Teenagers' weight often stays stable

By Amy Norton

NEW YORK (Reuters Health) - Teenagers' weight seems to remain fairly stable over time, a new study suggests, implying that the optimal time to prevent obesity may be earlier in childhood.

In a study of 1,746 adolescents, researchers found that the percentages who were overweight or at risk of becoming overweight held steady over three years. At the outset, 18 percent and 19 percent were overweight or at risk, respectively.

Three years later, those figures remained nearly the same, according to findings published in the Journal of Pediatrics. What's more, the researchers found, the average body mass index (BMI) score for the group was the same at the beginning and end of the study.

The one exception was that teenagers who were the leanest at the outset tended to have larger-than-expected gains in BMI, particularly girls.

It's not clear whether the BMI gains in the leanest teenagers should be concerning, according to the researchers, from Cincinnati Children's Hospital in Ohio.

These teens still fell into the normal BMI range at the study's end, said Dr. Jessica Woo, an assistant professor of pediatrics who was involved in the study.

What the findings do suggest, she told Reuters Health, is that it may be best to prevent excessive weight gain in early to mid-childhood, rather than adolescence.

On average, the children were 14 years old during the first year of the study. At this point, Woo said, "we already saw a significant proportion of our adolescents at or above the clinical thresholds for overweight."

And contrary to what the researchers expected, very few teens gained excessive weight during the study period, Woo added.

All of this, she said, suggests there is a "critical time" for weight gain, and therefore obesity prevention, earlier in childhood.

SOURCE: Journal of Pediatrics, October 2007.