fitness · kids and exercise

Twist surprise endings? For movies– fine; for exercise studies, not so fine

I’m not a horror fan at all.  The blood and gore just gross me out, even if they’re comically unrealistic. But the worst part for me (which I know is the best part for others) is the surprise twists, especially at the end.  I get confused, distracted, scared if it’s scary, and really grossed out to the point of nightmares sometimes. And this includes experiences even after the age of 10. So I don’t watch them.

We know to steel ourselves for surprise twists at the end of movies.  But who prepares themself for an out-of-the-blue and contrary-to-the-plot twist in an article on  the connections between physical activity and health in kids? Not me, and probably not you.

 

Square computer-generated sad person, with "This person is not available" message.
Square computer-generated sad person, with “This person is not available” message.

 

So imagine my surprise when, while reading an article reporting results of a study finding a correlation between more time spent being physically active and better metabolic health among adolescents, it switches gears completely at the end, saying this:

Professor Bell explains: “This suggests that it’s never too late to benefit from physical activity, but also that we need to remove barriers that make activity hard to maintain. Keeping it up is key. This includes making weight loss via diet a priority, since higher weight is itself a barrier to moving.”

 

Say what?!
Say what?!
balloon with typographical marks indicating "What?!"
balloon with typographical marks indicating “What?!”

Here is what the study itself said:

A group about 1800 girls and boys born around 1991-92 were studied on three different occasions from 2003 to 2008.  The researchers were looking for connections between levels of physical activity and biological markers of their overall metabolic health (e.g. cholesterol types, triglycerides, etc.– 230 in total).  What they found was this:

  • Better metabolic health was associated with recent moderate-to-vigorous physical activity, regardless of previous activity patterns (this is a bit more complex, but basically correct).
  • Worse metabolic health was associated with more sedentary activity patterns.
  • The correlation between moderate-to-vigorous activity and metabolic health wasn’t weaker for subgroups with higher body fat (which could mean those who have a history of less physical activity, or also those with higher BMI).

They conclude here:

Our results support associations of physical activity with metabolic traits that are small in magnitude and more robust for higher MVPA [moderate to vigorous physical activity] than lower sedentary time. Activity fluctuates over time, but associations of current activity with most metabolic traits do not differ by previous activity. This suggests that the metabolic effects of physical activity, if causal, depend on most recent engagement.

There’s nothing here about losing weight as a causal factor or salient feature in their analysis.  So why did the main author say that in the article? I decided to dig a little deeper, which means going to the original full article.  I’m doing it, so you don’t have to– it’s part of the service we provide at Fit is a Feminist Issue.

 Person in tuxedo, holding a tray with message "full service".
Person in tuxedo, holding a tray with message “full service”.

 

Here’s what’s going on: in their discussion of where their study fits in the literature on metabolic health, physical activity, body weight, and risks for e.g. type 2 diabetes in youth, they say this:

much of the association of higher activity with lower subsequent adiposity is driven by reverse causation in this data… [there appears to be] a lowering effect of total activity on fat mass and blood pressure… The standardised effect size was 6 times larger in the reverse direction, however—from fat mass to inactivity—suggesting that adiposity affects activity levels more than activity levels affect adiposity.

Effect sizes matter a great deal for public health messaging since the existence of an association, or indeed a causal effect, does not alone describe its importance. Future work should compare magnitudes of effect size between common risk factors as the rate of discovery and the need to prioritise limited public health resources both increase.

The researchers say their results (and literature) support the idea that (in adolescents), body weight affects physical activity levels up to 6 times as much as activity level affects body weight.  This part is no surprise, as loads of studies support the view that exercise doesn’t result in much of any weight loss.

Here’s a surprise, though (and this one isn’t scary, so it’s okay to keep reading): saying that body weight influences physical activity (that is, kids with higher body weights tend to be less active) means to the researchers that we need to work on our public health messaging, as this is very important.

YES!  Of course we need to work on this. Movement at every size and shape and ability (and age, too, of course) helps us in just about every way.

But then (now the scary part is coming, be warned), the main researcher, Joshua Bell (not the violinist, I assume) has to go and say that, because higher weights are a barrier to increased physical activity, that kids should “make weight loss via diet a priority.”

A big NO.
A big NO.

 

Why no? Because 1) no one knows how to bring about and maintain weight loss via diet in kids (or anyone else); 2) we do know how to remove barriers to increased physical activity for kids with higher body weights. How do we do this?

  • attack fat shaming and weight stigmatization of kids everywhere we find it;
  • create opportunities for fun, non-competitive, easy-to-do movement for kids, done at their own pace and for reasonable time lengths, with no measuring, and lots of assistance and support;
  • work on ways to incorporate those conditions for movement into the everyday lives of kids and the people around them;
  • never use the word diet again around them (or anyone, for that matter).

This kind of public health messaging and programming is something we can all agree to.  And that’s no surprise.

The End, with scary shadowy castle in background.
The End, with scary shadowy castle in background.

 

 

 

 

 

One thought on “Twist surprise endings? For movies– fine; for exercise studies, not so fine

  1. I dropped PE at the first possible opportunity (after tenth grade), in part because I hated public weigh-ins and body-fat caliper testing (which the boys didn’t have to do), but also because I had no great liking for most of the activities that formed the majority of the curriculum (team sports and the stench of the weight room were serious turn-offs). I was one of the tallest girls in the class, and healthy, if not lean, at a weight that would have been pushing overweight, if not obesity, for many of my smaller classmates. Only one girl out-weighed me, and she was a natural athlete with a much more muscular build and less genetic tendency toward body fat retention. This saved her from a lot of the (petite) teacher’s lectures about the risks of excess weight and (perceived) lack of activity.

    I wasn’t particularly fast or fond of running (elementary school skiing injuries and the resulting damp-weather arthritis made that a painful chore rather than the joy that some classmates found it to be). I was a lot stronger than I looked (growing up doing farm chores will do that for anyone). But I was still singled out for my weight/body fat percentage – “you’re so strong, why aren’t you leaner?”. And this was in the 80s, where lean and sculpted was everything. It had an impact, even when the messaging at home was centred around celebrating what the body could do, not what it looked like. Thirty-plus years on, I still struggle with the mixed messaging, except now it also has sexual and ageist overtones, too.

    To complicate matters, my personality is such that when pushed in a particular direction (even one I want to go), I dig in my heels and refuse to move. I want to become stronger and more active, but as soon as I receive any outside praise for efforts in that direction, my brain says “F*** you, that’s none of your business” and kills my own motivation. Some days it’s a serious Catch-22. But you know what? I’ve actually managed, through this rant, to somehow persuade myself to take my European town bike out for a short cruise around the local forest park. Adieu, and thank you for the opportunity to vent.

    Like

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