Heaven-scent diet

If you're on a diet, having chocolate waved under your nose is torture. Nothing gets the tummy rumbling like a whiff of delicious treats. Aroma seems to be the ultimate appetite activator. But it's not, according to an American doctor who is turning the smells we love into a weapon in the war on flab.

Dr Alan Hirsch, a neurologist at the Smell And Taste Treatment And Research Foundation in Chicago, has developed calorie-free crystals infused with food scents that trick people into thinking they have eaten more than they actually have.

'It's your mind that decides when you're full,' says Dr Hirsch. 'And it doesn't do it by the amount of food in your stomach - if it did, people wouldn't overeat. It works it out through the mouth and nose. It tells itself: "I've smelled it, therefore I've eaten it, so I don't need any more."'

Flavour is a combination of taste and smell. As there are only five tastes, 90 per cent of flavour derives from smell, which is controlled by the olfactory nerve. It is this sense - not the taste buds or stomach - that is directly linked to the part of the brain that controls hunger.

Hirsch says this link can be used to deceive people's minds to make them feel fuller quicker. This is what his 12 scented crystals are designed to do. They come as sweet or salty. The sweet ones - cocoa, strawberry, banana, spearmint, raspberry and malt - are for sweet and neutral food, and the salty ones - taco, onion, ranch dressing, parmesan cheese, cheddar cheese and horseradish - are for everything else. They are used in a diet that allows you to eat whatever and whenever you want.

Results so far have been staggering.

A recent trial on a group of overweight people showed an average weight loss of more than two stone in six months.

No 'quick fix'

So is this a miracle cure for the obesity epidemic sweeping the Western world? Bridget McKevith, a nutrition scientist at the British Nutrition Foundation, says no.

'It's an interesting idea but, for the majority of people, there's never going to be one quick fix,' she says. 'People overeat for many reasons, and hunger is just one of them. This solution is unlikely to stop overeating resulting from anxiety, sadness or depression.'

Hirsch accepts there's a long way to go before the crystals will be on sale. 'We know they work on specific people,' he says. 'But we don't understand why yet. A lot more research is needed, and it will be at least five years before anything like this is available in stores.'

In the meantime, you can simulate the effects of the crystals by cooking with strong spices, garlic and aromatic fruits. Or, keep a bar of chocolate on hand at all times and, when temptation sets in, take three hearty sniffs then put it back in its wrapper until the next pangs arrive.