TUESDAY, May 15 (HealthScout) -- Two new studies say breast-feeding may reduce the chance that a baby will become a fat adult, but not as much as other studies have suggested.
An earlier German study, which said breast-fed babies were 30 percent less likely to become overweight adults than bottle-fed babies, prompted one of the two new studies, which are reported in this week's Journal of the American Medical Association (JAMA).
One new study, led by Mary L. Hediger, a biologist at the National Institute of Child Health and Human Development, looked at data on 2,685 children, ages 3 to 5, enrolled in the third National Health and Nutrition Examination Study.
The data indicated that breast-fed children had a 16 percent reduced risk of becoming overweight -- not an overwhelming factor, Hediger says. "Breast-feeding may play a small role in preventing overweight, but not enough to make a major impact," she says.
The study did point to a more important influence, she says: "The biggest factor in being overweight in early childhood is maternal overweight. It's probably a combination of genetic and environmental factors."
Hediger says being overweight in the first years of life does not necessarily predict obesity later in life, but "the concern is that chubby children turn into chubby adolescents who turn into chubby adults."
The second study reported in JAMA examined that possibility. A team led by Dr. Martin Gillman, associate professor of pediatrics at Harvard Medical School, analyzed questionnaires filled out by more than 15,000 adolescents, ages 9 to 14, in the Growing Up Today Study. About 5 percent of the girls and 9 percent of the boys were overweight.
After accounting for such factors as the mother's weight, physical activity and television watching, the researchers found that about 22 percent fewer breast-fed children were overweight compared with bottle-fed children. "In addition, the apparent [weight] protective effects were larger with increasing duration of breast-feeding," the researchers say.
Several explanations are possible, says Laurence Gummer-Strawn, chief of the Maternal and Child Nutrition Branch of the Centers for Disease Control and Prevention (CDC). One is that the amount of milk a mother can produce is limited, so that by switching to formula, "a natural method for control is squelched."
Gummer-Strawn say another possibility is that the hormonal response to formula is different than the response to breast milk, so that more calories in formula are stored as fat. Breast-feeding also may affect eating habits later in life, making acceptance of a diverse diet more likely, he says.
"Breast milk changes during the day, which can affect a child's willingness to accept new foods. If you give children a food they have never had before, a breast-fed child is more willing to accept it than a formula-fed child," Gummer-Strawn says.
All in all, he says, "This [study] is one more reason to breast-feed. I don't think it alone will change people's minds, but it is one more to add to the list."
What To Do
"Elimination of the barriers that lead to the early termination of breast-feeding must become high priorities," says a statement by Dr. William H. Dietz, director of the CDC's Division of Nutrition and Physical Activity. He says, "Work site facilities and policies that allow mothers to continue to provide breast milk after returning to work may represent one of the policy shifts necessary to help address the obesity epidemic."
For more on breast-feeding, check the American Academy of Pediatrics.
Or, read previous HealthScout stories.