Inactivity Does Not Explain Canada’s Obesity EpidemicFriday, January 21, 2011
This week, Statistics Canada released the latest horrifying report on the state of physical activity in Canada. The findings from the 2007-2009 Canadian Health Measures Survey, show that neither kids nor adults come anywhere close to meeting even the most modest recommendations for daily physical activity.
Thus, based on actual measurements of physical activity using sophisticated accelerometric devices, only 5% of Canadian adults and children meet the recommended levels for vigorous physical activity per week.
And now comes the surprise: overweight and obese kids and adults are only marginally (if at all) less active than their “normal” weight counterparts.
Specifically, overweight and obese girls aged 6 to 19 years have exactly the same mins of moderate-to-vigorous physical activity (MVPA) as girls who are neither overweight or obese (between 44 and 48 mins per day). Only for boys is there a discernible relationship between activity and BMI in that overweight boys have 14 mins and obese boys have 22 mins less of daily activity than “normal” weight boys, who accumulate around 65 mins of MVPA per day.
In adults, likewise, there was an apparent relationship between MVPA and BMI levels, but the differences in actual minutes was rather modest.
Overweight men aged 20 to 79 accumulate 9 mins less of MVPA per day and obese men accumulate 16 mins less of MVPA per day than the 35 mins measured in “normal” weight men.
Overweight women aged 20 to 79 accumulate 5 mins less of MVPA per day and obese women accumulate 12 mins less of MVPA per day than the 25 mins measured in “normal” weight women.
Although the casual observer may look at these numbers and conclude that yes indeed overweight and obese individuals are (albeit modestly) less active than “normal” weight folks, this conclusion would be plain wrong.
Firstly, accelerometers measure acceleration or intensity of movement (which is translated into steps), but step-for-step moving a heavier body mass requires more effort and work. Therefore, simply looking at the number of daily mins or steps without correcting for the extra weight that is being moved, is simply misrepresentation of the actual work done. Rather, I would actually interpret these findings as demonstrating that overweight and obese Canadians are as, if not more, physically active than the skinny folk, who effortlessly clock in their seemingly higher numbers. (In fact, I would for once love to see the buff personal trainers in Village on a Diet put on 200 lb “fat suits” and run up the hill in Taylor – I would not be surprised if they had to stop for a quick vomit half way up the hill).
Secondly, these data do not provide any insight into causality or consequences. Thus, for example, many of the overweight and obese adults may well have physical and/or mental health issues that make MVPA so much more difficult: back pain, arthritis, sleep apnea, depression, asthma, exertional dyspnoe, etc. So looking at averages in this population, without taking into account that many overweight and obese individuals would need to struggle far harder than their “normal” weight counterparts to achieve the same number of mins or steps, may actually underestimate the fact that many overweight and obese individuals may well beat their skinny counterparts handsdown in terms of physical activity.
While in kids, medical reasons for the marginally lower MVPA may not be relevant, mental health and emotional issues like self-esteem, body image, weight-based bullying, and discrimination may be important barriers to putting in as many minutes of MVPA as their “normal” weight counterparts. As these factors traditionally are a much greater deterrent to physical activity in girls than in boys, I am in fact amazed, that overweight and obese girls are as active (while actually doing more work because of the extra pounds that they carry around) as their “normal” weight peers.
Thirdly, 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.
Indeed, it is exactly the reporting of these kind of data in the context of obesity, that serve only to reinforce stereotypes: obese people are obese because they are lazy and a good kick in the butt will solve the obesity epidemic.
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.