Canteen break contributes to obesity?

I think a lot of schools have this practice of getting overweight students to do some physical activity during recess time to help them lose weight. They are not the only ones who does activities though - lots of boys (esp the lower sec students) will play football, basketball, catching, hide and seek, while the girls largely congregate in the canteen to talk, but perhaps only half of them buy something to eat or drink.

Teachers are always doing more of anything than the students, and none of us eat during recess, usually having our meals after 1.30pm after school ends. On some days, I cycle hard to school, run around prepare my lessons, execute 2 hours of PE lessons, and prepare/teach English too before having some food. If there's really no need to eat during recess, does that means that we are actually encouraging overeating (and eating at irregular hours) by giving them a food break at 10-11am?