People who cannot sit still for more than a few minutes provide a clue to keeping slim and trim, a US study says.
Some people may be prone to obesity, say scientists
The Mayo Clinic team says some people have a biological need to fidget and, as a result, burn more calories.
They used technology embedded in pants to log even the smallest movements of 10 obese and 10 lean volunteers.
The team told Science Magazine that the calories people burned in everyday life were more important in determining weight than previously thought.
While fidgeters burn off the calories, couch potatoes can pile on the pounds, they said.
The technology was based on that used in fighter-jet control panels, and allowed the scientists to monitor body postures and movements every half-second, continuously for 10 days, from the volunteers' undergarments.
The study participants were asked to go about their normal daily routines while wearing the undergarments for the first 10 days of the study.
The Mayo team entered this data into a computer, along with the subjects' weights.
For the second part of their experiment they asked 10 volunteers who were overweight and 10 who were lean to eat special diets.
The lean volunteers were overfed by 1,000 calories per day to make them gain weight. The obese volunteers were underfed by 1,000 calories per day.
The volunteers' activity over the following 10 days was logged for comparison with the earlier results.
Even after gaining weight, the naturally lean group was more active than the other group.
The obese volunteers sat for, on average, 150 minutes more and burned 350 fewer calories each day than the naturally lean volunteers.
Dr James Levine, lead author, attributes their findings to something called NEAT - non-exercise activity thermogenesis.
"A person can expend calories either by going to the gym or through everyday activities.," he said.
The undergarments worn in the study detect the smallest movements
"Our study shows that the calories that people burn in their everyday activities - their NEAT - are far, far more important in obesity than we previously imagined."
David Haslam from the National Obesity Forum said: "There does seem to be some truth in it.
"If you are making a cup of tea and pacing up and down you will be using more calories than if you are standing still.
"Fidgeting is a good thing. It's not a bad habit like picking your nose. The big question is can we use it to help overweight patients?
"Can we teach someone to fidget?"
Claire Mac Evilly, from the Medical Research Council's Human Nutrition Research, said it was a very small study and doubted whether you could teach people to fidget.
"It's just too difficult. It would take quite a big change to their normal habits," she said.
"Plus we don't know whether being overweight is a cause of someone being less active or a consequence.
"Certainly small changes can help, like getting off the bus one stop before yours and taking the stairs rather than the lift.
"The best advice is to eat healthily and exercise regularly."