All it takes is a trip to the schoolyard to see that children are fatter than they used to be. A 2002 survey found 31 percent of the nation's kids are now above the 85th percentile of body mass index (BMI) for age and sex, which is considered overweight. Various factors—fast-food diets, cuts to physical-education programs, the rise of video games, the decline of the family dinner hour—have been blamed, and the search is on to identify factors that are present when kids are infants and toddlers and will predict their later risk of becoming overweight. Researchers from Stanford University School of Medicine set out to identify the factors that put kids at highest risk.

What the researchers wanted to know: What factors present during infancy or early childhood best predict whether a child will be overweight at age 91/2?

What they did: Researchers tracked 150 kids from birth, recording factors including infant feeding behaviors, what mothers considered an ideal infant body type, caloric intake, maternal return to work, parental eating behaviors, and sleep habits. They checked the children's weight at age 91/2, then used statistical tools to figure out which factors best predicted overweight kids.

What they found: The study identified five risk factors that put kids at risk of becoming overweight. The strongest predictor? Obese parents. "A child with an overweight/obese parent had a 48.1 percent chance of becoming overweight or obese, whereas a child with normal-weight parents had a 13.3 percent chance of becoming overweight or obese," the authors wrote. Kids with a sensitive disposition were also more likely to be overweight. Other risk factors: strong preference for a thin child (those parents may freak out when their babies gain weight rapidly and try to control their eating habits, to no avail) and a smaller amount of daily sleep for the child.

What it means to you: If you're overweight, you may be putting more than your own health at risk!

Caveats: The sample size was fairly small, and the group studied was more educated and less ethnically diverse than the overall population, so findings may not be extrapolated to everyone. Also, some of the factors, like childhood personality type, were based on parental descriptions instead of an outside evaluation.

Find out more: For information on obesity trends and a calculator to figure your own BMI, go to http://www.cdc.gov/

Read the article: Agras, W.S. et al. "Risk Factors for Childhood Overweight: A Prospective Study From Birth to 9.5 Years." The Journal of Pediatrics. July 2004, Vol. 145, No. 1, pp. 20–25.

Abstract online: http://www2.us.elsevierhealth.com