The LOL Diet

It may not be as good for reducing the waistline as going to the gym or resisting that ice-cream sundae, but American researchers have found that 10-15 minutes of genuine giggling can burn off the number of calories found in a medium square of chocolate. The findings on the weight-loss possibilities of the uniquely human experience of laughter were presented at the close of the annual European Congress on Obesity on Saturday.

Researchers at Vanderbilt University in Nashville, Tennessee, recruited 45 pairs of friends, shut them in a room decorated like a cheap hotel -- scientifically known as a metabolic chamber -- played them comedy clips on a TV screen and measured how many calories they burned when they laughed.

The room was specially designed so the scientists could measure how much oxygen the volunteers inhaled and how much carbon dioxide they exhaled -- the gold standard for measuring energy burning. Noting differences in the oxygen and carbon dioxide patterns before and during laughter allowed the scientists to calculate whether laughter used more energy and how big the difference was. The heart rate, laughter and breathing information was then lined up in the special laughter lab and the tapes were analyzed second-by-second.

"They burned 20 percent more calories when laughing, compared to not laughing," Buchowski said. "Then we calculated what would happen if somebody laughed for 10 or 15 minutes a day and we found that it was up to 50 calories, depending on your body size and the intensity of the laughter."

That means that if you laugh for 10-15 minutes a day, you'd burn enough calories to lose two kilograms (4.4 pounds) in a year, Buchowski said.