What caused the childhood obesity epidemic?

Earlier this year I was asked to give a talk on the childhood obesity epidemic for faculty and staff of the Faculty of Health Sciences at the University of Ontario Institute of Technology (UOIT).  The folks at UOIT were good enough to record the lecture, so I’ve embedded it below (email subscribers can view the video on the blog).

I should note that the video has been edited slightly to remove several “Think-Pair-Share” discussions with the folks attending the lecture.  So if I appear to make some random segues from time to time, that’s why.

The lecture is based on this paper that I published two years ago in the journal ISRN Pediatrics.  I also featured the paper in a 4-part series here on Obesity Panacea, which you can find here.  I should mention that while I focused on Canadian data when possible, the conclusions wouldn’t have been at all different for American kids.  In the paper and lecture I briefly recap historical trends in body weight (FYI – the doubling of childhood obesity rates over the past 30 years are not due to changing the definition of obesity), then look at the most likely causes of those changes.

For a risk factor to be considered a “cause” of the childhood obesity epidemic, two conditions need to be met:

1.  The factor must be shown to promote excess weight gain in childhood

2.  The factor must have increased before/during the childhood obesity epidemic

Based on those criteria, there are 4 factors that we can say (or at least I say) have contributed to the childhood obesity epidemic with relative certainty.  These are:

  1. Sugar sweetened beverages (e.g. pop)
  2. Sedentary behaviour (especially screentime)
  3. Lack of sleep
  4. Adult obesity

People might be surprised that diet and physical activity aren’t on that list.  But really, it comes down to measurement issues.  It is certainly plausible that diet and physical activity contribute to increased childhood obesity rates.  The problem is that the historical data for both of these variables is really weak, and often contradictory.  The data for sugar sweetened beverages and screen time isn’t of much better quality, but the findings for both of those outcomes is much more consistent than for physical activity or diet more generally.

In the lecture and paper I also look at a variety of other risk factors (changes in gut bacteria, reduced breast-feeding, etc), and while there are some interesting findings there, it just isn’t to the point where you can make a strong conclusion with respect to obesity rates at the population level.

Check out the video, look at our previous series on the childhood obesity epidemic, or download the review paper that started all of this (it’s an open access paper, and can be downloaded or viewed online for free).  Also, my sincere thanks to Drs Ellen Vogel and Meghann Lloyd for inviting me to speak at UOIT – I had a great time, and enjoyed the opportunity to see their new campus.





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