Childhood obesity: Solution is not ‘eat less, move more’
By Dr. Arya M. Sharma
One of the common misconceptions around the obesity epidemic is that kids with excess weight have lifestyles that are much less healthy than those of their non-obese peers.
It’s a familiar assumption that professionals, policy makers and the average person often make. The truth is, this assumption is not borne out by data. A report from the Canadian Health Measures Survey 2007-2009 (released by Statistics Canada early this year) found no marked differences in physical activity between overweight and lean kids, at least not when corrected for the increased effort it takes to move larger bodies. 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.
Specifically, overweight and obese girls aged six to 19 years had exactly the same minutes of moderate-to-vigorous physical activity (MVPA) as girls who are neither overweight nor obese (between 44 and 48 minutes per day). Only for boys was there a discernible relationship between activity and BMI, in that overweight boys had 14 minutes and obese boys had 22 minutes less daily activity than “normal” weight boys, who accumulated around 65 minutes of MVPA per day.
So, if overweight kids are not moving less — and if, as other data suggest, they are not necessarily eating more — why are some kids overweight and others not? If the environmental effects are pretty much the same for everyone, why do we even have lean and obese kids?
This question was addressed by researchers from the Ludwig-Maximilians University of Munich, Germany, in a study published in PLoS One this past January. The authors analyzed data on over 7,000 three- to 10-year-olds and almost 6,000 11- to 17-yearold children from a representative cross-sectional German health survey conducted between 2003 and 2006. The goal was to look at the impact of maternal BMI, maternal smoking in pregnancy, low parental socioeconomic status, exclusive formula-feeding and high TV viewing time on BMI.
It turns out that in both age groups, the estimated effects of all risk factors (except formula-feeding) on BMI were greatest for children with the highest BMI. In other words, it is not that lean kids don’t also watch a lot of TV or have mothers who smoked during pregnancy — rather, it’s that kids at the higher end of the BMI distribution appear far more sensitive to these factors than their leaner counterparts.
Thus, kids who are genetically predisposed to obesity are far more likely to pack on the pounds when spending hours in front of the TV than kids who are genetically less obesity prone. The same could probably be said for overeating or any of the other environmental drivers of obesity, which have much greater effects in terms of promoting weight gain in some kids than in others.
From a prevention and treatment perspective, this means that overweight and obese kids will have to work much harder at changing their lifestyles or avoiding obesogenic stimuli than thin kids, who can live a similar lifestyle without negative health consequences. It’s easy to see how this relates back to the topic of weight-bias and discrimination, where we so easily fall into the mode of blaming obesity largely on unhealthy lifestyles and will power, when thin people may just turn out to be genetically more fortunate.
This should not, of course, be used as an excuse to do nothing. Rather, it should be seen as a good reason to fully appreciate and empathize with kids who carry extra weight. Some will need to work very hard at controlling their weight, while others seem to have simply drawn the “get out of jail free” card.
In light of these data and the tremendous negative emotional and physical impact of weight bias, discussing inactivity (or exercise) in the context of obesity is not only obfuscating the real issues, but it’s 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 recognized health risks associated with sedentariness.
Similarly, we know that increasing physical activity and sensible exercise “prescriptions” can be important prevention and treatment strategies for weight management.
It is, however, high time 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), it may well do more harm than good when it comes to tackling both the epidemic of obesity and the epidemic of sedentariness.