Squirming in your seat, scratching your head and generally changing your posture frequently can burn as many calories as strolling for 15 minutes every hour, the scientists found. In an eight-week study, 16 volunteers were fed the equivalent of two large burgers a day on top of their normal food needs, while taking very little exercise.
Their weight gains were measured and the scientists found that the people who had fidgeted the most were the ones who had suffered the smallest increase.
The scientists found that for every 1,000 extra calories consumed by the volunteers, 39 per cent ended up as fat, but up to 33 per cent was burnt off by "Neat", an acronym for "non-exercise activity thermogenesis", or, in layman's terms, fidgeting. "Those people who had the greatest increase in Neat gained the least fat and those who had the least change in Neat gained the most fat," said James Levine, an endocrinologist at the Mayo Clinic in Rochester, Minnesota.
The study, reported in the journal Science, showed that some naturally slim people may stay that way because they are able to burn off extra calories by general sedentary activity, said Michael Jensen, a member of the Mayo team.
"When some people overeat, Neat switches on to waste the excess energy. This study suggests that efforts to activate Neat, perhaps through behavioural cues, may help to prevent obesity," Dr Jensen said.
The scientists concluded: "As humans overeat, those with effective activation of Neat can dissipate the excess energy so that it is not available for storage as fat, whereas those with lesser degrees of Neat activation will likely have greater fat gain and be predisposed to develop obesity."