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 coauthor 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 ages 2 and older. Last month, a survey of children ages 0 to 2 showed the number of babies considered overweight or at risk for becoming so has increased dramatically 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% of babies ages 0 to 5.9 months were overweight in 2001 -- a 73.5% increase from 1980. An additional 11.1% were at risk of becoming overweight. Among children ages 6 to 11.9 months, 9% were overweight in 2001-- a 20% increase -- and 14.4% were at risk for becoming so.
Babies are considered overweight if they have a score linking weight to height that is greater than 95% 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 Assn.'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 from coast to coast.
But there is debate on how useful these charts are, as well as which charts to use.