Association does not imply causality yet my money says that this morning (I'm writing this yesterday afternoon) the media reports will be awash with the message that rising Canadian obesity rates may well be a consequence of declining Canadian levels of fitness (as evidenced from yesterday's publication of the Canadian Health Measures Survey).
Personally I would argue that if we're looking for causality it's far more likely that obesity has impacted on fitness rather than the other way around given that fitness doesn't burn nearly as many calories as would be fair.
As an example, here's a video from youtube (email subscribers need to head to the blog to view the video) pitting the treadmill vs. a pizza where the participants aim to illustrate why it is, "you can't out train a bad diet".
Ultimately I believe the evidence strongly suggests it has been the world's rising caloric intake that takes the lion's share of responsibility for fueling the global obesity epidemic, not declining fitness.
So looking at the flip side, could obesity impact on fitness levels? Of course. It's more difficult to exercise with more weight, some folks may be embarrassed to exercise due to their weight, while others may have developed co-morbidities that have impacted on their ability or desire to exercise. Less exercise due to excess weight would of course lead to declining levels of physical fitness.
Or maybe fitness and fatness aren't strongly related at all in either direction. The Canadian survey that's reporting declining fitness notes the decline has occurred since 1981. You know what else has happened since 1981? Cable TV, the Internet, XBOXes and instant messaging have all happened - 4 great reasons as to why fitness may be declining and if my assertion that fitness doesn't burn enough calories to dramatically impact on rising rates of obesity is correct then perhaps as far as a discussion surrounding obesity goes, declining physical fitness is more of a red herring having occurred as a consequence of non-obesity related modern age sloth.
Here's my concern. Fitness as a determinant of health is likely second in importance only to diet. My worry is that when personal or societal interventions to improve fitness as a means to combat obesity ultimately disappoint, that people will abandon fitness having forgotten or ignored the importance of fitness for fitness' own sake.
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