"These findings underscore the need to maintain a healthy weight beginning in early childhood," Dr. Duane Alexander, Director of the National Institute of Child Health and Human Development said in a statement. The NICHD funded the study, which appears in the journal Pediatrics this month.

The study authors advise that being overweight at any time during early childhood should prompt interventions by pediatricians in counseling parents about healthy eating and activity patterns for their child, since obesity in the teen years is highly predictive of obesity in adulthood.

Dr. Philip R. Nader, at the NICHD in Rockville, Maryland, and colleagues tracked the height and weight of roughly 1400 healthy subjects starting in infancy through about 12 years of age. At the end of the study, 1042 children still remained in the sample, of whom 555 had been weighed and measured at all seven points in time.

Results showed that children who were ever overweight in the preschool years were five times more likely to be overweight at age 12 than the rest of the cohort. They defined overweight as having a body mass index (BMI) greater than the 85th percentile for age.

During elementary school years, children who were overweight at 7, 9, and 11 years of age had a 374-fold increased risk of being heavy at age 12 than those who remained below the 85th percentile.

Moreover, 60 percent of children who were ever overweight during preschool years and 80 percent of those ever overweight during elementary school age were overweight at the end of the study.

"These results suggest that any time a child reaches the 85th percentile for BMI may be an appropriate time for intervention," the researchers advise.

Even being in the top 50th percentile by age 3 puts children at higher risk, with 40 percent being overweight at age 12, they note. As would be expected, none of the children who were below the 50th percentile for BMI during elementary school years were overweight at age 12.

Dr. Nader's team urges pediatricians to counsel parents of at-risk children about addressing eating and activity patterns "rather than delaying in hopes that overweight and the patterns that support it will resolve themselves in due course."