If you drink diet soda thinking it will help you shed unwanted belly fat, nothing could be further from the truth, says a new study.

For the study, researchers gathered data on health status and lifestyles of 749 men and women aged 65 and older, and then tracked the health outcomes in 466 survivors for more than nine years.

The number of sodas they consumed — and whether they were diet or regular — was recorded at the beginning of the study and at each of three follow-up visits.

“Among participants, who reported that they did not consume any diet sodas, waist circumference increased less than one inch on average over the total follow-up period,” said lead author Sharon Fowler from University of Texas Health Science Center at San Antonio.

Among participants who reported occasional use — drinking less than one diet soda a day — waist circumference increased almost two inches.

And among those who consumed diet sodas every day, or more often than once a day, waist circumference increased over three inches.

These findings raise a red flag for seniors because fat around the waist — the proverbial tire around the middle — has been linked with increased inflammation and risk of metabolic disease, diabetes, heart attack, stroke, cancer and mortality.

When waistlines expand in older age, visceral fat increases disproportionately, and risk rises, the researchers noted.

The study appeared in the Journal of the American Geriatrics Society.