"The importantest thing I learned was to stay active and stuff," said Meagan Cancilla, 9, from Sansome School in Canada. "That's so I don't become lazy and sick." Like most 4th graders she spent her recess bouncing between a soccer game, tossing a Frisbee and playing tag. She said she's usually quite active, but realizes now she has to stay that way.

She's part of a study by Manitoba Institute of Child Healt…