Baby fat, that term conjuring up images of chunky thighs and thickly padded cheeks, is beginning to carry a new connotation. At a time of so much focus on obesity, the word is that even cute, blubbery babies can be too fat for their own good.
That's the carefully crafted message emerging from several health groups, including the World Health Organization, the Centers for Disease Control and Prevention and the American Academy of Pediatrics.
No one suggests that children younger than 2 should be placed on a diet, but health experts are becoming more convinced that future weight problems can take root in the earliest days of life and that baby weight should be monitored in a more rigorous and thoughtful manner.
In particular, health experts are debating the growth charts used to track weight and height in children, with some organizations such as the WHO advocating new charts that may be more likely to spot excessive growth in babies, and the federal government discussing whether to update its growth charts and add an "obese" category to describe the heaviest children.
"Children don't become obese overnight. It's a process," says Dr. Cutberto Garza, provost at Boston College and co-author of a 2004 WHO study on child growth. "An incredible proportion of our children are getting to kindergarten overweight, and many of us think the earlier we're able to identify a child at risk, and do it in a way that doesn't stigmatize, the better."
There is little doubt that American babies are getting bigger. Several studies have already charted increases in the rates of overweight children 2 and older. Last month, a survey of children from birth to 2 years old showed the number of babies considered overweight or at risk for becoming so has increased drastically since 1980.
The study, published in the journal Obesity, examined records of more than 120,000 children at an HMO in Massachusetts between 1980 and 2001. It found that 5.9 percent of babies from birth to 5.9 months were overweight in 2001 - a 73.5 percent increase from 1980. An additional 11.1 percent were at risk of becoming overweight. Among children 6 months to 11.9 months, 9 percent were overweight in 2001- a 20 percent increase - and 14.4 percent were at risk for becoming so.
Babies are considered overweight if they have a score linking weight to height that is greater than 95 percent of all babies. Babies classified as at risk for becoming overweight fall between the 85th to 95th percentiles.
Yet predicting what will happen to these babies in the future is difficult. As all parents know, some chubby babies and toddlers shed their extra padding and become normal-weight children and teens. Others do not.
The earliest days of life may be especially important in setting a child up for svelteness or plumpness, scientists are finding. Early feeding patterns may program a child's metabolism or other aspects of body physiology to increase the chance of becoming overweight.
For example, a study published last year in the British Medical Journal found that big babies and babies who grow quickly in the first two years of life had a ninefold greater risk of obesity in childhood, adolescence and adulthood.
"It appears as though these early weeks to months may be a critical period," says Dr. Matthew Gillman, an associate professor of ambulatory care and prevention at Harvard Medical School and lead author of the recent U.S. survey on infant weight. "It may be that weight gain in this time of life is somehow more harmful."
Animal studies are yielding some clues as to how this might happen. A study presented in June at the American Diabetes Association's annual meeting found that chronic overfeeding in infant rats increased levels of a hormone known as leptin during infancy. Leptin is involved in the regulation of appetite, and its levels in the body are thought to be an important contributor in the development of obesity.
Various recent studies also suggest that a woman's weight before pregnancy, her nutrition and weight gain during pregnancy, and the early weeks of infant feeding may exert long-term influence on child growth.
"In adults, obesity is better understood. You eat too much, and you slow down, you gain weight and become obese," says Kevin L. Grove, a developmental neurobiologist at Oregon National Primate Research Center and Oregon Health & Science University, and author of the leptin study. "But that doesn't explain as much what happens to children. I really feel there might be a much earlier cause or underlying risk."
Progress by the charts
As these data trickle in, doctors are paying more attention to the infant growth charts that are used in pediatricians' offices coast to coast.
But there is debate on how useful these charts are, as well as which charts to use.
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 breast-fed 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, Garza says. "We should not define how children grow, but how children should grow," he says.
Some U.S. doctors wonder whether the WHO charts are relevant. They note that the charts are based on breast-fed babies, who tend to be leaner. Fewer than 40 percent of U.S. babies are exclusively breast-fed 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 breast-fed babies tend to have a lower risk of obesity later in life. But scientists don't know whether that is because of the nutritional content of breast milk or because mothers who breast-feed tend to be more educated, wealthy and less likely to be overweight. And breast-feeding alone, experts say, is unlikely to save a child from packing on pounds.
"I don't think breast-feeding 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," Garza says. 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 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 percent 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."
Shari Roan writes for the Los Angeles Times.