Body mass index (BMI) during infancy may help to predict if a child will be obese by age four.
In a study focused on the infant BMI-childhood obesity relationship in a cohort with a majority of African-American children, researchers from The Children's Hospital of Philadelphia (CHOP) say that a better understanding of infant growth patterns may lead to more effective early efforts at obesity prevention.
'Given the public health importance of obesity related medical problems, we investigated whether BMI in infants could be used as a tool to identify children at increased risk of future obesity, to develop better prevention strategies,' said study leader Shana E. McCormack, MD, a paediatric endocrinologist at CHOP. 'We also analysed ancestry based differences in growth patterns, and found differences that were apparent at as early as 9 months of age were ultimately related to childhood obesity risk.'
As a measure that includes both weight and height, BMI is an approximation of body fat content. BMI increases after birth, reaching its peak in infancy, usually between 8 and 9 months of age. The current study analysed the electronic health records of 2114 healthy Philadelphia-area infants, as part of a larger study conducted by CHOP's Center for Applied Genomics.
Sixty one per cent of the children in the study cohort were African-American, a population that, according to national estimates, has high rates of obesity and diabetes in adulthood. Investigators hope that more reliable, early identification of all infants at increased risk for obesity will offer a unique opportunity to develop and implement targeted interventions.
The research team identified significantly different growth trajectories between African-American infants and white infants. Peak infant BMI occurred around 12 days earlier in African-American children, and was about 3% higher in magnitude than others in the study, who were primarily of European ancestry. Overall, African-American infants appeared to have more than twice the risk of obesity at age four compared with infants of primarily European ancestry.
However, the study team performed statistical analyses to distinguish the effects of ancestry and infancy BMI, while also accounting for other factors such as birth weight and socioeconomic status. Their conclusion was that infancy BMI played a more important role than ancestry in determining the risk of childhood obesity. In addition, socioeconomic factors, inferred from geographic and insurance data, played a role in infancy BMI. Higher rates of poverty, for instance, were associated with higher and earlier peak BMI.
The team added that the current study provides rich longitudinal data, including drawing on the many measurements that are made routinely during infancy and early childhood at well-child check-ups. It is one of the largest studies to date using longitudinal data in such a diverse population.
In children under age 2, there is currently no consensus definition of obesity, said McCormack, who added: 'In the absence of an accepted, valid definition of obesity in infancy, we struggle both as researchers and clinicians with how to best individualise recommendations for infants to prevent childhood obesity. Our findings suggest that infant BMI pattern could be one additional tool. In addition, infant BMI may be an early metric to use in evaluating the impact of public policy interventions.'
The paper is available online here.