Friday, January 21, 2011

Inactivity Does Not Explain Canada’s Obesity Epidemic

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.

AMS
Guelph, Ontario

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20 Responses to “Inactivity Does Not Explain Canada’s Obesity Epidemic”

  1. Yoni Freedhoff says:

    Great article Arya!

    My only complaint is that you beat me to the punch. Will now have to scrap the extremely similar piece I was halfway through for Monday’s blog!

  2. Paul Boisvert says:

    Arya, I am surprised … by your surprise and misinterpretation. When you say “overweight and obese kids and adults are only marginally (if at all) less active than their “normal” weight , the differences in actual minutes was rather modest” I am not agree. Overweight and obese and mostly HALF active than normal weight, which is important because it is nearly 50% of the recommend 30min of moderate activity: ” 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” In fact, bith normal weight and obese are not active enough

  3. Richard says:

    Is there any real solution for weight loss or all companies behind my wallet? I have tried many products for weight loss, but none, none has given me any results. Can someone help me with a solution on this please?

  4. NewMe says:

    Dr. Sharma: This is a brilliant article. Would that more people had enough sense to understand it. The world seems to be filled with fat haters, who blithely assume that every extra pound is simply due to slothfulness and greedy overeating.

  5. Margaret Sharpe says:

    You’re my hero!

  6. Twitter Trackbacks for Inactivity Does Not Explain Canada’s Obesity Epidemic | Dr. Sharma's Obesity Notes [drsharma.ca] on Topsy.com says:

    [...] Inactivity Does Not Explain Canada’s Obesity Epidemic | Dr. Sharma’s Obesity Notes drsharma.ca/inactivity-does-not-explain-canadas-obesity-epidemic.html – view page – cached 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 [...]

  7. Arya M. Sharma, MD says:

    @ Yoni: :) (but still would like to read your post on this)

    @Paul: You are right – ALL Canadians are inactive and need to do more. I just don’t think that if you look at activity levels as work done or calories burnt that there is much difference between “normal”, overweight, or obese Canadians – hence my comments.

  8. Travis says:

    Arya,

    Very interesting post! One point I’m hoping you can clarify:

    You have argued in the past (I think) that obesity levels are plateauing, and that in general, those who are susceptible to obesity are now obese, while those who are not susceptible remain lean. Doesn’t this argument imply that everyone, regardless of body weight, is not exposed to more or less the same environment (within reason of course)? If that’s the case, then I’m wondering if we’d expect to see differences in PA between lean and obese kids at present, since the differences in body weight could have more to do with their susceptibility to obesity than anything else, given that their actual behaviours are relatively homogeneous (for example, the sedentary behaviour is very homogenous at the moment, making it pretty difficult to tease anything out).

    The fact that there is no difference between lean and obese kids now, when physical activity levels are likely at historical lows, and sedentary levels are at historic highs, doesn’t seem as important in determining the etiology of the obesity epidemic as the historic trends in these variables (of which the data is pretty weak, but no weaker than diet).

    I’m not saying that exercise is driving the boat on this, but I’m skeptical about the amount we can really read into this one x-sectional paper.

    Travis

  9. Arya M. Sharma, MD says:

    @Travis: 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.

    I would have liked to see a clear statement both in the abstract and in the discussion of these findings emphasising for the reader that these finding DO NOT show that overweight and obese individuals are any less active than “normal” weight individuals.

    I see this as a missed opportunity to correct that stereotype, which for all the reasons we heard at the recent Weight Bias Summit, are extremely counterproductive and hurtful.

    BTW, you are right with regard to eating – I am sure that if we had exact numbers on this and corrected for socio-economic class and other factors, we would probably find that overweight and obese people on average are NOT eating more junk food, drinking more pop, or eating fewer fruits and vegetables (my guess is that their diets are no better or worse than everyone elses diets).

    Here again one needs to make adjustments for the higher energy requirements of obese individuals – at a stable weight larger people need more calories because they are larger so simply saying obese people eat more (even if this was the case) without correcting for their increased requirements would also be a wrong conclusion.

  10. Travis says:

    Thanks for the clarification!

  11. Weekend Wrap Up – sound bites that caught my eye | Wellness Nutrition says:

    [...] never supported by science. Dr Ayra M Sharma, one of Canada’s obesity experts, explains here. For a more in-depth review of the role of exercise, check out this post by Lyle McDonald on the [...]

  12. Time to sever the link between inactivity crisis and obesity epidemic? | Obesity Panacea says:

    [...] 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 [...]

