Saturday August 23 2008
What I particularly enjoy is the spectacle of fat people – ideally drinking beer – watching television, while somewhere on the other side of the world citizens of all nations are getting some nice exercise in the Olympics (throwing javelins, jumping over metal bars, climbing lamp posts with banners, and running away from the water cannon). These are the people I imagine paying for gyms they never visit, while I am cheerfully cycling to work and carrying the shopping up the stairs.
But can obsessing over sport actually improve your health? Slightly, possibly, if you’ve got something to work with.
Alia Crum and Ellen Langer from Harvard psychology department took 84 female hotel attendants in 7 hotels. They were cleaning an average of 15 rooms a day, each requiring half an hour of walking, bending, pushing, lifting, and carrying. These women were clearly getting a lot of good exercise, but they didn’t believe it: 66.6% of them reported not exercising regularly, and 36.8% said they didn’t get any exercise at all.
Their health, measured by things like weight, body fat, body mass index, waist-to-hip ratio and blood pressure, was related to their perceived amount of exercise, rather than the actual amount of exercise they got, and this, so far, isn’t very unusual. A classic study of 7,000 adults found that that perceived health is a better predictor of death than actual health, and another looking at elderly people found that those who perceive their health to be poor are 6 times more likely to die than those who perceive their health to be excellent, regardless of how healthy they actually are. Once again this goes to show the danger of relying on self-report data for health research.
But it gets better. Crum and Langer then divided the hotel workers into two groups (by hotel). One group got a one hour presentation on what a fabulous amount of exercise they were getting, how they were meeting and clearly exceeding the Surgeon General’s recommendations for an active lifestyle. They were given information sheets, in English and Spanish, showing the calorie burn for activities like vacuuming, or cleaning a bathroom, and the researchers even put notices up in communal areas explaining what excellently healthy exercise their work was.
The other group was left alone.
Four weeks later the researchers measured everything again. The group who had been tutored about the health benefits of their work now perceived that they did more exercise than before – unsurprisingly – while the group who were left alone didn’t change. Neither group had changed their actual levels of activity.
But amazingly, despite no change in actual exercise levels, in the intervention group, simply being told about the value of what they were already doing caused a significant change for the better on every single one of the objective health measures recorded: weight, body fat, body mass index, waist-to-hip ratio and blood pressure.
It’s an outrage. Maybe mindset alone can influence metabolism and the benefits of exercise: perhaps this experiment shows, essentially, the placebo benefits of exercise. Maybe the cleaners changed their behaviour, or their diets, in ways that the researchers didn’t pick up, perhaps they had more spring in their step, tipping the scales in their favour. And maybe it doesn’t actually matter what caused the change, as long as we can exploit it: because the links between body and mind are far more fascinating than any pill peddler would ever have you believe.
Crum AJ Langer EJ. Mind-Set Matters: Exercise and the Placebo Effect. Psychological Science 18(2) 165-171, 2007.
Kaplan, G.A., & Camacho, T. (1983). Perceived health and mortality: A nine-year follow-up of the Human Population Laboratory cohort. American Journal of Epidemiology, 177, 292–304.
Idler, E., & Kasl, S. (1991). Health perceptions and survival: Do global evaluations of health status predict mortality? Journals of Gerontology, 46 (2), S55–S65.