Obesity Epidemic Spreads to Infants

BOSTON, Aug. 10 -- There are a lot more chubby babies than there used to be. That goes for chubby preschoolers, too.

During a 22-year observational study, the ranks of overweight children grew by almost 60%, with more than a 70% increase for overweight infants, according to a study published online in Obesity.

"Rates of overweight are increasing in very young children, even infants, from primarily middle-class families," wrote Matthew Gillman, M.D., of Harvard Medical School, and colleagues.

This increase may be a particular problem since early childhood sets the stage for later weight problems and their related sequelae, the investigators said. "Our observation of a trend of increasing weight among young infants may portend continued increase in childhood and adult obesity," they wrote.

The study found an overall unadjusted prevalence of overweight rising from 6.3% in 1980 to 10.0% in 2001 for children under the age of six. Currently, as many as 65% of adults in America are overweight and 16% of young people ages six to 19 years old are considered overweight.

Dr. Gillman and colleagues looked at height, weight and demographic data from more than 120,000 children under the age of six seen by a Massachusetts health maintenance organization from 1980 to 2001. The researchers randomly selected one visit per year for each child to eliminate double counting.

They used the CDC's growth charts and defined at-risk-for-overweight and overweight, respectively, as a weight-for-height index for age and gender between the national 85th and 95th percentiles and greater than the 95th percentile.

The researchers discovered a nearly linear increase in the prevalence of both conditions over time.

The unadjusted prevalence of overweight rose from 3.4% to 5.9% for children younger than six months, from 7.5% to 9.0% for those six to 12 months old, from 10.3% to 12.3% for those 12 to 24 months, from 5.4% to 10.6% for children 24 to 36 months, and from 5.9% to 10.3% for those 36 to 72 months. Adjusting for ethnicity yielded similar results.

At-risk-for-overweight showed a similar trend with the greatest increase in prevalence for the youngest and oldest children in the study. Overall the prevalence was 11.1% in 1980 to 1981 and rose to 14.4% in 2000 to 2001.

The CDC's growth charts for children under the age of two years were derived using a smaller sample of children than growth charts for older children, so the authors recommended caution in making comparisons across age groups.

Previous studies, including the National Health and Nutrition Examination Survey (NHANES) and the Pediatric Nutrition Surveillance System (PedNSS), have confirmed the same trend in U.S. pediatric populations. However, this is the first study to define the prevalence of overweight in middle-class children younger than two years.

As seen in the previous studies, children insured by Medicaid had a slightly accelerated increase compared with those who were not (an absolute increase of 1.3% in prevalence over the 22-year period compared to 0.9% increase). Similarly, girls and Hispanic children had greater relative rises in overweight prevalence compared with boys and Caucasian children respectively.

Mean body size also rose as measured by z score. Z score compares a mean in a given year against a standard population mean and a higher z score implies an increase in the body measure of interest. The mean weight-for-age z score increased from -- 0.05 to 0.27 while the height-for age z score grew from 0.05 to 0.23 and the weight-for-height z score climbed from 0.01 to 0.30.

Physicians need to take an active role in improving treatment methods and prevention efforts for childhood obesity, the authors concluded. They suggested actively monitoring the weight status of young patients.