I’ve been following the hand wringing about childhood obesity for at least ten years. And in spite of all the alarm bells, finger-pointing and declarations of doom I have yet to see evidence that very much has changed.
There are lots of reasons for that, the chief one being that societal trends are hard to change. However, one problem I see is that those who are trying to influence the public through advice and policy, are putting too much emphasis on physical activity and exercise as the way to get kids to slim down.
We are in love with the idea that exercise burns off the weight. And while most reputable experts will say that losing weight or preventing weight gain is about “forks” as well as “feet”, the persistent message is that physical activity is more important. For example, an old ParticipACTION ad that can still be found online depicts the chubby letter a in the word “fat” morphing into the slim letter “i” in the word “fit”, all through exercise. No mention of diet changes. Recently the Globe and Mail ran a series of profiles of successful weight losers. And while each mentioned diet changes at some point, the photo always showed them exercising and exercise got by far more ink in the profile.
This is misleading. Exercise is really good for you, in lots of different ways, but research shows that if you want people to lose weight or gain less weight, you’ve got to change the way they eat. Granted, it is possible to lose weight through exercise alone (particularly under highly controlled conditions, i.e. In a lab study), but in real life studies, where people increase exercise on their own and don’t change their diet, weight losses are pretty unimpressive, in some cases minimal. I wrote in detail about this research recently in More magazine.
But back to fighting “childhood obesity.”
One big anti-childhood obesity initiative in Ontario, where I live, is mandatory daily physical activity in schools. When this was introduced in 2005 the Ministry of Education rightly noted that physical activity was good for children on various levels, but what got the most attention in the media and in statements by politicians and health promoters was that the policy would combat childhood obesity.
Not likely. A meta-analysis of 18 studies on school activity programs, published in the Canadian Medical Association Journal, found that school physical activity programs did not improve children’s body mass index. A study in the U.K. found that kids who went to schools where high levels of physical activity were built into programming were less active at home, and no more active overall, than kids who did much less physical activity at school. The authors suggested this was evidence that some sort of internal mechanism, which they call an “activitystat,” regulates physical activity in children. Thus, if kids get a lot of physical activity in one setting, their body seems to cue them to be less active in other settings.
Another British study monitored children’s physical activity levels with devices called actigraph accelerators and tracked their BMI and body fat levels (skinfold thickness) for four years. There was no relationship between physical activity levels and getting fatter (or not). Mind you, they did find that more active kids had better metabolic status (lower insulin resistance and blood pressure, better cholesterol/HDL ratio). (I thank Dr. Yoni Freedhoff for showing me this research. Dr. Freedhoff, an exercise advocate and avid runner BTW, nonetheless seems to be the chief champion of diet changes as the most important part of weight loss. Check out his excellent blog weightymatters.ca)
So the point here is not that encouraging physical activity in kids or mandating daily physical activity in schools is bad policy. It’s very good policy. Overweight children who exercise are healthier than those who don’t. And I’m excited about research that shows that physical activity can improve some children’s behavior and learning. Just don’t try to tell yourself that it is the solution to overweight children (or adults).
But what about screen time? It doesn’t take a scientist to figure out that more kids are spending more time sitting in front of TV, computer and video game screens these days. Many commentators point to the resulting reduced physical activity as a contributor to increasing childhood obesity. Maybe, but some research is suggesting that the main contribution of screen time to overweight children is that it tends to increase junk food consumption.
So, by all means, let’s get kids moving, as Michelle Obama and others say. But if we really want to make a dent in problem of overweight children (and grownups) we have to change what they are eating.
That will require a big shift in the way a lot of people think and behave about the food they eat (I want to acknowledge that many, many people are already eating well, sensibly and moderately). That’s a huge topic, which will be difficult because it involved taking on the food industry. But at the micro level, the nut of it seems to be eating more real food (more fruits and vegetables, more home-made meals with fresh ingredients, more meals at home in general) and less packaged food, less junk food and, generally, less food away from home. That’s a hard change to bring about, especially given how busy many families’ lives are, and the way the food industry is there to help us with ever-expanding array of handy prepared foods and fast food joints with foods that kids love. (Yes, my kids ate their fair share of this stuff too). Changing the way we, and our kids, eat will take considerable effort, and it’s harder come up with sound and (pun intended) palatable, policies about that.
But a good first step would be less public messaging that implies that exercise is the key to weight loss. No need to stop talking about the importance of exercise for children. It’s very important. Just don’t count on it to reduce the number of overweight kids.