TUESDAY, June 22 (HealthDay News) -- Gaining weight when you're over age 50, especially around the waist, significantly increases your risk of type 2 diabetes, new research suggests.

Compared to people whose weight remained stable after age 50, people who gained the most weight after 50 (more than 20 pounds) nearly tripled their risk of developing type 2 diabetes, according to the study in the June 23/30 issue of the Journal of the American Medical Association.

"People over the age of 65 are at the highest risk of developing type 2 diabetes, and they have the highest rates of morbidity and mortality from heart disease, which can be related to diabetes. This is really a key clinic and public health issue," said study author Mary Biggs, a research scientist at the University of Washington in Seattle.

"We showed a strong relationship between increasing weight and waist circumference with the risk of type 2 diabetes," she said. "It's important as we get older to try to maintain an optimal weight."

Nearly 24 million Americans have some form of diabetes, according to the American Diabetes Association (ADA). Each year, more than 1.5 million Americans are newly diagnosed with the disease, according to the ADA. Most people who have diabetes have type 2 disease. Being overweight is a significant risk factor for developing type 2 diabetes, no matter what your age.

What hasn't been well-studied, according to Biggs and her colleagues, is how body composition and changing weight affects the risk of diabetes in older adults.

Using data from the Cardiovascular Health Study conducted from 1989 to 2007, the researchers reviewed information on nearly 4,200 people over the age of 65.

At the start of the study, none of the study participants had been diagnosed with diabetes. Statistics on body-mass index (BMI), waist circumference, waist-to-hip ratio and more were collected at the start of the study and over the course of an average of 12 years.

The researchers found that those with the highest levels of baseline measurements had a 4.3 times higher risk of diabetes than those with the lowest measurements.

And, certain measurements posed an even greater risk of diabetes. For example, men older than 65 with a BMI above 28.7 (25 to 29.9 is overweight, and above 29.9 is considered obese) had a 5.6 times higher risk of diabetes than someone with a BMI below 23.3. In women, the risk was 3.7 times higher, the study found.

Biggs said that although there was a difference between men and women, it didn't reach the level of "statistical significance" in this study. If such a difference holds up in further research, Dr. Loren Wissner Greene, an endocrinologist at NYU Langone Medical Center, said the difference would likely stem from the fact that men tend to have more fat around their mid-sections, which is a known risk factor for diabetes.

"Visceral fat more closely relates to insulin resistance, and women tend not to have as much visceral fat," she said.

Waist circumference was also strongly associated with risk of type 2 diabetes. In men, those with waists above 104.6 centimeters had 5.1 times the risk of diabetes, compared to their slimmer counterparts with a waist circumference of less than 89.1 centimeters. In women, the increased risk was 3.6 times higher for those with a waist circumference of 101.1 centimeters, compared to women with a waist measurement of 78.6 centimeters.

A changing weight over mid-life also had a significant impact on diabetes risk. In people who were normal weight at age 50, an increase of 13 to 20 pounds increased the risk of diabetes at age 65 or older by 1.3 times. If the weight gain was more than 20 pounds, the risk increased by 3.2 times.

The effect was even more significant for those who were overweight or obese at age 50, and who gained more weight. The researchers also found that the more weight the study volunteers gained, the greater the risk of diabetes.

"Weight gain increases the risk of diabetes at any age," said Greene.

Both experts recommended trying to keep your weight steady as you age.

More information

For advice on preventing weight gain, visit the U.S. Centers for Disease Control and Prevention.