Thin folks who tap their toes while they work and fiddle during routine activities could be burning hundreds more calories a day than plumper couch potatoes.

Researchers at the Mayo Clinic in Minnesota designed a study to test if some people are born to stay seated while others are restless enough to make themselves thinner.

They found obese people sat for about 150 minutes more per day on average compared to lean subjects, who burned 350 more calories daily.

Everyday activity adds up.

The naturally leaner subjects didn't necessarily sweat more at the gym. They simply were active, whether cleaning the house, walking to work or twiddling their thumbs at "non-exercise activity thermogenesis," or NEAT.

The study's lead author, endocrinologist Dr. James Levine, explored links between inactivity, low metabolism and obesity in the hopes of devising new treatments for obesity.

"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," said Levine.

For Levine, the results suggest if people can return to the activity levels of the 1950s then the U.S. has the potential to trim expanding waistlines.

Standers versus sitters

In the experiment, 10 lean subjects and 10 healthy, mildly obese adults (BMI of 33 or higher) wore customized undergarments embedded with sensors that monitored their posture and movements every half second, 24 hours a day for 10 days.

The participants had to eat all of their specially prepared meals at the hospital, with no home-cooked treats or restaurant food allowed. Investigators performed special metabolic tests on them.

They found obese participants sat or lay down an average 2.5 hours more per day than their lean counterparts. On the other hand, burning more NEAT calories could translate into 33 fewer pounds over a year, the researchers said.

The lean volunteers were then fed an extra 1,000 calories to see if they'd become more sedentary, but they didn't.

And obese volunteers who shed pounds continued to prefer the couch instead of being active, such as using a treadmill while watching TV.

The study appears in Friday's issue of the journal Science.