Lazy, shiftless couch potatoes of the world, here’s something to crow about. You may be able to enhance what little exercise you get, just by happily pondering the value of it.

In a novel investigation of the placebo effect and exercise, psychology researchers from Harvard University found that hard-working hotel housekeepers who were tutored on the fitness value of their tasks experienced marked health improvements. Within four weeks of learning that the physical demands of their daily tasks provided good exercise, the 44 room attendants lost an average of 2 pounds, lowered their blood pressure by almost 10 percent and logged statistically meaningful reductions in body mass index, body-fat percentage and waist-to-hip ratio, compared with the 40 housekeepers in the uninformed group.

Members of the informed group also perceived themselves as getting significantly more exercise than they had before, even though their workload and recreational exercise levels, as well as diet, remained constant.

Not everyone is buying the results.

“My first thought was, ‘When are they publishing it, April 1?'” says Patrick O’Neil, director of the Weight Management Center at the Medical University of South Carolina. “And I’m a clinical psychologist,” he adds. “These are my people.”

Lead author Alia Crum, now a predoctoral student at Yale University, acknowledges the provocative nature of the study, which is one of very few to test a placebo effect in exercise.

“It’s funny,” she says of the report, published in this month’s issue of Psychological Science. “Initially everyone was trying to discount it, saying, ‘Well, they just exercised more,’ because we have pretty firm notions of how to lose weight, and this is counter to those ideas.” But the results are not all that incongruent with studies on the placebo effect.

“We get stuck in the notion that you’ll lose a pound for every 3,500 calories – that weight loss is just a matter of what goes in and what goes out – and we forget about all the other components that might be involved, like our mindsets,” she says.

O’Neil believes the findings can be chalked up to something much simpler. “These results are more readily explained by the fact that the people in the informed group received more information related to health and exercise,” which led to undetected changes in activity level, he says.