Last Friday a group of French doctors announced that childhood obesity in their country is catching up to that of American kids. There’s no disputing that obesity is on the rise throughout the world, but the question remains: why is this happening? Drawing on science (and common sense), we answered this question in an op-ed published in the Philadelphia Inquirer:

It might not be technically true that grandpa got to school by walking three miles in the snow, uphill both ways. But a generation ago, 80 percent of children walked or biked to school, at least occasionally. Now, more than 80 percent never do.

Today’s kids are six times more likely to play a video game than ride a bike in a given day. Meanwhile, just a quarter of high-schoolers are enrolled in PE class at any one time. No wonder there are increasing numbers of pudgy kids.

Some activists and academics have convinced themselves that taxes on tasty foods, mandatory portion control laws, or lawsuits against food makers will fight obesity. Not so fast, we say:

Even if you aren’t worried about the implications for personal responsibility, it’s easy to see that these proposals won’t take a real bite out of our waistlines. You can eliminate super-sizing and subsidize broccoli all day long, but if I can hit the all-you-can-eat buffet and then buy chocolate syrup for less than a dollar a pound on the way home, it won’t make a lick of difference.

Times have changed. You can go a month without ever breaking a sweat. Buying tasty food is easy and inexpensive. Those in the growing ranks of former smokers tend to gain weight (CDC researchers estimate that about a quarter of our weight gain can be traced to smoking cessation).

Lest it be forgotten, these changes are, for the most part, good things. Hunting and gathering may have kept us slender, but few would wish to go back.

Short of a magical pill, foolishly encouraging everyone to take up smoking, or abandoning the conveniences of modern life, top-down solutions to obesity just aren’t going to work. We can’t legislate our way out of this problem.

Weight gain can best be tackled person by person, family by family. Take the stairs. Break out the push lawnmower. Choose diet soda. In short, take responsibility. It’s not just a good way to go. It’s the only way.