You would think the growing use of artificial sweeteners and diet sodas over the past 30 years would have made a dent in the obesity epidemic, but they haven't. Why not? After all, they contain no calories.

On any given day, about one-fifth of the US population drinks a diet drink, and older adults are more likely to do so than younger adults.

Occasional diet soda drinkers’ waist size increased 1.83 inches, and those who drank diet soda daily over the course of the study saw an increase of 3.16 inches in their waistline.

Years of chronic diet soda consumption may actually increase belly fat and the odds of developing metabolic syndrome and cardiovascular disease, according to a recent study.

Nearly 800 white and Latino adults, aged 65 and older, enrolled in the San Antonio Longitudinal Study of Aging (SALSA) between 1992 and 1996 and were followed for over nine years. Their intake of diet soda was measured in addition to their waist circumference, height, and weight at enrollment and again in three follow-up visits.

Those who did not consume diet soda at all had an increase in their waist size of .80 inches over the course of the study. Occasional diet soda drinkers’ waist size increased 1.83 inches, and those who drank diet soda daily over the course of the study saw an increase of 3.16 inches in their waistline.

“Our study seeks to fill the age gap by exploring the adverse health effects of diet soda intake in individuals 65 years of age and older. The burden of metabolic syndrome and cardiovascular disease, along with healthcare costs, is great in the ever-increasing senior population,” researcher Sharon Fowler explained in a statement.

“The SALSA study shows that increasing diet soda intake was associated with escalating abdominal obesity, which may increase cardiometabolic risk in older adults,” she concluded.

So people who drink a lot of diet soda are big around the middle; but is it really diet soda causing the problem? Perhaps they consumed more of a lot of things, many of them calorie-filled?

Because this study was observational in nature, it does not prove diet soda is the cause of increasing pants size. Also, there are newer artificial sweeteners and blends of artificial sweeteners that can sweeten products using tiny amounts of artificial sweeteners that weren’t available at the time of this study.

Several research studies over the past few years have cast a shadow over the safety of diet sodas, but none has definitively proved a cause and effect with any disease or health condition.

If nothing else, this study serves as a reminder that too much of a good thing may be bad. Diet soda lovers may want to curb their intake or find other alternatives to satisfy their craving for bubbly carbonation until the question of diet sodas’ safety is answered once and for all.

The study is published in the Journal of the American Geriatrics Society.