Introducing the sitcom diet...

ATHENS (Reuters) - If you want to burn a few extra calories, laugh.

It's no match for running, cycling or pumping iron but scientists said Saturday laughing out loud for 10-15 minutes a day burns 10-40 calories, the amount in a small piece of chocolate, depending on a person's body weight.

"We calculated that this is equal to 2 kilograms (4.4 pounds) a year if you do it every day," Dr Maciej Buchowski, of Vanderbilt University Medical Center in Nashville, Tennessee, told an obesity conference Saturday.

Laughing makes people feel good and has been described as the best medicine. Buchowski believes he and his colleagues are the first to measure how much energy it takes to laugh.

"We discovered that laughter produces energy," he said.

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