The sweetener interferes with the body’s glucose tolerance, a forerunner of diabetes, and also increases a person’s BMI (body mass index), an indicator of body fat.

Aspartame seems to alter the make-up of the gut, and affects its ability to control blood-sugar (glucose) levels, says Prof Jennifer Kuk at York University in Canada. Excess insulin production, used to control glucose levels, results in weight gain, and eventually obesity, and both of these are often a precursor of diabetes itself.

She tested the effects of aspartame on a group of more than 2,500 adults participating in the Third National Health and Nutrition Survey. The sweetener was monitored alongside naturally-occurring sugars, such as fructose from fruits.

Those who regularly consumed aspartame were less able to maintain stable glucose levels naturally than were those who consumed saccharin or fructose.