From Obesity Panacea:
But wait – could it be that the people who sit more are only at risk because they also happen to be obese? Unfortunately body weight was only available in a subset of individuals in the present study, making this a difficult question to address. However, the authors did examine the association between sitting and mortality after control for body weight in this subset of individuals, and report that sitting remained a significant predictor of mortality. This suggests that all things being equal (body weight, physical activity levels, smoking, alcohol intake, age, and sex) the person who sits more is at a higher risk of death than the person who sits less. The authors go on to suggest that sitting for extended periods of time may alter certain physiological processes, such as lipoprotein lipase activity, which could explain the link between time spent sitting and mortality risk (we’ll get to this in Part 4 of the series!).
I had this conversation over the weekend and the question came up: are people less fit because their obese or are they obese because they’re less fit. That is the kind of chicken-or-egg question that is difficult to answer, but Travis seems to indicate here that the question misses the point because obesity may not be the issue.