Chili and capsicum may switch on metabolism, helping people lose weight, a leading Australian cardiologist says.

David Colquhoun, of the University of Queensland, said early evidence suggested the capsaicin found in the peppers should form part of a healthy, weight-reducing diet.

"There's some evidence that it tends to turn on metabolism and help people decrease weight," he said.

"It's not a magic cure, but it may aid weight loss. We need some more trials; it won't cause any harm, and it may just help a little."