Brazilian soccer star Ronaldinho Gaucho laughs at a training camp near Rio de Janeiro. (AFP)

Athens, June 4 (Reuters): If you want to burn a few extra calories, laugh.

It’s no match for running, cycling or pumping iron but scientists said today 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 kg a year if you do it every day,” Dr Maciej Buchowski, of Vanderbilt University Medical Center in Nashville, Tennessee, told an obesity conference today.

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.

They recruited 100 students who were friends or couples and measured the energy expenditure of each pair while they watched television comedy clips in a metabolic chamber. The sealed room enabled scientists to measure how much energy the laughter produced while a heart monitor also tracked their heart rate.

Buchowski and his team did not tell the students, who were advised not to talk or move. “It’s not easy to catch genuine laughter because if you tell people you are going to measure laughter they will force the laugh,” said Buchowski.

The scientists taped the students as they watched 10 minutes of comedy interspersed by 5 minutes of country scenes for an hour.