline

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It seems that abnormalities in nearly every body system and function have been linked to obesity. Although many of these are likely to be significant, other observations have been difficult to reproduce or associated with many confounding variables. This has been the case for bone mineral density in obese children. Earlier studies have been complicated by differences in activity, pubertal status, body composition, and methodologic concerns.

In the current issue of The Journal, Wosje et al report a study of this association, which appears to address the weaknesses in previous work. A group of over 200 pre-pubertal children were followed serially with measurements of body composition, activity, bone area and mass, and TV viewing. The study design allowed for much better dissection of the contributions of individual variables to bone accrual. The report is complex, with a number of intriguing conclusions. It appears clear that higher fat mass at age 3.5 years is associated with reductions in both bone area and bone mass at 7 years. Even though a higher amount of TV viewing is also negatively associated with bone accrual, this effect appears to be independent of activity. In other words, there appears to be a negative effect of the “inactivity” associated with watching television that is independent of simply cutting into time available for “activity.”

This report provides more ammunition to advocate for obesity prevention and reducing TV exposure. Beyond this, however, it provides a wealth of data upon which additional studies may be based.