  13. Jetske says:

    Excellent article. I wonder what the differences would be if activity was measured not in terms of “accelerometry” but actual exertion. I’ve read that Heart Rate is the best predictor of effort and calories burned during exercise. I, for one, can get a pretty good heart rate going simply by hauling my 228 pounds up a hill at a walk. Perhaps a thinner person would have to move a lot quicker to attain the same heart rate (and expend the same amount of energy).

  14. AllieL says:

    Dr. Sharma,

    You make some very interesting points in your notes. I am just curious then, what do you think contributes to the obesity epidemic in Canada, the US, Italy, Australia…..??
    I do agree that it is not just those who are considered as overweight or obese not engaging in physical activity, but I do think that physical inactivity is a component to their condition. Like you point out, their weight creates more work for them. They may suffer from back problems, arthritis, depression, asthma and exertional dyspnea, but what came first, the chicken or the egg?
    Whether nature or nurture or both, there are many predisposing factors to obesity.
    The resolution, in my eye, lies within primary prevention, and this begins early.

    Childhood obesity is a strong predictor of adult obesity. G Plourde in 2006 (Canadian Family Physician) reveals that 33% of obese preschool children remain obese as adults and therefore there is a need to focus preventative measures on young children.
    Lobstein, Baur and Uauy (2004) reveal the most wanted topic for continuing eduction in the USA is pediatric obesity. This finding has resulted in a number of published practice guidelines, but again many studies reveal that primary care providers do not follow the guidelines. The majority of excuses for not using the guidelines are: lack of time and a sense of discomfort/lack of confidence in speaking to parents about their child being at risk for or being overweight.
    We need to stop making excuses and move forward, educating parents about the risks of childhood obesity, contributing factors, and provide resources to the individual barriers that are identified in the interview.
    And lets face it, it is not difficult to see what contributes to this epidemic: the majority of Canadians work very hard, we run out of time and energy to take care of ourselves – we eat convenient food, skip the gym, feed the kids, clean the house and back to work.
    The Ontario Medical Association (2009) reveals that obesity costs Ontario 2.2-2.5 billion dollars each year (direct and indirect costs).
    Something needs to be done!

  15. Fei says:

    So are you saying that we do not need to exercise?

  16. Arya M. Sharma, MD says:

    @Fei: no, I am saying everyone needs to exercise, thin, fat, young, old, male, female, everyone!

  17. Fivehundredpoundpeep says:

    I have my theories about the obesity epidemic that I have written on. I am even wondering about the extreme amounts of MSG that is being poured into our food–almost every processed item has it. I was in shock, when I learned that it is a known FACT that rats are fattened up purposefully with MSG, well what is happening to the population when all the food except cook from scratch items is full of this stuff?

    http://fivehundredpoundpeeps.blogspot.com/2011/10/msg-is-used-to-make-lab-rats-fat-how.htm

    Years ago I wrote this article too about the causes of the obesity epidemic.

    http://victoria682.tripod.com/thelargestofall/id1.html

    Something is happening to people’s bodies, beyond just calories in calories out, and failed will-power.

  18. Fivehundredpoundpeep says:

    fixing link on top that doesn’t work above…

    http://fivehundredpoundpeeps.blogspot.com/2011/10/msg-is-used-to-make-lab-rats-fat-how.html

  19. Dawn says:

    The low fat/high carb, insulin increasing diet that has been pushed for the last half century is the real cause of obesity. Ansel Keys 7 country study, which called diet fat the cause of heart problems, in fact had 22 countries. He threw out every country that did not support his ideas. In fact the increase in sugar and grains in the diet were the cause of heart problems.
    As a result of this, even though there was never any evidence to support it, a low fat/high carb diet has been recommended. The same diet used to fatten livestock. Also we have switched away from real fats to chemially produced vegetable fats that no one should be eating. The result of this diet has been increased obesity, heart attacks, strokes, diabetics, depression, AdHd in children and infertility.
    However, there are economic reasons for many of the so called experts to keep recommending the low fat/high carb death diet. It is time to put the health of Canadians ahead of the economic interests of a few people.
    While there are some people who can do well on a low fat diet, the same as there are some people who can smoke heavy and drink all their lives, it is not a healthy diet in any way.

  20. Physical Activity: From Genes to Policy | Dr. Sharma's Obesity Notes says:

    [...] the direction of this relationship (remember, the Canadian Measurement Survey found little association between activity levels and BMI in both kids and adults), this paper [...]

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