Some of our best memories of elementary school, beside recess, of course, are the class parties. First there’s Halloween, hallowed with cartloads of candy. Then come the winter holidays, packed with pies, cookies and baked goods. You can’t have Valentine’s Day without chocolate, and then there are birthdays throughout the year to celebrate with cake and ice cream.

But the cold reality of such revelry is that those extra calories can take a toll on growing boys and girls. Add them all up and over the course of a year, the pounds could pile on.

A new study published in the Journal of Nutrition, Education, and Behavior found that kids can eat as many as one-third of all their daily calories at a typical half-hour birthday party. No one wants to be the sweets police, but too much sugar is cause for concern considering one in five children in the United States is overweight or obese.

For the study, researchers observed four classroom birthday parties for preschoolers and kindergartners and took note of what food and drinks were served and how much kids ate. Typical birthday fare included chocolate cake, ice cream, punch and chips.

Each kid ate an astounding average of three hundred forty-four to four hundred fifty-five calories. But when fresh fruit was served alongside the caloric confections, the damage dropped to two hundred fifty-nine to four hundred five calories.

The results give reason to slim down school parties. Serve healthy snacks like low-fat popcorn and graham crackers. If cake is required, downsize portions and limit kids to one serving. Even better, make parties more about fun and less about food. Provide plenty of active games or designate the birthday boy or girl as the teacher’s special assistant to deliver items to the front office. Keeping the classroom low in calories can be a smart step toward a healthier lifestyle.