A new study shows much of a child's "weight fate" is determined by the age of 5.
The study in this week's New England Journal of Medicine also finds nearly half of kids who were obese by the eighth grade were already overweight when they started kindergarten.
The study followed a nationwide sample of more than 7,700 children through grade school.
Overweight 5 year olds were four times as likely as normal-weight children to become obese.
"A lot of the risk of obesity seems to be set, to some extent, really early in life," Solveig Cunningham, a scientist at Emory University, said.
The Centers for Disease Control says some weight gain is normal. In order to keep kids healthy it is important to balance a child's calorie intake and exercise.