CURLING up with laughter has similar effects on the body as pumping iron in the gym, a study has shown.
Sessions of mirthful laughter – dubbed "laughercise" by researchers – enhance mood, reduce stress hormones, boost the immune system and lower blood pressure and levels of "bad" cholesterol, researchers have found.
Like physical exercise, they also appear to stimulate appetite, offering a potential way to help malnourished patients who are off their food.
Laughter has long been thought of as the "best medicine" but recent research has shown that it really can have health benefits.
Previous research by US scientists led by Californian physician Dr Lee Berk has demonstrated how laughter improves mood, reduces stress and activates immune system cells, especially those which combat cancer.
Laughter has also been shown to benefit blood pressure and cholesterol levels.
The latest study from Dr Berk's team suggests that some of the effects of laughter mirror those of repetitive exercise.
During a three-week investigation, 14 healthy volunteers were asked to watch two 20-minute videos designed to be either distressing or humorous.
The distressing clip consisted of the first 20 minutes of the Second World War movie Saving Private Ryan, showing American troops being cut down by enemy fire as they storm Omaha Beach in Normandy.
For the "laughter" video, volunteers were given a variety of options including performances by stand-up comedians and scenes from comedy movies. They were allowed to choose clips that most appealed to their individual sense of humour.
Each participant sat through both videos with a week's gap in between to ensure their effects did not overlap.
The researchers took measurements of blood pressure and carried out blood tests to check levels of two appetite hormones, leptin and ghrelin.
No significant effect on the hormones was seen after volunteers viewed the distressing video. But watching the humorous clip both caused changes in blood pressure and led levels of leptin to decrease as those of ghrelin went up.
Similar effects are seen straight after moderate physical exercise, and are accompanied by an increase in appetite.
Dr Berk said: "The ultimate reality of this research is that laughter causes a wide variety of modulation, and that the body's response to repetitive laughter is similar to the effect of repetitive exercise.
"The value of the research is that it may provide healthcare providers with new insights and understanding."
Many elderly patients suffer from "wasting" due to reduced appetite, as a result of depression and lack of physical activity.
Such patients may be able to use "laughercise" to help them regain their appetite, say the scientists.
LEADING a couch potato lifestyle, including smoking, drinking and eating unhealthy food, triples your risk of dying from cancer or heart disease.
A study found that the combination of four unhealthy behaviours – smoking, lack of exercise, poor diet and alcohol use – combined to substantially increase the risk of death.
Leading this kind of unhealthy lifestyle could give you the same risk of dying as someone, on average, 12 years older than you, according to the study in Archives of Internal Medicine.
Campaigners yesterday said that the findings showed the importance of making lifestyle changes to improve health.