By analyzing the height of growing infants rather than body-mass index, researchers say they are able to accurately predict obesity later in life.

Susan Ludington from Case Western Reserve University led the research, which analyzed 221 healthy children who had weight, height and medical records from nine check-ups during the first five years of their life.

The researchers found that, by age 5, normal-weight children developed differently from birth than those considered overweight, obese or severely obese.

By assessing statistical plots of height and weight as babies aged, the researchers learned that normal-weight babies with a body-mass index (BMI) in the 17th percentile plateaued at about two months and rarely deviated over the next five years. Overweight or obese babies crossed the 17th percentile almost a year later and continued an upward climb when BMI growth patterns were monitored.

The study's authors claim their work is the first study of early weight changes that only used healthy infants and children: none of the subjects had a hospital or emergency room visit, medical procedure, special medical condition or any medications that might have skewed results.

"We didn't want anything to interfere with regular eating," Ludington said in a news release.

Based on prior research, Ludington and colleagues report that how a mother ate during pregnancy might have contributed to a baby's hormones and its ability to satisfy hunger.

Instead of using BMI scores as a guideline, Harold Haller, director of Case Western Reserve's Center for Statistical Consulting, plotted on a graph a baby's weight divided by height. By graphing the result, a pattern emerged that found both girls and boys known to be obese at 5 began to show significantly higher weight over height than normal weight babies as early as 2-4 months of age.

Ludington said the find is significant because a trend emerges before children generally start eating solid food. She said early life growth patterns may provide important information about a person's future health issues, as well as be a predictor of obesity that may come to change the age at which obesity is diagnosed. Currently, obesity isn't diagnosed until a person is more than 2 years old.

Researchers at Tennessee State University also contributed to the study, which was published in the journal Clinical Pediatrics.