Two new studies have linked drinking diet soda to poorer health compared with those who don't drink the beverage.
People who said they drank two or more diet sodas a day experienced waist size increases that were six times greater than those of people who didn't drink diet soda, according to researchers from the University of Texas Health Science Center at San Antonio.
A second study that found the sweetener aspartame raised blood sugar levels in diabetes-prone mice.
"Data from this and other prospective studies suggest that the promotion of diet sodas and artificial sweeteners as healthy alternatives may be ill-advised," said study researcher Helen P. Hazuda, professor and at the university's school of medicine. "They may be free of calories, but not of consequences."
The human study was based on data from 474 participants in a larger, ongoing study called the San Antonio Longitudinal Study of Aging. In that study, the participants were followed for nearly 10 years.
Diet soft drink drinkers, as a group, experienced 70 percent greater increases in waist circumference compared with those who don't drink diet soda. [Related: 5 Experts Answer: Is Diet Soda Bad for You?]
Abdominal fat is a major risk factor for diabetes, cardiovascular disease, cancer and other chronic conditions, the researchers said.
In the mouse study, researchers fed aspartame, a calorie-free sweetener used in some diet sodas, to diabetes-prone mice. One group of mice ate chow to which both aspartame and corn oil were added; another other group ate chow with only corn oil added.
After three months, the mice that ate aspartame showed elevated blood sugar levels.
"These results suggest that heavy aspartame exposure might potentially directly contribute to increased blood glucose levels, and thus contribute to the associations observed between diet soda consumption and the risk of diabetes in humans," said study researcher Gabriel Fernandes, professor of rheumatology and clinical immunology at the university.
The studies were presented Saturday (June 25) at the meeting of the American Diabetes Association.
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This story was provided by MyHealthNewsDaily, sister site to LiveScience.