Some Couch Potatoes Born That Way, Fat Study Says
for National Geographic News
|January 27, 2005|
Are sedentary obese people intentionally lazy? Not according to a new study, which says some people are natural-born couch potatoes. The study also finds that people who are overweight can take some easy steps to shed pounds.
Researchers at the Mayo Clinic College of Medicine in Rochester, Minnesota, found that obese people with sedentary lifestyles appear to have a genetic inclination to sit around a lot.
The study, to be published tomorrow in the journal Science, investigated the link between inactivity, low energy expenditure, and obesity. The research was part of a program to devise new treatments for obesity, which is fast becoming an epidemic in the United States and other Western nations.
Researchers say there is a factor more important than strenuous exercise in determining who is fat and who is lean. They call it non-exercise activity thermogenesis, or NEAT. The term refers to the calories people burn during everyday activities such as walking, fidgeting, or even just standing.
The study's lead author, James Levine, a Mayo Clinic endocrinologist, said, "Our patients have told us for years that they have low metabolisms. We have never quite understood what that means. The answer is they have low NEAT."
While most people think they must perform physical exercise, such as gym workouts, to burn off excess calories and lose weight, Levine says this isn't the case.
"Our study shows that the calories that people burn in their everyday activitiestheir NEATare far more important in obesity than we previously imagined," he said.
Levine adds that couch potatoes aren't necessarily intentionally lazy. Low NEAT, he says, most likely reflects genetic differences, because his study showed that even after obese people lose weight, they are still inclined to sit for the same amount of time.
Citing the lower obesity rates of 50 years ago, Levine says environmental factors are also at work.
"What has changed in 50 years?" he said. "Not our biology but our environment. This promotes sedentary behaviors."
The study tracked the posture and body position of 20 sedentary volunteers for ten days. This was done via a special undergarment that incorporated technology used in fighter jet control panels. Embedded sensors allowed researchers to monitor even the smallest movements of volunteers every half second, 24 hours a day.
While all subjects were self-proclaimed couch potatoes, ten were lean and ten were mildly obese. On average, the lean individuals stood and moved about for two hours longer than those who were obese.
The same results were found over a second ten-day periodafter the lean group was overfed by a thousand calories a day to make them put on weight. Also before the second round, the obese volunteers had been put on a crash diet and lost weight.
The study team concluded that the obese people in the study are predisposed toward sedentary behavior, perhaps as a result of a neurological defect caused by brain chemical imbalances.
The researchers say rodent studies support this idea. For example, physical activity increased in rats when injected with orexin, a brain chemical associated with sexual arousal.
The researchers say that if the obese volunteers had adopted the NEAT-enhanced behavior of their lean counterparts, they could burn an extra 350 calories a day. Over a year, that would mean weight loss of around 33 pounds (15 kilograms)without undertaking any strenuous physical activity.
Levine says our calorie expenditure increases 10 percent if we stand up instead of sit down. He adds that even walking at 1 mile an hour (1.6 kilometers an hour) increases calorie use 100 percent.
The researchers believe the discovery of the strong effects of NEAT on obesity could make a big difference in helping people beat the condition.
"This is entirely doable, because the kind of activity we are talking about does not require special or large spaces, unusual training regimens, or gear," Levine added. "Unlike running a marathon, NEAT is within the reach of everyone."
Levine has a treadmill in his office, which he walks on while using his PC. He also recommends activities such as vacuuming, home repair, and walking the dog. The U.S. Department of Health and Human Services (HHS) is now promoting non-exercise activity, or NEAT, as part of a campaign to address the country's chronic obesity problem.
HHS published a report last year stating that 400,000 deaths in the U.S. in 2000 were related to poor diet and physical inactivity. The toll represents an increase of 33 percent since 1990. Two out of three Americans are currently described as overweight or obese.
Non-exercise activity is being promoted via initiatives such as www.smallstep.gov, a Web site created in partnership with HHS. It includes simple physical and dietary advice to help Americans lose weight.
Tips include: skating to work instead of driving, mowing the lawn with a push mower, sitting up straight at work, taking the wheels off suitcases, and taking the stairs instead of the escalator.
The HHS obesity campaign is designed for a general audience, including disadvantaged communities.
Speaking at the campaign's launch in the spring of 2004, departing HHS Secretary Tommy G. Thompson said, "It provides entertaining and achievable ideas for healthier living, and includes activities that we can all make time for."
Don't Miss a Discovery
Sign up our free newsletter. Every two weeks we'll send you our top news by e-mail (see sample).
|© 1996-2008 National Geographic Society. All rights reserved.|