"There has been widespread recognition in the past few years of how important it is to prevent obesity in children. These findings underscore that even children who are in the high normal weight range may have adverse outcomes later in life, and our challenge may be even greater than we thought.

The study was conducted over nearly a decade at the Harvard Medical School (HMS) and Harvard Pilgrim Health Care Department of Ambulatory Care and Prevention and Children's Hospital Boston.

"We have known that kids who are overweight or obese have a higher risk for being overweight or obese as adults. But in this paper, we show that even children in the high normal weight range have an elevated risk of becoming overweight or obese as adults," says lead author Alison Field, assistant professor of pediatrics at HMS and Children's Hospital Boston.

BMI as Adult Obesity Predictor

Children with a body mass index, or BMI, between the national 85th and 95th percentiles for age and gender are classified as "at risk" for being overweight, and those with a BMI greater than the 95th percentile are classified as "overweight" according to the Centers for Disease Control and Prevention's national reference data.

The authors considered a body mass index (BMI) between the 50th and 84th percentile to be in the "high normal" weight range.

The study comprised 314 children, mostly Caucasian, from East Boston, Massachusetts, who were 8 to 15 years old when their weight, height, and blood pressure were first recorded. They were again evaluated 8 to 12 years later.

Results showed that nearly half of the male subjects (48.3 percent) and nearly a quarter of the female subjects (23.5 percent) became overweight or obese between their first childhood visit and the young adult follow-up.

Compared with children with a BMI less than the 50th percentile, girls and boys between the 50th and 74th percentile were five times more likely to become overweight. Boys and girls with a BMI between the 75th and 84th percentile were up to 20 times more likely to become overweight as young adults.

Risk of Hypertension

The results also showed that among the boys, elevated BMI in childhood predicted risk of high blood pressure (hypertension) in young adulthood. Compared with boys who had a childhood BMI below the 75th percentile, boys between the 75th and 85th percentile of BMI as children were four times more likely to become hypertensive. Boys at or above the 85th percentile were five times more likely to become hypertensive.

"There has been widespread recognition in the past few years of how important it is to prevent obesity in children. These findings underscore that even children who are in the high normal weight range may have adverse outcomes later in life, and our challenge may be even greater than we thought," says Matthew Gillman, senior author on the paper and associate professor of ambulatory care and prevention at HMS.

"We must focus not only on the most obese kids but also on those who are just a bit overweight," he urges.

Click here to access the Centers for Disease Control and Prevention's BMI charts for children and teens.