April 27, 2010 (Anaheim, Calif.) -- A hearty laugh and a moderate workout may have more in common than anyone thought.
Both affect the appetite hormones in much the same way, says Lee Berk, DrPH, MPH, director of the molecular research laboratory at Loma Linda University in Loma Linda, Calif., and a longtime researcher on the benefits of laughter.
''The parallel between moderate exercise and mirthful laughter is uncanny," Berk tells WebMD.
But he's clear from the start: "You can't increase leg muscle strength by sitting and laughing."
But he does think laughter, already linked with reducing stress and heart disease risk, as well as other benefits, may help improve appetite in those who have lost theirs due to disability or age. And it may improve wellness for the rest of us.
Laughter, Workout Link
In previous research, Berk has found that ''mirthful laughter'' reduces the stress hormones known as cortisol and catecholamines, much the same way that moderate physical exercise does.
In the new study, Berk evaluated the effects of a good belly laugh on two hormones that regulate appetite: leptin and ghrelin.
"When leptin goes down, it increases appetite," Berk says. "When ghrelin goes up, it increases appetite.''
That is what typically happens after moderate exercise, he says.
To test the effects of exercise on these hormones, he showed 14 healthy volunteers, average age 21, 20-minute segments of two different videos.
One was humorous, and the participants selected one depending on their preference. Choices included videos with Bill Cosby, Jeff Foxworthy, Will Ferrell, and others.
He also showed them a video meant to be stressful to watch, the 1998 movie Saving Private Ryan, a graphic World War II movie.
The participants watched the videos in random order. They gave blood to assess their leptin and ghrelin levels a week before the study, immediately before viewing, and immediately after viewing the videos. The hormones were measured well before viewing, Berk says, to rule out the well-known anticipatory effect.
Laughter, Workout Study Results
After watching the funny videos, participants had a decrease in leptin of about 15%, Berk found. After watching the war movie, there were no significant changes in the hormone.
They had an increase in ghrelin after viewing the humorous video of about 9%, he found, but no change after the war movie.
The results don't mean that laughter increased appetite, he says, but rather that the body's response to repetitive laughter is similar to that of repetitive workouts.
Laughter, Workout Study: Implications
Berk hopes the research may help elderly people who have lost their appetite, whether due to depression, illness, or lack of physical activity.
''The second application is for wellness," he says. Laugh while you work out, he suggests, and you may just be tuning up your appetite hormones, keeping them in balance, as well as improving your cardiovascular fitness.
The research, he says, may help those who have difficulty getting in physical activity, such as those who are physically handicapped or elderly.
Cautioning that the study is small and the results preliminary, Mary Bennett, PhD, director of the Western Kentucky University School of Nursing in Bowling Green, says the results are interesting.
She has researched and published on the value of humor and laughter and reviewed the new study findings for WebMD.
"It looks like it is possible that a brief period of laughter affects the hormones that control appetite in such a way that it might improve appetite," she tells WebMD.
That, in turn, might be helpful, she says, for the elderly who have so little appetite they are losing weight.
But she offers a caveat, too: "We don’t know the dose of laughter or how often the dose needs to be applied to make a real difference in people's health," she says.
Even so, she adds, she's not suggesting avoiding laughter at all; she endorses enjoying a good laugh whenever possible.