They are the calorie-free way of having a sweet treat, but diet drinks could still make you fat, scientists have warned.
A ten-year study of almost 500 men and women linked low-calorie soft drinks with bulging waistlines – even when taken in small quantities.
Those who downed two or more diet fizzy drinks a day saw their waistbands expand at five times the rate of those who never touched the stuff, a diabetes conference heard.
The results were so dramatic that the American researchers advise that people ditch their diet drinks and use water to quench their thirst instead.
Those who cannot bear to give up the sugar rush may be better off drinking normal full-sugar fizzy drinks.
Professor Helen Hazuda, of the University of Texas’s health science centre, said diet sodas and artificial sweeteners may foster a sweet tooth, distort appetite and even damage key brain cells. As a result, treating them as healthy alternatives may be ‘ill advised’
The professor, who no longer drinks diet colas and lemonades, said: ‘They may be free of calories but not of consequences.’
Professor Hazuda tracked the health and habits of 474 adults for an average of nine and a half years.
She then compared the growth in waistline of those who consumed diet drinks with the others, including some who only buy regular fizzy drinks.
Overall, those who favoured diet drinks saw their waists expand 70 per cent faster.
But ‘frequent users’ – defined as those who drink two or more cans a day – saw a 500 per cent greater increase in girth, the American Diabetes Association conference heard.
Significantly, the results still stood even when other factors such as exercise, social class, education and smoking were taken into account.
A second study, involving some of the same researchers and carried out on mice, linked sweetener aspartame with the sort of damage in the pancreas that can occur early in diabetes.
The researchers said they think that artificial sweeteners may distort appetite, leaving us craving extra-sweet and unhealthy treats.
They may also damage brain cells involved in feelings of fullness, while the lack of real sugar could also stop us from feeling full.
Professor Hazuda said that her study was the fourth large-scale piece of research to link diet drinks with ill health.
She added: ‘I think prudence would dictate drinking water.”