For babies and young children who are above the percentile curves, talk of intervention should focus squarely on the development of healthful habits. “We are not talking about weight loss in younger or even older children. We want kids to grow in a healthy manner, without putting on too much fat,” said Dr. Gillman.
Toward this end, actively monitoring children's weight status is an important component of obesity prevention, although there is a lack of data available on infants in this realm. “We don't yet know the optimal weight gain during infancy for short- and long-term outcomes, so for now [physicians] and parents should aim for growth in weight for length along the percentile curves in the growth charts that doctors use,” he said.
Growth Charts
The use of growth charts has been the subject of some controversy in recent years. In the United States, most physicians rely on the CDC 2000 growth reference in which the development of an individual child is plotted against the rate of growth of the “average” American child, as determined from a limited sample.
The problem with this approach, according to Dr. Cutberto Garza, provost and dean of faculties at Boston College, is that the measure does not provide a scientific assessment of healthy growth based on a large sample of infants and children whose feeding habits and environment are consistent with good health outcomes.
A growth chart should be an assessment tool that shows not only how a child is growing but also whether the child is growing as he or she should, Dr. Garza, who chaired the WHO Multicenter Growth Reference Study from which the new standards were generated, said in an interview.
New growth standards introduced by WHO in April of this year were designed to fit this bill, he said. The goal of the study was to develop standards based on the growth and development of healthy infants and children up to 5 years old from around the world.
In total, the investigators compiled primary growth data for 8,500 children from six ethnically and culturally diverse countries (Brazil, Ghana, India, Norway, Oman, and the United States). The children were selected based on predefined criteria for feeding practices, nutrition, and health care that have been previously associated with good health outcomes.
For the purposes of the study, breast-feeding—including exclusive/predominant breast-feeding for at least the first 4–6 months of life and continued complementary breast-feeding for at least 1 year—was considered the normative behavior for infant feeding.
The study showed that, despite individual differences among the children, the average growth across the board was similar, indicating the important influence of healthy growth conditions in early life, Dr. Garza said.
The resulting standards are representative of physiologic growth and include charts based on longitudinal data for infants from birth to 2 years and charts based on cross-sectional data for children from 2 to 5 years. Separate curves for boys and girls include a variety of growth indicators such as weight for age, length/height for age, and weight for length/height, as well as a body mass index standard for children up to age 5.
Eventually, velocity standards as well as attained head circumference, skin-fold thickness, and mid-arm circumference standards will be incorporated, according to Dr. Garza (
With the WHO curves, more babies and young children in the United States fall into an overweight category, compared with the CDC growth chart, possibly because a smaller percentage of U.S. babies are breast-fed, and breast-fed babies tend to be leaner than formula-fed babies.
This does not diminish the relevance of the growth curves in the United States, according to Dr. Garza. Rather, “it highlights the fact that breast-feeding is an important early risk reduction factor and should be promoted as such.”
It has yet to be determined whether the United States will adopt the new WHO standard or adapt existing standards to include some of the important changes, but the possibility was put on the table in late June at a meeting of the CDC, the National Institutes of Health, and the American Academy of Pediatrics, according to Dr. Frank R. Greer, chairman of the AAP Committee on Nutrition. Any new recommendations would need to be accompanied by guidance for clinicians on how to interpret the changes, he said in an interview.
In terms of clinical application, the role of the new standards is basically unchanged, Dr. Garza stated. “It's a mistake to use anthropometric data for diagnostic purposes. The clinical uses are to assess risk to either excessive or inadequate growth and to assess responses to treatments designed to positively impact growth.”