Time to sever the link between inactivity crisis and obesity epidemic?

Two weeks ago our colleague Dr Arya Sharma published a very interesting post discussing the latest reports on the extremely low levels of physical activity in the Canadian population (sometimes referred to as the “inactivity crisis”).  The gist of the reports are that exceedingly few Canadians (7% of kids and 15% of adults) are meeting physical activity guidelines.  But Dr Sharma’s argument is that although most age groups showed a relationship between BMI and physical activity level (e.g. lean boys tended to be more active than obese boys), the real take-home message is that physical activity levels are low in all groups, not just among those who are overweight and obese.  From Dr Sharma (it’s a great post, so please do visit his site to read the whole piece):

…if we convert the rather modest differences in MVPA levels taking into account the increased effort required to move higher body weights, we would find almost no difference in actual calories spent in activities to account for any difference in body weights.Thus, to me at least, these data pretty much blow to pieces the widely held bias that overweight and obesity can be largely explained by lack of activity or that overweight and obese individuals are less physically active (read “lazy”) than “normal” weight individuals.

In light of these data and the tremendous negative emotional and physical impact of weight bias, I stongly believe that discussing inactivity (or exercise) in the context of obesity is not only obfuscating the issues but also a major distraction from addressing the real causes of the problem.

This should in no way imply that the shockingly low activity levels of ALL Canadians (young and old, male and female, slender and obese) should not be cause for alarm given the innumerable health benefits of physical activity and the increasingly recognised health risks associated with sedentariness. In addition, these comments should also in no way imply that increasing physical activity and sensible exercise “prescriptions” are not important prevention or treatment strategies for weight management.

It is, however, hightime to reframe the discussion of inactivity and sedentariness as a discussion about fitness and health risk in general rather than as a discussion on obesity.

Continuing to link the necessary discussion about inactivity to the problem of obesity is not only scientifically unfounded but, by dangerously and unfairly reinforcing stereotypes (not reflected in the actual data), may well do more harm than good when it comes to tackling both the epidemic of obesity and the epidemic of sedentariness.

Now this is not to say that reduced physical activity levels don’t play a role in the obesity epidemic, nor that they are not an important player in weight maintenance.  Again, from Dr Sharma (this time in the comments section):

…absolutely, it is well possible that the overall reduction in physical activity may play some role in the right shift in the bell curve of weight distributions, and getting everyone moving more may eventually lead to a left shift of this distribution (although I am not holding my breath on this one).My issues are not with whether or not activity is important for health or to reduce the risk of obesity.

My issues are solely with the misrepresentation of these findings as reinforcing the stereotype that overweight and obese people are less physically active, when in fact they may well be expending more effort (and calories) than their “normal” weight counterparts.

All of this brings us back to our recent discussion of problematic obesity-related public service announcements.  Because, as you might expect, it’s commonplace for public health messages to make an implicit or explicit link between the inactivity crisis and obesity epidemic. It’s hard not to – obesity is negatively associated with physical activity, and if you’re trying to make a case for why people should be more active, it’s a pretty easy way to get their attention.

Even ParticipACTION, Canada’s standard-bearer for physical activity, has gone down this route on occasion.  For example, their video titled “There is a crisis in Canada” (unfortunately I can’t embed it, but it’s the 4th video down on this page) starts with various shots of headless obese individuals, while the voice-over states “There is a crisis in Canada.  A crisis of epic proportions.  Canadians are simply not moving enoughNearly half of the adults in this country are overweight or obese.” Now those statements are undoubtedly true, but putting them together like that seems to imply that obese individuals are obese simply because they don’t move enough, and that moving more would solve the problem.

Why does this all matter?

In addition to the issue of weight bias discussed by Dr Sharma, I think that it also sets up unrealistic expectations for people about the impact of physical activity.  Yes, if all Canadians were physically active we would likely weigh less as a nation.  But the average weight loss in response to a moderate increase in physical activity levels is very modest, and it’s likely that many people would see no weight reduction of any kind.   Even if it’s in the range of 5% of body weight (which is unlikely over the long-term), it’s probably substantially less than most people are hoping for. In which case the individuals who are only exercising for the sake of losing weight are going to get discouraged pretty quickly (Peter has written a few excellent reviews on this topic with our former supervisor Bob Ross, and I’d recommend this one, titled “Is weight loss the optimal target for obesity-related cardiovascular disease risk reduction?“).  Further, this overwhelming focus on the relationship between inactivity and obesity may lead some lean individuals to conclude that they have no reason to be physically active since their body weight is already in a normal range.

This is a shame because exercise is associated with myriad health benefits, regardless of an individual’s body weight.  In fact, a single session of aerobic exercise results in measurable improvements triglyceride levels, HDL (good) cholesterol, and insulin sensitivity, even though it has no real impact on adiposity.   Further, it has been noted that mortality levels are lower among obese but fit individuals, as compared to lean but unfit individuals, suggesting that we really do need to be promoting physical activity as a healthy behaviour for everyone, not just those who are overweight or obese.

So what strategy should we adopt instead?  I would argue that a good example is ParticipACTION’s new campaign, titled Think Again.  In contrast to the video I discussed above, the “Think Again” ads are funny (and less terrifying) and get the point across that physical activity needs to be an everyday occurrence for all children, without any mention of obesity.  Actually, aside from the “crisis” video, most of their other ads are very good (which I could illustrate if the videos could be embedded on other web sites…), and I especially enjoy the “inactive kids get old before their time” series at the bottom of this page.

As I’ve argued in the past, I think that any public health campaign would do well to focus on the behaviours that we want to promote (e.g. less sitting, more activity), rather than the outcomes that we have less direct control over (e.g. obesity, diabetes, heart disease, etc).  I know that’s not always as media-friendly as obesity, but I think it has a better chance of making a positive long-term impact.

So what do people think – is it time for us to sever the link between the inactivity crisis and the obesity epidemic?


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