So do they have a place in our shopping baskets?

“A lot of people presume they must be healthy options since they are not sugared beverages, but the critical thing for people to understand is we don’t have the evidence, ” said Prof Susan Swithers, from the U’Ss Purdue University.

Studies looking at large groups of people have shown obese people tend to drink more fizzy diet drinks than those of a healthy weight.

A study of US adults in the American Journal of Public Health showed 11% who were a healthy weight, 19% of those who were overweight and 22% who were obese drank diet beverages.

And a study in the journal Obesity that followed 3,700 people for eight years showed those devouring the low-calorie sweeteners put on the most weight.

The researchers were left asking the question: “Are artificial sweeteners fuelling, rather than struggle, the very epidemic they were designed to block? “

But it is impossible to ascertain cause and effect in such studies. Are the drinks causing weight gain or are obese people turning to diet drinks in an effort to control their weight?

Different types of sweetener

Image copyright SPL

Aspartame: Odourless, white crystalline powder that is derived from two amino acids Saccharine: The first artificial sweetener ever synthesised in 1879 Stevia: Sweetener derived from the South American Stevia plant