Type 2 diabetes occurs when the body's cells gradually lose their sensitivity to insulin; the illness is often linked to obesity.

Researchers from the University of Pittsburgh studied more than 2,200 women aged 40 to 78. They found that 27 percent of mothers who didn't breast-feed developed type 2 diabetes, almost double the rate among women who breast-fed or never gave birth.

The researchers say the differences between the groups held up even after they adjusted the statistics for factors such as age, race, levels of physical activity and body-mass index.

"Diet and exercise are widely known to impact the risk of type 2 diabetes, but few people realize that breast-feeding also reduces mothers' risk of developing the disease later in life by decreasing maternal belly fat," said Dr. Eleanor Bimla Schwarz, an assistant professor of medicine, epidemiology, and obstetrics, gynecology and reproductive sciences at the University of Pittsburgh, in a news release from the university.

"Our study provides another good reason to encourage women to breast-feed their infants, at least for the infant's first month of life," Schwarz said. "Clinicians need to consider women's pregnancy and lactation history when advising women about their risk for developing type 2 diabetes."

The study, which was funded by the U.S. National Institute of Diabetes and Digestive and Kidney Diseases and the National Institute of Child Health and Development, appears in the September issue of the American Journal of Medicine.

More information

There's more on breast-feeding at the U.S. National Library of Medicine.

SOURCE: University of Pittsburgh, press release, Aug. 27, 2010.

-- Randy Dotinga