For the study, Levine and his colleagues developed a system that can detect the smallest tap of a toe -- high-tech underwear resembling bicycle pants and sports bras or T-shirts embedded with sensors, originally designed for fighter jets, that take measurements every half-second.
Ten men and 10 women, half of them lean and the other half mildly obese, wore the garments 24 hours a day for 10 days as they went about their usual routines. They went to the Mayo Clinic every morning to be weighed, get new undergarments so researchers could download the data from the previous day's undergarments, and get their meals for the day, so the researchers knew exactly what they were eating. All considered themselves "couch potatoes" because they eschewed regular exercise.
Based on millions of bits of data, the researchers determined that each day, the lean subjects spent at least 150 more minutes moving in some way than the obese subjects.
Next, the researchers overfed nine of the lean subjects and put seven of the obese subjects on diets to see if losing weight would make the obese more fidgety, or if gaining weight would make the lean less active. They then monitored them for another 10 days.
"It could be the obesity was making the difference -- not the other way around. We thought, 'Well, in that case if they lost weight they'd start standing more, and surely then if they got heavier they'd gravitate to their chairs more,' " Levine said. "Neither of these things happened. The obese person remained a sitter, and the lean person remained a stander."
Other research has indicated that some people may be born with a predisposition to move while others are born the opposite.
"There may be brain chemicals driving obese people into their chairs or driving lean people out of them," Levine said.
As society and technology have made it easier for sitters to sit, that inclination has been exaggerated, which could help explain a large part of the obesity problem, Levine and others said.
"We all know what it's like to like and dislike different things. . . . Since the environment has become more and more friendly to being sedentary, people with that predisposition to respond to those cues are likely to become obese," Levine said.
The findings should encourage efforts to create an environment that makes it easier for people to get moving, he said. In the meantime, individuals should be encouraged to move more on their own.
"We can begin to say to people, 'Yes, it would be good if you went jogging, and it would be good if you went to the gym. But it's also good to keep getting up, moving around.' Fidgeting and doing all those small things will make a difference," said Paul Trayhurn of the University of Liverpool in England.
