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Unexplained Variance of Obesity Levels Across Canada



As in most countries, the population levels of obesity in Canada vary considerably from province to province (as they do within provinces). Although there are many “theories” on why this may be the case there has been little work done on trying to unravel the “explained” and “unexplained” regional variation based on a comparison of factors known to affect obesity levels such as socio-economic status, urban-rural distribution, and other variables.

This issue was now addressed by Daniel Dutton and Lindsay McLaren from the University of Calgary, Alberta, in a paper just published in OBESITY.

Using data from the nationally representative Canadian Community Health Survey (CCHS) (2004), the researchers attempted to decompose the difference in mean BMI between regions, into differences explained by different levels of the covariates between regions and a share explained by those covariates having different effects on BMI in the different regions.

Canada was split into five regions for this analysis: British Columbia, the Prairies (Alberta, Saskatchewan, and Manitoba), Ontario, Quebec, and the Atlantic provinces (Nova Scotia, New Brunswick, Prince Edward Island, and Newfoundland). The Atlantic provinces, which currently have the highest obesity rates in Canada, were used as the reference group.

While some differences between provinces (e.g., average BMI for males in Quebec compared to the Atlantic provinces) are mostly explained by the different levels of socio-demographic and behavioral covariates, others (e.g., average BMI for females in Quebec compared to the Atlantic provinces) are mostly explained by the different effects of the covariates on BMI.

One example of a surprising difference between regions is that the impact of increased fruit and vegetable consumption on BMI is substantially stronger in Ontario and Quebec women than in Atlantic women.

The authors have the following explanation to offer regarding this finding:

“One possibility is that the quality of fruits and vegetables consumed differs by region. For example, fruit servings in the Atlantic provinces may consist of more canned fruits (due to a climate less conducive to growing a variety of fruits or geographical distance affecting the efficiency of transporting perishables to the region), which are often packed in syrup, adding to the calorie count, compared to fresh fruits. Another plausible explanation is that consumption of other foods varies regionally, and differentially offsets the impact of fruit and vegetable consumption. For example, if high levels of consumption of fruits and vegetables in the Atlantic region are associated with higher consumption of food overall (including less healthy foods), perhaps reflecting dietary social norms, then we would observe different returns to the consumption of fruits and vegetables.”

Thus, even if covariates (e.g. promoting the consumption of fruit and vegetables) were made to be identical in the different regions, the difference in average BMI between regions would still persist.

As the authors note:

“Thus, targeting covariates in different regions through plans like physical activity or nutrition policy, income equalization, or education subsidies will have ambiguous effects for addressing disparate obesity levels, being plausible policy options in some regions but less so in others.”

Therefore, while some drivers of obesity may best be addressed by federal policies, each region may have to adopt their own strategies to fully address the obesity problem – what works well in one province may have little to no effect in others.

It appears that what applies in clinical practice, also applies for efforts at the regional level: one size does not fit all.

AMS
Edmonton, Alberta

Dutton DJ, & McLaren L (2011). Explained and Unexplained Regional Variation in Canadian Obesity Prevalence. Obesity (Silver Spring, Md.) PMID: 21253004

4 Comments

  1. Consider culture.

    1. What is a healthy weight?
    Growing up in 1950’s Newfoundland:
    My mother thought ordinary kids were too skinny. She equated “chubby” with “healthy”.
    (Maybe from thinness being associated with malnutrition and TB in the old Nfld remote outport of her parents.)

    Suggested study: Get photos of individuals ranging in size from very thin to very obese, for groups of same sex and age.
    Get people to pick out photo from each group which shows a healthy weight. Then compare answers from different areas of the country. Do people from different places see different weights as healthy?

    2. The idea that everybody NEEDS and DESERVES food “treats” (treat as in high cal, low nutrient food, often junk food)

    In the mall, my friend giving junk food to her obviously overweight child, saying, “You’re such a good boy, you get a treat” ???
    My roommate in hospital, very obese, on precise diet. Her family brings her snacks. “Just a little won’t hurt, and she needs a treat, it’s so hard for her” ???

    The common threads in many more examples:
    – denial that the treat food will actually have an effect on the body,
    – thinking that if you’re good, you SHOULD have food treats, (if you’re being good and you don’t get a treat, that’s really unfair)
    – thinking that if you’re having problems you SHOULD have food treats,
    – thinking that going without treats is a tragic undeserved hardship.

    I don’t know how to check the prevalence of such ideas in a culture, but probably a psychologist could devise a study. Maybe these ideas, which would affect diet and weight, are more common in the culture of areas of the country with high obesity rates.

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  2. Hi there,

    COULD THE CLIMATE EFFECT THE VARIANCE OF OBESITY LEVELS ACROSS CANADA?

    I moved to Edmonton from Kamloops, BC in 2005. In my six years of living here, I have noticed that there seems to be a lot more obese people here than there were in BC. I have pondered on why this might be and have often thought that it may have something to do with the length of the winter season here.

    Getting physical exercise over the winter is difficult here. The bike riding season is quite short and other than in the “construction” season, the sidewalks are often treacherous for walking outdoors. If you suffer from any mobility problems this year has been especially difficult. And, with the shorter days and lack of light, there also seems to be a tendency towards holding up indoors where it is cozy and warm.

    Going to fitness facilities is an option, but it is expensive and difficult unless you have a vehicle to get there. Walking in the malls is a good option but the roads have been so bad that it is wiser to stay at home. Home exercise equipment is another option, however, many individuals are on fixed budgets and that is not an option. To get enough exercise in this climate, you have to make it a priority in your life and make a real effort to get it done.

    On taking another look at the map, I see the most populated areas in BC have moderate weather, i.e. Vancouver and Victoria. I also note that Kamloops, Kelowna, Penticton, Nelson, Vernon, Salmon Arm, etc., all have fairly moderate climates. They all have four distinct seasons, three of which it is easy to get outdoors for many activities. Is it a coincidence that they have one of the lowest obesity rates in Canada?

    Looking across to Alberta and Saskatchewan, the most populous regions are colder climates, making winters difficult to exercise in. Alberta is in the mid range for obesity. Saskatchewan has an even higher obesity rate and I suspect the weather has a lot to do with it there too.

    I think a study on what the effects of climate have on the obesity rates could quite possibly be very revealing.

    Thanks for listening,

    Rosemary Dinsdale

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  3. Obesity is highly heritable. They should have looked at differences in ethnic makeup.

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  4. recently moved to northern nb. have noticed a large portion of the population here could be termed ‘morbidly obese’ especially young women under 30. also, an abnormally large portion of the population smoke cigarettes, casting refuse everywhere. in fact, to enter a retail establishment here, it is necessary to pass through a thick cloud of cigarette smoke! what happened to the laws? does no one obey or enforce them. I thought smoking was banned within 15 ft of the entrance to a public establishment? not here! even though there is high unemployment in the region, doesn’t seem to cut down of the consumption of tobacco and alchohol.
    what gives?

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