The important caveat in this study was that the results were based on questionnaires, as opposed to objective observation, but the findings are interesting.

Many parents think they’re setting a positive role model for their teens by exercising and staying fit, but the kids don’t seem to care, a study in the Journal of Adolescent Health suggests. . . . The study found there was little correlation between teens’ fitness levels and whether the teens had one or both parents who regularly engaged in physical activity.
Having a normal-weight father or a mother who was physically active on a regular basis didn’t significantly influence adolescent fitness, the study found. Physically active siblings also had little effect on teen fitness.

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