It sounds just too good to be true - cakes and chocolate bars that help you burn off calories, courtesy a tasteless extract from chilli peppers.

This "miracle" extract, known as dihydrocapsiate (DHC), speeds up the body's metabolism, helping it use up more calories. It is already sold in the form of diet supplement pills in the US and Japan, but it could be about to be used as a food additive in Britain, the Daily Mail reports.