The calorie-free version fails to activate a reward area of the brain (Image: Patrick Norman/Fancy/Plainpicture)

CONTAINS zero calories! Countless soft drinks are emblazoned with that slogan as a come-on for those of us locked in a never-ending battle to rein in a spreading waistline. Calorie-free sweeteners certainly have a lot to offer. Food and drink manufacturers have become so good at blending sugar substitutes into their products that it can be almost impossible to tell them apart from the real thing – sucrose – in taste tests.

But while artificial sweeteners may be able to confuse our taste buds, the suspicion is growing that our brain is not so easily fooled. Could it be that our cravings for sugary foods run deeper than a liking for sweetness? If so, a whole bunch of weight-loss strategies may need rethinking.

Non-sugar sweeteners have come a long way. One of the first, and perhaps the worst, was lead. Romans boiled grapes in lead pots, leaching the sweet-tasting metal into their food. The practice outlived the Roman empire by many centuries, and is thought to have led to the deaths of a number of notables, including Pope Clement II, who perished in 1047. Indigenous peoples in South America use a herb called stevia, which contains chemicals that taste sweet but aren’t metabolised in the human gut. These early experimenters weren’t worried about shedding the kilos – just searching for a way to sweeten food in a world where refined sugar was scarce.

Saccharin, the first of the industrially manufactured artificial sweeteners, was discovered late in the 19th century and soon became popular. Taxes and restrictive patents kept …