WASHINGTON — Guard your lunch box. Today the Institute of Medicine (IOM) released a report proposing new guidelines for foods offered in schools. The recommendations reduce all food in competition with the National School Lunch Program into a three-tiered hierarchy: the good, the bad, and the unwelcome.

The immediate problems with this report are bountiful, but it’s the future implications that are most disconcerting. And despite the fact that almost all research on in-school nutrition indicates that bans are ineffective (and counterproductive at times), the IOM report declares war on everything from chewing gum to potato chips.

The narrow standards for “Tier 1 Foods” will effectively squeeze everything but fruit juice, nuts, and a small assortment of produce out of the cafeteria snack bar. And the guidelines don’t stop there. The rules outline where and when permissible foods can be sold, which athletic teams can drink sports drinks, and effectively call for a ban on fundraisers like bake sales.

These restrictions don’t stop at the school cafeteria. The food provided at booster clubs, PTA meetings, parent-teacher nights, and other adult activities held on school grounds will be subject to scrutiny as well.

These decrees may seem surreal, but many schools have already implemented similar measures. Birthday celebrations that include cupcakes have been banned in classrooms across the nation. Many schools forbid parents from bringing their kids fast food.

While the sale of certain foods in schools is commonly blamed for childhood obesity, a new report released yesterday reveals that physical inactivity, not food availability, is the leading cause of childhood obesity. The non-profit Center for Consumer Freedom’s (CCF) report, “Sedentary Kids: Why Food and Drink Bans Don’t Fight Obesity,” warns that attempts to regulate food choice fail to address the need for more activity.

“Science shows that when it comes to obesity, even in childhood, diet is just one part of the equation,” said Senior Research Analyst J. Justin Wilson. “Far more import is the amount of physical activity people engage in. School officials truly committed to addressing the whole problem should shift their focus from the cafeteria to the playground and the school gym.”