If you thought diet soft drink was a healthy alternative to the regular, sugar-laden stuff, it might be time to reconsider.

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 users of diet soft drinks gained nearly 8 centimetres of belly fat over the course of the study. Credit:Daniel Acker

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.