In Fighting Obesity, Is Exercise Really the Answer?

August 17, 2009

By Mark Bishop, Deputy Director

Exercise

At the most simplistic level, obesity is about an imbalance between calories you eat and calories you use. Change the balance and you will gain (or lose) weight. Simple enough.

So in the world of school wellness and obesity policy, there are two main groups: groups that focus on greater access to physical activity, and those that focus on improving the healthfulness of food. Neither are wrong, but neither represents the whole picture. And a recent study just confirmed this.

In short, researchers looked at a couple hundred people (in this case, women who were overweight and previously sedentary) who all increased their levels of exercise and were asked not to change their eating habits. What you'd expect is that those who exercised the most would lose the most weight. What actually happened was surprising:

On average, the women in all the groups, even the control group, lost weight, but the women who exercised — sweating it out with a trainer several days a week for six months — did not lose significantly more weight than the control subjects did. (The control-group women may have lost weight because they were filling out those regular health forms, which may have prompted them to consume fewer doughnuts.) Some of the women in each of the four groups actually gained weight, some more than 10 pounds each.

So exercising more doesn't lead to losing weight? Is this crazy?

Well, the thought here is that when we exercise more, our brains allow us to justify additional calories: an extra muffin, an extra slice of pizza, maybe an extra helping of dessert that evening? I know this happens to me every time I go out on a long run — I let myself splurge a bit. Maybe a bit too much.

So what does this have to do with school food policy?

Well, as I mentioned, there are groups that say addressing childhood obesity needs to focus on a single element (activity, food, access), but if this study is accurate, there will never be a single answer. Addressing childhood obesity requires a comprehensive effort — greater access to healthy food, more nutrition education and increased access to physical activity.

And in a small way, this study also hints at the need to shift the way we think about rewards. We tend to think of good food as a good reward for something virtuous, even exercise — an attitude that is reinforced every day in schools when children receive candy or snacks as a reward in their classrooms. (HSC's Quick & Easy Guide to School Wellness includes ideas for classroom rewards that don't focus on unhealthy foods.) Shifting our attitudes about food as a reward is one of those small, show changes that may ultimately be important in efforts to overcome the childhood obesity epidemic.

By the way, I'm training for the Chicago marathon this year, and I just did 17 miles last weekend. But I sure did splurge that evening.