Wednesday, June 30, 2010

Apparently now clumsiness causes childhood obesity.

Only it's not called clumsiness, it's called, "developmental coordination disorder" (DCD) and it reportedly is found in 5-6% of school aged children and according to the authors of a study published this week in the Canadian Medical Association Journal, kids with DCD are at higher risk of overweight and obesity.

The study looked at 2083 children of whom 111 were deemed to suffer from DCD (excluding kids who had physical or mental illnesses).

At baseline the Grade 4 DCD kids were already behind the eight ball having 15% higher mean BMIs and 13% higher waist circumferences than their coordinated peers - a trend that grew through Grade 6.

While this study certainly does seem to draw a strong correlation between clumsiness and obesity these findings can't even remotely be construed as meaning DCD kids' lack of exercise is the cause of the increase in risk - especially given the authors didn't measure how much any of the kids were exercising. Of course that didn't stop the authors from making that stretch in their abstract's introductory statement,

"Children with developmental coordination disorder have been found to be less likely to participate in physical activities and therefore may be at increased risk of overweight and obesity."
A statement which when considering the study is meant to determine whether or not DCD is associated with increased obesity risk certainly lends literary (not evidentiary) credence to the notion it's due to these kids' decreased activity levels.

So what else might be going on with here? Off the top of my head here are 3 other potential clumsy weight related confounders:

1. Perhaps the DCD kids drown their uncoordinated sorrows in a few extra Big Gulps every week. While that may seem trite, if the theory is that these kids aren't playing organized or even playground sports certainly it's plausible that they might eat more during their extra free time and may as well be more likely to be comforting themselves with food.

2. Perhaps the DCD kids are kids who come from less nurturing or less privileged homes where their parents may not have had the time, inclination or funds to support things like dance lessons, soccer camps or simple let play together time leading to lesser motor developments. In turn those same homes may well have different dietary and social environments that could account for the differences found herein.

3. Perhaps as my friend and colleague Arya Sharma suggested in his blog yesterday, it's the overweight and obesity that causes DCD rather than the other way around.

And I'd argue that one of those options is far more likely to be causal than a lack of exercise as frankly the amount of exercise that would need to be accrued by age 10 to account for such a significant difference in body weight would be truly phenomenal especially given the fact that other studies have found that even a ten fold difference in childhood exercise didn't impact on body weight.

Ultimately this is an interesting study with interesting results, I just wish it wasn't painted with the all too common exercise is the cure-all and cause-all for childhood obesity brush as I think it's much more likely that obesity leads to clumsiness rather than the other way around and likelier still that there's something else in the mix that's not being accounted for here.

Hopefully the next round of studies on these kids will either help elucidate a more plausible mechanism for the association or prove me dead wrong in that indeed it's all about exercise - either way, I'll be sure to blog about it.

Cairney, J., Hay, J., Veldhuizen, S., Missiuna, C., Mahlberg, N., & Faught, B. (2010). Trajectories of relative weight and waist circumference among children with and without developmental coordination disorder Canadian Medical Association Journal DOI: 10.1503/cmaj.091454