Girls are most likely to gain weight early in adolescence, between the ages of 9 and 12, a new report finds.

And the health consequences of being overweight can be evident in girls as young as 9, all of which points to the need to tailor prevention efforts to ever younger ages.

"We really need to get to kids before age 9 and 10, and this really puts the pressure on elementary school, preschool and whatever societal institutions we have to really focus on young ages," said study co-author Eva Obarzanek, a research nutritionist at the U.S. National Heart, Lung, and Blood Institute.

The study is published in the January issue of the Journal of Pediatrics.

"This shows that obesity and other risk factors for heart disease track from younger to older. This is a wake-up call for policymakers, for schools, for parents," said Arlene Spark, associate professor of nutrition at Hunter College, in New York City. "The success rate for treatment is practically zero. The only thing that we can really hope for is that we can prevent children from becoming overweight and obese."

Dr. Bonita H. Franklin, a clinical assistant professor of pediatrics at New York University School of Medicine, added: "Heart disease is the major cause of mortality in adults in the U.S. This is implying that these factors which are known to make heart disease more likely in adults are already present in young children, so you would presume that there would be an increased health burden and probably shorter life span for this next generation."

The childhood obesity epidemic in the United States continues to worsen. Between 1976 and 1980, 4 percent to 6 percent of children were overweight. By 1999-2002, that number had climbed to 16 percent.

Being overweight, even as a child, increases the likelihood of having risk factors for cardiovascular disease, including higher blood pressure as well as elevated cholesterol, triglyceride and fasting insulin levels.

For this study, more than 2,300 girls aged 9 and 10 were enrolled and followed for at least a decade. Researchers measured their height, weight, blood pressure and cholesterol every year through age 18, then had the teens report their own measures at ages 21 through 23. Roughly half of the girls were white and half were black.

Longitudinal studies, which follow the same individuals for a period of time, are unusual in science because they are so expensive, but yield very valuable data.

"That it's longitudinal is excellent," Spark said.

Rates of overweight among the participants increased through adolescence, from 7 percent to 10 percent in the white girls and 17 percent to 24 percent in the black girls. Girls were 1.6 times more likely to become overweight when they were aged 9 through 12 than later in adolescence. And girls who were overweight during childhood were 11 to 30 times more likely to be obese as young adults.

Being overweight also made girls more likely to have elevated blood pressure and cholesterol levels compared to girls of normal weight.

"We put a biological value to the definition that we use for overweight for children," Obarzanek said. "We attach a health consequence to that cut-off point. In these days of evidence-based medicine, this really is strong evidence."

There were also racial differences, with black girls 1.5 times more likely to become overweight at any given age than white girls. Between ages 9 and 18, the prevalence of overweight was higher among black girls (rising from 17 percent to 24 percent) compared with white girls (rising from 7 percent to 10 percent).

Prevention efforts need to focus both on younger ages and take into account cultural differences, the authors stated.

"This is concerning, but I wouldn't say that it's hopeless," Franklin said. "Efforts to work with preteens would be very important. The younger, the better."