Physical activity can also help prevent obesity even when there is a tendency to gain weight due to genetics, Abramson said. Research has shown that 4- to 7-year-old children of active parents were six times as likely to be active. Exercise in school lowers the risk for obesity, whereas time spent watching TV or on the computer playing video games increases the risk.

Research has shown that most babies and toddlers start out liking their bodies, said Abramson. But this doesn't last for girls. By the time girls reach pre-adolescence, many start to suffer from warped body images. "Thirty percent of 9-year-old, 55 percent of 10-year-old and 65 percent of 11-year-old girls think they're fat," he said. "Entering puberty isn't as bad for boys. They're more satisfied with their bodies than before they entered puberty."

Parents can help their children have a healthy body image, he said. They need to understand how they feel about their child's physique and see how that is influencing their behavior. With young children, they should let them choose the clothes they want to wear. With pre-adolescents, parents should talk about the body changes that happen during puberty. And finally, they should encourage their children to have friendships with other children who are less concerned with appearance.