Even babies are getting fatter.
A Harvard study, the first to document the spread of the obesity epidemic to infants, reported yesterday that Massachusetts children under age 6 have gotten heavier since 1980, but the risk of being overweight has jumped the most for babies under 6 months.
The findings, published in the journal Obesity, add to concerns that the growing number of children who are born heavy or gain weight quickly in early life are likelier to face future health problems, including obesity, diabetes, high blood pressure, and possibly asthma.
It may be time for Americans to give up the traditional idea that a fat baby is a healthy baby, said Dr. Matthew Gillman, the study's senior author.
``We no longer have grave threats to the lives of infants, such as diarrhea, other infections, and malnutrition," he said. ``Our problem in the 21st century is chronic disease, and as these overweight babies grow up, are they going to get asthma, stay overweight, develop high blood pressure and diabetes?"
Gillman and others also say that parents should not panic if an infant is heavy. Many lose their baby fat.
And breast-feeding has been shown to reduce the risk of infant obesity, said Dr. Wendy Slusser, a specialist in childhood obesity.
No definitive data have shown that being overweight as an infant means that a person will be overweight later on, said Slusser, an assistant professor of pediatrics at the University of California at Los Angeles.
But, she added, ``If we're seeing a trend of a population increasing in size, that does raise questions about the health habits of that population."
Since babies are usually fed only breast milk or formula until age 5 or 6 months, it seems unlikely that the new figures reflect poor food choices by parents.
Rather, the growing prevalence of obesity among the youngest babies may begin in the womb, said Dr. Laura Riley, medical director of labor and delivery at Massachusetts General Hospital.
``Pregnant women in general are more overweight these days," Riley said. ``More obese women become pregnant, and more women who are overweight when they become pregnant then gain too much weight during pregnancy."
In the past, Riley said, she has warned her patients that being overweight during pregnancy could lead to complications for the mother, including gestational diabetes and high blood pressure.
But the new study, she said, now allows her to say, ``If you overdo it during pregnancy, you're setting yourself up for a bigger baby."
And that means that ``you are setting your baby up for potentially a lifetime of weight problems," she said.
Obstetricians tend to recommend that normal-weight women gain between 25 and 35 pounds during pregnancy, while obese women should gain only 10 or 15 pounds.
The study defined overweight babies using federal growth charts meant for use by pediatricians. (Available at www.cdc.gov/growthcharts/).
In general, children were considered overweight if they fell in the top 5 percent on a measure that divides a child's weight by height.
They were considered at risk of becoming overweight if they fell between the 85th and 95th percentile.
For example, a 22-inch baby boy would be in the 95th percentile for weight if he weighed 12 1/2 pounds, according to the chart. A weight of 10 1/2 pounds would put a boy of the same length in the 50th percentile.
A different chart is used for girls, because their weight patterns are somewhat different.
The Harvard study mined data on about 120,000 children from birth to 6 years of age, using regular check ups from 14 Harvard Vanguard Medical Associates practices in Eastern Massachusetts.
Between 1980 and 2001, the years studied, the number of infants considered overweight rose by 74 percent, reaching a total of 6 percent of all infants studied. And the proportion of infants considered at risk of becoming overweight rose faster than any other age group in the study.
Overall, the study found that the percentage of children under age 6 who were overweight jumped from about 6 percent to 10 percent.
The study, which did not look at later health consequences of childhood obesity, found that the increase in weight was greater among girls than boys, and greater among Hispanic children than non-Hispanic black or white children.
Dr. Caroline Apovian, director of the Center for Nutrition and Weight Management at Boston Medical Center, said that some people will argue that a fat baby is nothing to worry about.
`Sure, a little fat on a baby is good," she said. ``But I think we're talking about a state of affairs that's gotten out of hand."
Much remains to be researched about the link between greater weight in infancy and later health consequences, said Gillman, an associate professor at Harvard Medical School.
Concerned mothers should avoid smoking during pregnancy because recent studies link smoking with weight problems during childhood, he said; they should try to head off excessive weight gain and diabetes during pregnancy; and they should do their best to breast-feed once the baby is born.
Researchers believe that breast-feeding teaches a baby to regulate its food intake better than bottle feeding.
``When we see that overweight is rising in our youngest children," he said, ``we need to think about obesity prevention efforts that start at the earliest stages of human development, even before birth."
Carey Goldberg can be reached at email@example.com.