THURSDAY, March 9, 2006 (HealthDay News) -- Breast-fed babies, so the prevailing wisdom goes, are less likely to have weight problems later in life. Introducing solid foods later -- at about four or six months -- is also thought to reduce the risk of being overweight later in childhood.
But the results of a new study question that wisdom, suggesting that bottle-fed infants aren't at higher risk for weight gain compared to their breast-fed peers.
"We found there were no differences in body fat [overall] at age 5 between breast-fed and formula-fed infants," said lead researcher Dr. Hillary Burdette, a nutrition specialist at The Children's Hospital of Philadelphia.
Her team also found no association between introducing solid foods earlier than recommended and excessive pediatric weight gain.
The findings are published in the March issue of the American Journal of Clinical Nutrition.
According to the American Academy of Pediatrics, exclusive breast-feeding is recommended for a child's first six months of life and then breast-feeding, supplemented by foods, is recommended up until 1 year of age. Solid foods are best introduced at 4 to 6 months of age.
"There have been lots of studies on [infant] feeding and obesity," but those studies "have had conflicting results," said Burdette, who is also an assistant professor of pediatrics at the University of Pennsylvania School of Medicine.
In their study, Burdette and her colleagues measured body fat levels for 313 5-year-olds while collecting data on each child's history of breast-feeding or formula. They also gathered data on the timing of the introduction of solid foods into the child's diet.
The team used a technique called dual-energy X-ray absorpiometry (DXA) to measure body fatness. Burdette noted that previous studies have focused on body mass index (BMI), a conventional measure of height related to weight, to determine fatness.
"What makes our study different is [that] we measured fatness directly, rather than using body weight or BMI," she said.
In the study, one-quarter of the mothers never breast-fed. Of the 231 who did, 88 did so for less than six months, 77 for six months to a year, and 66 for more than a year. Fifty-two of those women breast-fed for more than a year without using formula. Half of the mothers followed the recommendation for introducing solid foods at four months, and only 8 percent did not start feeding solids until age 6 months.
The researchers found no differences in fat levels between bottle-fed or breast-fed children, or in children who first ate solid foods earlier or later.
Burdette doesn't think her study will end the debate over links between infant feeding and overweight. And, she added, "the study doesn't suggest that the current recommendations need to be changed."
What her study might do, Burdette said, is ease the guilt of some mothers who aren't able to breast-feed or to breast-feed as long as is recommended. "Many mothers aren't able to breast-feed, for numerous reasons, either because they can't medically, or because of work," she said.
The study results are definitely "not a strike against breast-feeding," said Dr. Karen Hopkins, a clinical associate professor of pediatrics at the New York University Medical Center. The benefits of breast-feeding are well-documented, she said. "There's no added sugar or fat, no trans-fat" in breast milk, she pointed out. Studies have found breast milk protects infants from respiratory tract and ear infections, as well as improving their cognitive development, among numerous other benefits.
But, she questions whether the lack of an association between early solid food feeding and later overweight will bear out over time. Additional research is needed, she said, because "at least anecdotally it seems to be associated."
Hopkins advises parents to try to postpone giving infants solid foods for six months. "The reasoning is, you don't want to interfere with breast-feeding. And they don't need it [solid foods] physiologically," she said. "There is [also] a possibility they will gain too much weight too quickly. Early introduction of solid foods is also associated with the development of food allergies."
Breast-feeding is ideal, Hopkins said. But whether breast-feeding for the recommended time period is feasible "depends on what the patient's situation is," the NYU expert said.
"Say they are going back to work when the baby is 2 months. It is possible to pump [milk] but it is hard to do that, most workplaces are not set up for that. It takes about 20 minutes twice a day to pump milk, and you need a private place and someplace to store it," Hopkins said.
To learn more about breast-feeding, visit the American Academy of Pediatrics.