// posted March 21, 2007 by Lou Schuler

Kids, according to this, don't need a lot of exercise to fight off obesity:

Just 15 minutes a day of kicking around a ball or swimming might be enough to keep children from becoming obese, British and U.S. researchers said on Monday.


A study of 5,500 children who agreed to wear a motion sensor device showed that those who exercised more were less likely to be obese -- and that short bursts of intense activity seemed to be the most helpful.


Children who did 15 minutes a day of moderate exercise -- equivalent to a brisk walk -- were 50 percent less likely than inactive children to be obese, the researchers reported.

You can find more detail on the study here.

For some reason, I'm skeptical. Given what we know about how genetics affect both physical activity and weight control -- you could safely say that about 30 to 40 percent of each is genetically determined, based on current thinking -- what evidence do we have that the active kids aren't the ones who're programmed to be active? Or that the obese, inactive kids aren't genetically predestined to be sedentary and to struggle with weight control?

If we took all the heavy, inactive kids and forced them to play soccer for 15 minutes a day, would they be any less heavy? And if we took the thin, active kids and forced them to be sedentary, would they actually gain any weight?

In my admittedly limited experience, certain kids seem to find ways to be inactive even when they're playing a sport. I first saw this when I enrolled my son in a karate class when he was 6 or 7.

The heavy kids in the class would do exactly what the instructor told them to do, and find the least strenuous way to do it. The skinny kids were the opposite.

When the instructor told the kids to go across the room and line up by a wall, the skinny kids would sprint to the wall. One or two would bounce off, fall to the floor, flop around until they got the other kids to laugh, and then jump back up and run to wherever they were supposed to be -- unless they thought they could milk the same stunt for another set of laughs, in which case they'd repeat it until someone told them to stop.

Meanwhile, the heavy kids would walk to the wall and stand there, taking only as many steps as necessary. During kicking and punching drills, they'd do the absolute minimum.

I know I've told that story before, and I apologize for repeating it. I just think it illustrates as well as anything the problem with generic exercise prescriptions. You can put every kid in the school out on the soccer field, but some aren't going to move much, while others won't stop moving until you force them to.

Understand, I'm not making fun of the heavy kids, or assigning some kind of virtue to the hyperactive ones. And I'm not saying that all heavy kids are inactive or unathletic, any more than I'm suggesting that all the skinny ones stay thin because of their dedication to sports and love of physical activity. I'm just pointing out that there's no single prescription for helping the most at-risk kids manage their weight and safeguard their health.

That's why I cringe when I see passages like this:

Obesity is on the rise in many countries, including the United States, where 60 percent of the population is overweight or obese, Britain and elsewhere in Europe.


It is clearly a matter of people eating more calories than they burn off, but experts cannot agree whether diet or exercise is more important -- and which kind of exercise might be best.

Experts will never agree on whether diet or exercise is best because the answer will change according to the circumstances. If you're talking about a kid who's unlikely to ramp up his physical-activity level, then you have to tackle his weight on the nutrition side.

And no one will ever determine "which kind of exercise might be best" because any nimrod can figure out that the best exercise for you is the one you'll continue to do because you enjoy doing it.

I don't know why that's so difficult to understand.

(Thanks to Rannoch Donald for the link.)

Tags: exercise