Reebok recently started selling a walking shoe, called Easytone, that is supposed to tone your leg and butt muscles while you walk.

And the buzz machine swung into action. The Easytone shoe has made a huge splash--TV appearances, newspaper and magazine articles, buzz, buzz, buzz.

If the shoe fits, does it really firm up those muscles? Does the Easytone shoe work?

Dan Ariely is James B. Duke Professor of Behavioral Economics at Duke University is skeptical. He points out that the scientific evidence is thin. Reports of Easytone effectiveness may, he speculates, may be due to the placebo effect. (Placebos are inert pills or any item that can't possibly be of direct medical benefit, but still makes people get better.)

The placebo effect is enormously important in medicine. When a new drug is tested on people and turns out to be effective, a notable number of people in the control group, who received a sham pill rather than the real thing, always get better too.

As it turns out, the placebo effect contributes heavily to the positive effects of exercise too. When people are told (falsely) that a particular activity is good exercise, many of them believe it so strongly that they lose weight and body fat and their blood pressure even goes down. Which has me wondering how I can convince myself that reading in bed, sleeping late, and taking long hot showers will make me thinner.