The free-electron laser heats up the fat which is then broken down and excreted by the body. Professor Rox Anderson, dermatologist at the Massachusetts General Hospital, led the experiment using pig fat and skin samples. He will tell the American Society for Laser Medicine and Surgery today that selective photothermolysis - heating tissues with light - could have a range of medical applications in the future.

Professor Anderson added: "We can envision a fat-seeking laser, and we're heading down that path now."