Strolling to the bus stop, fidgeting during a meeting, standing up to stretch, jumping off the couch to change channels, and engaging in other minor physical activities can make the difference between being lean and obese, researchers reported yesterday.
The most detailed study ever conducted of mundane bodily movements found that obese people tend to be much less fidgety than lean people and spend at least two hours more each day just sitting still. The extra motion by lean people is enough to burn about 350 extra calories a day, which could add up to 10 to 30 pounds a year, the researchers found.
James A. Levine of the Mayo Clinic, left, led the study on everyday activity and obesity. At right is Minnesota Gov. Tim Pawlenty.
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"There are these absolutely staggering differences between people who are lean and people who are obese," said James A. Levine of the Mayo Clinic, who led the research published in today's issue of the journal Science. "The amount of this low-grade activity is so substantial that it could, in and of itself, account for obesity quite easily."
Perhaps more importantly, Levine and his colleagues also discovered that people appear to be born with a propensity to be either fidgety or listless, indicating that it would take special measures to convert the naturally sedentary into the restless -- especially in a society geared toward a couch-potato existence.
"Some may say this is a story of doom and gloom -- that people with obesity have no choice. It's all over. I would argue exactly the opposite," Levine said. "There's a massive beacon of hope here. But it's going to take a massive, top-down approach to change the environment in which we live to get us up and be lean again."
Other researchers agreed, saying the new study, while small, provides powerful new evidence that a major cause of the obesity epidemic is the pattern of desk jobs, car pools, suburban sprawl, and other environmental and lifestyle factors that discourage physical activity. And despite generations of parents' admonitions to the contrary, people should be encouraged to be fidgety.
"Figuring out ways to increase physical activity -- not necessarily getting people jogging every day but just building physical activity into a person's day -- are reasonable strategies that have the promise to combat this epidemic of obesity," said William Dietz of the Centers for Disease Control and Prevention in Atlanta.
The number of Americans who are overweight has risen dramatically in recent years, with more than two-thirds now overweight or obese, raising the prospect of an epidemic of heart disease, diabetes and other weight-related ills. The reason for this is a subject of intense debate, with many experts blaming a combination of too much junk food and too little exercise.
Levine and others have done earlier studies suggesting a dearth of routine activity may be part of the problem, but the new study is the most exhaustive to date.
"We all know people who can't seem to stand still and others who hardly move," said Eric Ravussin of the Pennington Biomedical Research Center in Baton Rouge, La., who wrote a commentary on the study. "This is really the first time this has been assessed in this level of detail."
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 data from the previous day's undergarments, and get meals for the day, so the researchers knew 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 predisposed to moving whereas others are born predisposed to sitting.
"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.