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Mayo Clinic Discovers A Key To 'Low Metabolism' -- And A Major Factor In Obesity

By The Mayo Clinic

Updated February 09, 2005

Updated February 09, 2005
Wiggle, walk, tap your toes, shop, dance, clean your basement, play the guitar to boost your NEAT -- or if you're a scientist, your "non-exercise activity thermogenesis." Mayo Clinic researchers report in today's issue of the journal Science that NEAT -- more powerful than formal exercise -- determines who is lean, and who is obese. Obese persons sit, on average, 150 minutes more each day than their naturally lean counterparts. This means obese people burn 350 fewer calories a day than do lean people.

James Levine, M.D., is the Mayo Clinic endocrinologist who led the study. His research team explored the specific links between inactivity, low energy expenditure and obesity in an effort to devise new treatments for obesity, a public health epidemic.

"Our patients have told us for years that they have low metabolism, and as caregivers, we have never quite understood what that means -- until today," says Dr. Levine. "The answer is they have low NEAT, which means they have a biological need to sit more. A person can expend calories either by going to the gym, or through everyday activities. 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."

He adds that the NEAT defect in obese patients doesn't reflect a lack of motivation. "It most likely reflects a brain chemical difference because our study shows that even when obese people lose weight they remain seated the same number of minutes per day," says Dr. Levine. "They don't stand or walk more. And conversely, when lean people artificially gain weight, they don't sit more. So the NEAT appears to be fixed. But as physicians, we can use this data to help our obese patients overcome low NEAT by guiding the treatment of obesity toward a focus on energy as well as food. We can encourage NEAT-seeking behaviors."

About the Study: Special Underwear

More than 150 personnel were involved in the planning, design, invention, food preparation and data analysis required over the course of about 10 years to produce this comprehensive study of the comparative energetics of lean and obese adults. To detect even the smallest tap of the toe, Mayo Clinic researchers invented a movement monitoring system that incorporates technology used in fighter-jet control panels. They embedded sensors in customized, data-logging undergarments that the researchers designed for both men and women. This allowed monitoring of body postures and movements of 10 obese people and 10 lean people every half second continuously, 24 hours a day for 10 days. The test subjects were healthy recruits who lived and worked in Rochester, and went about their normal routines during the study period. Only two things were forbidden: swimming and eating food the research center did not prepare.

Researchers issued fresh undergarments each morning at the hospital where the test subjects took all their meals. At this time the subjects were weighed, and the data on body position and activity from their underwear movement monitoring sensors was downloaded onto a computer.

"This instrumentation appears slightly bizarre as it gives us a covert window into people's energetics and every activity in a completely unthreatening way," says Dr. Levine. "But because of it, we have a window into people's activity life that no one's ever had before."

Role Reversal: Lean Become Stout; Stout Become Lean

For the next phase of the study, the researchers overfed the lean people by 1,000 calories a day to make them gain weight, and underfed the obese people by 1,000 calories a day to replicate an intense diet. Researchers then monitored their movements every half second for 10 days and compared the results. Even after losing weight, the naturally obese group sat more and moved less. And even after gaining weight, the naturally lean group stood, walked and even fidgeted more than the other group. The researchers' conclusion: Obese people are NEAT-deficient, perhaps as a result of a neurological defect in processing biological drives and environmental cues.

Implications

The Mayo Clinic researchers believe the discovery of the effects of NEAT on obesity is so strong that it should be used to prompt a "NEAT revolution" to reverse the epidemic trends of obesity. "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. Unlike running a marathon, NEAT is within the reach of everyone," Dr. Levine says.

So promising is the role of NEAT in explaining obesity that Dr. Levine believes further studies are warranted to help expand scientists' understanding of the biology of obesity.

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