SAN ANTONIO, Texas -- There's a new twist in the debate over diet soda.
It's not just a question of whether you'll gain weight drinking it.
In a new study published in the Journal of the American Geriatrics Society, older adults who drink diet soda daily gained almost three times as much belly fat over a decade as those who didn't drink diet soda.
Even among those who only drank diet soda occasionally, the increase was more than double that of those who did not drink diet soda.
"The more people drank diet sodas, the more their waistlines expanded," said study author Sharon Fowler, a researcher at the University of Texas Health Science Center at San Antonio.
Fowler's previous research established a link between diet soda and weight gain.
Over the new nine-year study, the average increase was 1.83 inches among those who drank diet soda occasionally, and 3.16 inches among those who drank it daily.
The waist size of the people who didn't drink any soda increased by an average of 0.8 inches. according to the study.
The study was done with 749 Mexican Americans and European Americans who were 65 or older when the study started.
The researchers asked them about their soda intake every few years, and how many were diet or not.
Their waist circumference, height and weight were measured when the study began, and at three follow-up points during the study period.
Increased belly fat, which is usually what causes increased waist circumference, can increase the risk of cardiovascular disease and other health issues because it increases inflammation, Fowler said.
The new study adds to a growing body of research on the potentially harmful effects of diet soda on human health.
In a 2011 study presented at the American Stroke Association's International Stroke Conference, researchers found that people who drink diet soda every day may have an increased risk of stroke and heart attack.
A study published in 2012 in the Journal of General Internal Medicine also found a link between daily diet soda consumption and stroke, heart attack and death.
And research presented at the American Academy of Neurology's 2013 annual meeting found a link between drinking diet soda daily and an increased risk of depression.
In the new study, the researchers said what might connect diet soda consumption with an increase in waist circumference.
But it may have something to do with the sweeteners used in diet soda, and the way they may affect food-intake regulation, Fowler said.
Fowler suggested diet soda drinkers try to reduce or quit, considering its potential negative effects on health.