American babies carry more "baby fat" now than ever before, a new study finds. Researchers say infants are 59% more likely to be overweight today than they were two decades ago.

"The obesity epidemic in our country has spared no age group, even our very youngest children," said lead researcher Dr. Matthew Gillman, an associate professor of ambulatory care and prevention at Harvard Medical School "Overweight rates are going up in young children, and ours is the first study to show that they are going up in infants, in addition to toddlers and preschoolers," he said.

The Study

In the study of 120,680 children under age six, Gillman's team found that children, especially infants, are now more likely to be overweight. Looking at records collected from pediatricians working with a Massachusetts HMO for the years 1980 to 2001, they found that the prevalence of overweight children climbed from 6.3% to 10% during those 22 years. In addition, the proportion of children at risk of becoming overweight grew from 11.1% to 14.4% overall.

Compared with 20 years ago, infants had a 59% increased risk of being overweight, and the number of overweight infants increased by 74%, the researchers found.

Risk Factors

The data suggest that obesity prevention may need to start even before babies are born, Gillman said. There are a number of factors that appear to be responsible for the trend, he noted.

The first is that women who become pregnant weigh more than they ever have, Gillman said, and "maternal body mass index is a determinate of infant weight at birth and after."

In addition, more mothers are putting on excess weight during pregnancy compared with decades past, Gillman said. "There is also an in crease in type 2 diabetes and gestational diabetes among mothers, which are determinants of infant weight at birth and after birth," he added.

How babies are fed may also play a role. "Infants that are breast-fed tend to gain weight more slowly than formula-fed infants," the Harvard expert said.


Gillman said early weight gain can have dire consequences for long-term health. Studies suggest that gaining excess weight during the first months of life is associated with becoming overweight and developing high blood pressure years later. Other data suggest that infants who gain excess weight are more likely to suffer from wheezing, which can lead to asthma, Gillman noted.

Expert Concerns About Obesity

One expert called the finding just one more facet of the ongoing obesity epidemic.

"This news is disturbing, but not surprising," said Dr. David L. Katz, an associate professor of public health and director of the Prevention Research Center at Yale University School of Medicine. "The progression from lean to overweight to dangerously obese occurs slowly, one pound at a time. The widely publicized increases in childhood obesity indicate that weight gain is beginning at an ever younger age. These data merely confirm the obvious," he said.

The message is troubling for several reasons, Katz said. "As weight gain becomes problematic earlier in life, other chronic disease can be expected to do the same. If overweight becomes commonplace among babies, heart disease may well become commonplace among adolescents, as type 2 diabetes is already," he said.

The nature of weight gain varies with age, Katz said. Infants and adolescents are far more adept at generating new fat cells than adults, he explained, and obesity caused by a high number of fat cells is harder to reverse than obesity caused by enlarging pre-existing fat cells.

"As difficult as weight control is for us, it will be that much harder, and more elusive, for our children," he said.

"The findings reported here are from a single HMO in one part of the country, but they contribute to an overwhelming body of evidence that childhood obesity is a crisis throughout the United States," Katz said.

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