Does Baby’s BMI Really Matter?

Those rolls are adorable, but could they be pointing at future health risks New research shows that a baby’s body mass index (BMI) at 2 months can be a strong indicator of obesity by age 2.

The study, published in the April edition of Pediatrics, certainly isn’t advocating for parents to put baby on a restrictive diet. And there’s currently no accepted definition for excess body weight below age 2, especially since weight gain occurs at all different rates during infancy. The purpose of monitoring a baby’s BMI, according to researchers, is to identify at-risk infants and nip obesity in the bud.

“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,” says lead author Sani Roy, MD, a pediatric endocrinology fellow at The Children’s Hospital of Philadelphia (CHOP).

An earlier study in the Journal of Obesity highlights some of those potential interventions, like breastfeeding, introducing nutritious complementary foods by six months, responding to hunger and satiety cues and making sure baby is getting proper sleep.

Evaluating BMI would mark a shift in practice for pediatricians, who currently measure weight-for-length (WFL). But unlike BMI, WFL doesn’t account for age, an important metric when evaluating excess weight gain.

“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,” says senior author Babette S. Zemel, PhD. In looking at records from 74,000 full-term infants, the team “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,” she says. “We recommend that clinicians consider measuring BMI in early infancy.” In the meantime, if you’re wondering where your baby stands, check out the growth chart percentiles used by the World Health Organization.