Giggling for just 15 minutes a day burns enough calories to shed up to 5lbs of fat over a year, work shows.
Laughter burns calories
A big belly laugh uses about the same energy as walking more than half a mile, the US study in the International Journal of Obesity suggests.
Laughing makes the heart beat faster and works many different muscles.
The researchers measured the number of calories expended by 45 adults as they watched different TV programmes, including nature and comedy shows.
Bouts of laughter when watching the funny film used up to 20% more energy than at rest.
This would mean that 10 to15 minutes of laughter a day could increase total energy expenditure by 40 to 170 kJ or burn off between 10 and 40 calories, the researchers estimate.
Lead author Dr Maciej Buchowski, from Vanderbilt University in Nashville, Tennessee, explained: "Participants had 10 to 20 percent higher energy expenditure during episodes of laughter than during rest.
"We have calculated that the energy cost of 15 minutes of laughter over one year may translate into annual weight loss of 4.5lbs."
Work already suggests that laughter is good for the heart and immune system, and appears to help ease pain.
Dr Shevach Friedler at the Assaf Harofeh Medical Centre in Zerifin even found humour increased the chance that fertility treatment would be a success in patients seeking IVF.
He said: "Laughter has a physiological effect as well as a psychological one.
"It is an intuitive human trait. We do not learn it. It's in our genes.
"If we retain this in our genes then probably it has beneficial effects."
He said it was likely that more research would uncover many more health benefits linked to laughter.