Earlier this year, the WHO released new child growth charts that differ significantly from the CDC charts used by most U.S. doctors. They are based on a WHO study tracking 8,000 children in six countries from birth to age 5. All the children were breastfed for the first year of life and came from healthy homes. The study found that, regardless of ethnicity, all of the children grew very similarly up to age 5.
The new WHO charts are based on this "optimal growth" curve. The CDC charts, in contrast, show how an individual child compares with the average American child -- regardless of whether this "average" rate of growth is healthy or not.
The WHO charts are designed to be more scientific, says Garza. "We should not define how children grow, but how children \o7should\f7 grow," he says.
Some U.S. doctors wonder if the WHO charts are relevant. They note that the charts are based on breastfed babies, who tend to be leaner. Fewer than 40% of U.S. babies are exclusively breastfed for six months.
Perhaps because of this, the WHO curve differs significantly from the CDC charts and categorizes more American babies as overweight. For example, the average 1-year-old female baby on the CDC chart weighs just less than 21 pounds. The optimal 1-year-old girl on the WHO chart weighs 19.8 pounds.
That difference may be significant. Studies show breastfed babies tend to have a lower risk of obesity later in life. But scientists don't know if that is due to the nutritional content of breast milk or because mothers who breastfeed tend to be more educated, wealthy and less likely to be overweight. And breastfeeding alone, experts say, is unlikely to save a child from packing on pounds.
"I don't think breastfeeding is the be-all and end-all," says Dr. Joseph F. Hagan, a clinical professor of pediatrics at the University of Vermont School of Medicine. "It's very easy for television watching and fast food to undo all the benefits of breastfeeding."
This summer, the CDC, the American Academy of Pediatrics and other health organizations began a series of meetings to discuss the value of the WHO charts and whether to make changes to the CDC charts.
If confusion over charts weren't enough, no one knows quite what to do about babies with high body mass indexes. The new WHO growth charts are not a call to "put kids on diets or take draconian measures," says Garza. And it's traditionally been difficult for doctors to address fears that a baby is gaining too much weight, says Dr. Hillary L. Burdette, an assistant professor of pediatrics at Children's Hospital of Philadelphia.
"Feeding is your way of nurturing your infant," she says. "It's primarily what you do in the first year of life. It's a hard place to tread."
But parents themselves are keenly aware of the nation's obesity problem, she says. She recently conducted a study that found mothers have an accurate idea of when their babies may become overweight. The study, published in the Archives of Pediatrics and Adolescent Medicine, found that infants whose mothers had the highest level of concern had the greatest fat mass at age 5.
Experts say that pediatricians and parents need to discuss infant and baby feeding practices during well-baby checkups. Babies should not be put on diets, but some subtle changes can be recommended, such as switching to 1% milk instead of whole milk in babies 1 year or older and introducing only healthful solid foods.
If parents or other siblings are overweight, extra caution should be taken with the baby's growth, says Dr. Francine Kaufman, director of the center for diabetes and endocrinology at Childrens Hospital Los Angeles. If a family eats a lot of fast food, for example, the baby may be offered a French fry or sip of soda from a sibling or parent's lunch.
"The baby is going to like it. From then on, when the baby sees it, the baby gets it," she says.
The baby years, however, may be the easiest time to divert a child on the road to obesity.
"At my age, if I'm overweight, I have no choice but to lose it," Hagan notes. "In a child, they don't need to lose it. They need to stop growing so fast."
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The kids aren't all right
A new study has found evidence that the nation's rise in obesity rates is creeping into the youngest age groups.
Percentage of overweight babies
(Babies with a weight-for-height index greater than the 95th percentile.)
Source: Obesity, July 2006