Childhood obesity is a national epidemic—and fast food ads aimed at kids arent helping, the study sayd.

Banning fast-food commercials on kids’ TV shows would reduce childhood obesity by 18 percent says a study published this month in the University of Chicago’s Journal of Law & Economics. According to the study, 23 percent of the food-related ads kids see are for fast food.

Childhood obesity is now the most common chronic disease among children, affecting more than 30 percent of kids, according to the Obesity Action Coalition. And the rate is growing quickly; it has more than tripled since 1980.

But as The New York Times reports:

“There is not a lot of evidence that overweight kids are more likely to watch TV than other kids,” said Michael Grossman, professor of economics at the City University of New York. “We’re arguing the causality is how many messages are aired — seeing more of these messages is leading people to put on weight.”

The Times also points out that since the data for these studies was gathered in the 1990s, Burger King and McDonald’s have both agreed to only advertise healthier products — such as Happy Meals that include apples and milk — to children. Of course, what that story leaves out is that the apples and milk are part of a meal that includes deep-fried chicken nuggets.

There is little hope that the government would ban fast-food advertising to children, even in an Obama administration and with Henry Waxman in charge of the House Energy and Commerce Committee.

Pushback from the fast-food industry, dutifully reported by Fox News, is that the study is based on old information and that parents have control over what their kids eat, not kids themselves.

But other research has clearly shown that commercials influence kids’ food preferences. And all parents know that when it comes to food fights, kids are formidable opponents.