Tuesday, August 19, 2008

Obesity is Still not about Exercise!

You need more proof that we're not going to put a dent in childhood obesity with exercise?


Published ahead of print in the Archives of Diseases of Childhood is a simple study that looked at 300 children from 54 different schools in the city of Plymouth in the UK.

Dr. Brad Metcalf et al. followed the children for 4 years (from the age of 5 to 8) and looked for associations between the variables of physical activity, body mass index, body fat percentage and some metabolic blood parameters.

Guess what?

There was no association found between the amount the children exercised and their body mass indices or body-fat percentages over time despite the fact that amongst the children there was a ten fold difference in the amount of physical activity that did not in fact change over the course of the study.

That finding is so powerful I'm going to rewrite it big and bold:

Despite the fact that some kids were ten times more active than their peers, their 4 year long, ten-fold increase in exercise did not help them maintain healthier body weights or body fat percentages!
The exercise wasn't all for naught however as metabolic parameters were in fact better in the exercisers.

I wonder how many more studies need to come out before it becomes mainstream to know that exercise as a component of obesity is minor at best?

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  1. Hi, I have been doing a lot of reading lately and I am curious if you have a stance on the Weston A. Price Foundation?

    I'm more interested in your opinion on the health benefits than whether it would contribute to obesity or not. Specifically regarding saturated fats verses vegetable oils. All of this info starts to get really confusing for someone who is not a professional dietician!

  2. Hi Josephine,

    Sorry, not familiar with the Foundation you mentioned.

    Regarding saturated fats vs. vegetable oils. Certainly there's a tremendous amount of research that suggests saturated fats contribute poorly to bad cholesterol, but that said, there is also a tremendous amount of research that suggests maximizing your unsaturated fats has more health benefits than minimizing the saturated ones.


  3. Yoni, I think the fundamental flaw in this and other posts like it from you is the assumption you seem to have that there is a magic bullet solution to a single cause for childhood obesity that we haven't discovered yet.

    There are probably dozens if not hundreds of contributing factors that have caused kids to get fat recently, as compared to a few decades ago.

    Fixing one factor (like the lack of exercise) is not going to do it or even have a perceptible effect. But at some point when enough things are changed there will be a tipping point. But we have to do things one by one and keep our eyes on the details.

    The biggest problem and the hardest to fix is that most children have fat parents today. That is a really overwhelming piece of environmental/lifestyle influence to deal with, but there's not a lot we can do about it. The parents aren't going to get skinnier and are not going to start eating less, and kids are subjected to that day in and day out in their formative years.

  4. Another way to look at this really would be to say, "wow, exercise helps make fat kids healthier" rather than "oh no, exercise doesn't make fat kids thin."
    We can't tell which of the fat kids would be fat no matter how much exercise and how few calories they consumed. So at the least, making sure that all kids can be active helps keep all kids healthier, regardless of weight.

    Even if there are more fat kids today than there were before, it's not as though the prevalence of childhood obesity used to be zero.

    We may not know how to reverse the trends, but we do know that developing a lifelong love for physical activity, regardless of size, along with less stigmatization, will only produce healthier people.

  5. Wellrounded,

    You're absolutely right.

    As I've posted many times, exercise as a determinant of health is unquestionably important.

    Unfortunately public health agencies, schools, the general public etc. are stuck on exercise as a means to treat or prevent obesity (usually specific to childhood obesity). Since the data clearly demonstrate that exercise does not prevent or treat obesity in children, clarion calls for more gym class as a means to treat obesity become risky.

    It's risky for two reasons. Firstly presumably if such programs are established success will be measured by weight. Given that weight's unlikely to change as a consequence, these interventions which you rightly point out will improve health will be abandoned.

    Secondly it's risky because if someone is able to tap into some dollars to actually address the issue of childhood obesity through the establishment of exercise programs (ParticipACTION leaps to mind), then that money will no longer be available for interventions that may actually make a difference.

    Bottom line. I'm exceedingly pro-exercise and think the benefits of exercise are worthy of funding all by themselves. I'm exceedingly leery however of promoting exercise as a means to combat obesity.

  6. Thanks for you reply... I know we are on the same page on this, but sometimes language skews things.

    Which is why I strongly advocate for measuring things other than obesity when it comes to promoting physical activity for kids.

    For that matter, we're probably also on the same page regarding kids and healty foods (and what to measure there).

    I think that one of the greatest contributors to childhood overweight (I would use Ellyn Satter's definition of weight in excess for a particular child above his or her "natural" weight) is targeting of kids by corporations. Which doesn't only make kids want to eat foods that aren't good for them (more often than as an occassional treat) but also underminds the healthy parent-child relationship. For the most part, my own 3.5 year old has rarely gone shopping for anything, let alone food.

    If I can gently make a recommendation, it would be to talk more about how marketing to kids impacts their health overall, in terms of relationships, self-perception, as well as the impact it has on making some kids fatter than they would otherwise naturally be.