Phytopharm initially worked with Pfizer on bringing hoodia to market. In 2002, a trial on 30 obese adults showed that the intake of people given the p57 extract dropped by 1,000 calories a day. But after spending around $25m (£14.4m) Pfizer dropped their work on the plant. Pfizerwanted to put p57 into a pill, but the extract was too complex to make artificially. In late 2004, Unilever stepped in, and in a £21m deal, said that it intended to commercially grow hoodia, an endangered plant in its native South Africa, and use the extract in its slimming foods.

While p57 holds plenty of promise to help people regulate weight without having to resort to pharmaceuticals, Prof Blundell said that, as more of the mysteries of appetite regulation are cracked, more targets for treatments will become apparent.

Recently a new hormone was discovered that seems to suppress appetite - obestatin. "It's clear that there are many molecules floating around in our bodies doing things with some functional properties that we haven't yet discovered," said Prof Blundell.

For scientists trying to work out how to curb the obesity problem, a product that can be simply added to food may have immense value.