A 10-year study of over 65s has found a "striking" relationship between daily consumption of diet soft drinks and the size of your waistline.

Daily drinkers gained 8 centimetres of belly fat, compared to 2 centimetres  for non-drinkers and 4.6 centimetres for occasional users, over the total study period. The impact was most severe on those who were already overweight or obese.

Presenting their findings in the 2015 Journal of the American Geriatrics Society, the authors found that even when their body mass index (BMI) remained stable, daily drinkers of diet soda experienced "dramatically greater" waist circumference.

This is a pernicious form of weight gain, because belly fat is generally linked with higher levels of visceral fat (internal fat around the organs). This is in turn associated with greater rates of metabolic syndromes, diabetes and heart disease. And it doesn't take much to prompt negative health effects.

"Even small increases in abdominal obesity ... have been associated with significant increases in cardiometabolic risk factor levels," the study's authors wrote.

They recommended dietary advice for older people should include unsweetened coffee and tea, mineral water and minimally sweetened juice instead of diet soft drinks.

One reason for the damaging effect of diet sodas may be that artificial sweeteners aren't received in the same way by our bodies as natural sugars.

"Regular sugar has caloric consequences," the study's principal author, Helen Hazuda, told Time magazine - namely, it triggers a feeling of fullness.

"Your body is used to knowing that a sweet taste means you are ingesting energy in the form of calories that, if you don't burn them off, is going to convert to fat."

But artificial sugar doesn't have the same effect and actually confuses the body's link between sweetness and satiation, Professor Hazuda said.

The study first examined 749 European-American and Mexican-American men and women aged 65 and over, between 1992 and 1996. Follow-ups were undertaken in 2000-01, 2001-03 and 2003-04, and 71 per cent of survivors participated in the final follow-up.

Professor Hazuda, of the University of Texas, presented the preliminary results at a 2011 conference of the American Diabetes Association.

"Data from this and other prospective studies suggest that the promotion of diet sodas and artificial sweeteners as healthy alternatives may be ill-advised," she said at the time.

"They may be free of calories but not of consequences."

There have been numerous other studies that have cast doubt on diet soft drinks as a healthier option. One such paper, published in the April 2009 edition of Diabetes Care, found that drinking diet soft drinks daily was associated with a 67 per cent greater risk of having type 2 diabetes. Importantly, the study established a correlation between the two conditions, but not necessarily causation.

Another paper, published in the October 2014 edition of Nature, found that artificial sweeteners such as those used in diet drinks could induce and exacerbate glucose intolerance in both humans and mice.

And an observational study, published in the American Journal of Clinical Nutrition, suggested the consumption of both types of soft drinks was linked to higher rates of hip fractures in older women.