Calculating the body mass index (BMI) of a two-month old baby is better able to predict obesity at age two than using weight-for-length (WFL) charts, the current standard of measurement, according to a new study published online in the journal Pediatrics.
WFL is currently the standard of measurement recommended by the American Academy of Pediatrics, and it is also the predominant standard used worldwide. BMI, on the other hand, is widely used in children over age two years to identify those at risk for health complications of excess weight or future obesity.
While BMI charts are available from birth to age two, they are generally not used in clinical care. Unlike BMI charts, WFL charts do not have an age component; therefore, children with similar WFL may differ greatly in age. Furthermore, since gains in weight and length occur at different rates during infancy, it is important to account for both age and length when evaluating excess weight gain.
“An important factor in preventing obesity in adults is identifying at-risk individuals as early as possible, when interventions may have the greatest effect — even during infancy,” said lead author Sani Roy, M.D., a pediatric endocrinology fellow at The Children’s Hospital of Philadelphia (CHOP). “However, there is no currently accepted definition for excess body weight below age two.”
For the study, the researchers looked at the medical records of nearly 74,000 full-term infants seen during their first two years at well-child visits in the CHOP pediatric network from 2006 to 2011.
The researchers found it very significant that 31 percent of two-month-old babies with BMI at or above the 85th percentile were obese at age two, compared to 23 percent of two-month-olds at the 85th percentile by WFL. At the 97.7th percentile for BMI at age two months, 47 percent of babies were obese at age two years compared to 29 percent by WFL.
“To our knowledge, this was the first study to compare BMI to WFL in predicting future obesity risk in a large, diverse cohort of full-term infants,” said senior author Babette S. Zemel, Ph.D., the director of CHOP’s Nutrition and Growth Laboratory.
“We found that while BMI and WFL agreed after age six months, high BMI at age two months was a better predictor of obesity at two years of age than WFL. We recommend that clinicians consider measuring BMI in early infancy.”