TUESDAY, July 21, 2015 (HealthDay News) -- Your risk for type 2 diabetes might be affected by both your birth weight and your lifestyle, a new study suggests.
"We found that both low birth weight and unhealthy lifestyle were associated with a significantly higher risk of type 2 diabetes," study leader Dr. Lu Qi, associate professor of nutrition and epidemiology at Harvard School of Public Health in Boston, and colleagues said in a news release from the journal BMJ, which published the findings July 21.
What's more, the effect was largest for people who had a low birth weight and also had unhealthy adult lifestyles, Qi's team found.
Just how would being born underweight influence a person's risk for type 2 diabetes much later in life? One expert not connected to the study said it may be due to what's known as the "thrifty gene hypothesis."
The theory holds that "poor fetal growth leads to metabolic adaptations made by the fetus in a [uterine] environment with limited amount of nutrients," explained Dr. Patricia Vuguin, a pediatric endocrinologist at Cohen Children's Medical Center in New Hyde Park, N.Y.
However, when the person grows up to find themselves surrounded by lots of high-calorie, fattening foods, "the body cannot adapt and develops chronic diseases such as type 2 diabetes," she explained.
The Harvard study included nearly 150,000 healthy men and women whose health and behaviors were followed for between 20 and 30 years. The researchers looked at the participants' birth weight, and they also assessed how healthy their lifestyles were, based on five factors: diet, smoking, physical activity, alcohol use, and body fat.
During the follow-up period, more than 11,700 new cases of type 2 diabetes were diagnosed among the participants.
The study wasn't designed to prove cause and effect. However, according to Qi's group, there were consistent associations between low birth weight and diabetes risk, and between unhealthy lifestyle and diabetes risk, and a significant interaction between the two factors together and diabetes risk.
This suggests that some cases of type 2 diabetes depend on a person having both early life factors (such as being underweight at birth) and later-life factors such as lifestyle, the researchers said.
"The findings suggest that most cases of type 2 diabetes could be prevented by the adoption of a healthier lifestyle, but simultaneous improvement of both prenatal and postnatal factors could further prevent additional cases," Qi's team concluded.
Vuguin agreed, saying that it's likely that preventing diabetes "through the promotion of a healthy diet should be a priority, especially for the people who were exposed to a poor environment during fetal life."
Another expert said the problem is only likely to get worse. "With the obesity epidemic worldwide, even in adolescents, we now have a 'double whammy' [low birth weight and lifestyle] causing increased obesity and diabetes in adults," said Dr. Derek LeRoith, professor of diabetes at the Icahn School of Medicine at Mount Sinai in New York City.
The U.S. Office of Disease Prevention and Health Promotion explains how to prevent type 2 diabetes.