Stockholm: A drug derived from the saliva of a monster lizard reduces the craving for food, including chocolate, said researchers after testing it successfully on rats.

An increasing number of patients suffering from type 2 diabetes are offered a drug called Exenatide, which helps them control their blood sugar. It is derived from a natural substance called exendin-4, obtained from the saliva of North America's largest lizard Gila.

Researchers at the Sahlgrenska Academy in University of Gothenburg have now found an entirely new and unexpected result of the lizard substance, the Journal of Neuroscience reports.

In a study with rats, Assistant Professor Karolina Skibicka and her colleagues show that exendin-4 effectively reduces the craving for food. "This is both unknown and quite unexpected effect," said Skibicka, according to a Gothenburg statement.

"Our decision to eat is linked to the same mechanisms in the brain which control addictive behaviours. We have shown that exendin-4 affects the reward and motivation regions of the brain," said Skibicka.

"Most dieting fails because we are obsessed with the desire to eat, especially tempting foods like sweets. As exendin-4 suppresses the craving for food, it can help obese people to take control of their weight," said Suzanne Dickson, professor of physiology at Sahlgrenska.

"It is the same brain regions which are involved in food and alcohol craving, so it would be very interesting to test whether exendin-4 also reduces the craving for alcohol," said Skibicka.