Mayo Clinic discovers a key to 'low metabolism' – and major factor in obesity
ROCHESTER, Minn. -- 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 (http://www.sciencemag.org/content/current/ ) 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.
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.
Collaboration and Support
In addition to Dr. Levine, members of the Mayo Clinic research team include: Matthew Clark, Ph.D.; Michael Jensen, M.D.; Paul Kane; Alisa Krizan; Lorraine Lanningham-Foster, Ph.D.; Shelly McCrady and Leslie Olson. The study was supported by grants from the National Institutes of Health; Mr. and Mrs. T.S. Ward; the Minnesota Obesity Center and Mayo Foundation.
10 Neat Things to Know About NEAT:
The most detailed and data-rich study of obesity ever undertaken was performed at the Mayo Clinic and published January 27, 2005 in the journal Science. Results show that it's metabolically more effective to put more NEAT -- "non-exercise activity thermogenesis" -- into your life to achieve a healthy body weight, than to seek organized exercise.
To prepare, design and carry out this NEAT study over the past decade, Mayo Clinic brought together:
- 20 study participants who were willing to forgo Christmas peanut brittle, Halloween Milky Ways and all restaurant and home meals. Every meal had to be taken at the hospital, without exception.
- A biomedical team at Mayo Clinic of approximately 150 people, ranging from endocrinologists, dieticians to specialists to conduct analyses with a mass spectrometer.
- The periodic $1,000/person glass of water. This was a special metabolic test that required drinking treated water with tracers to monitor the person's metabolism as a way of providing researchers a measure of compliance that test subjects were eating only meals prepared for them by hospital staff.
- A dedicated kitchen staff to cook 20,000 meals over the test period, starting at 5 a.m. each day --without skipping a beat, food group or strange hankering.
- 150 million lines of data was downloaded from the data-loggers and analyzed.
- Committed study participants to clean their plates -- and scrape them, too, with a rubber scraper -- so every calibrated calorie that was served was also consumed.
- Custom-made, data-logging undergarments that all participants wore 24 hours a day, exchanging a new pair every morning at the hospital at breakfast. The bottoms look like bicycle shorts and the women's tops look like sports bras. The men's tops look like undershirts.
- Jet fighter control panel motion sensing technology embedded in the special underwear to monitor every tilt and wiggle of the participants.
- No swimming -- due to the potential water damage to the motion sensors.
- No particular activity regime was endorsed or prescribed. Participants were told to go about their normal work, recreation, rest and romance routines.
Says James Levine, M.D., the Mayo Clinic endocrinologist who led the study: "This was a massive team effort. It should be said that this collection of teams at this level of expertise don't appear anywhere else in the world."
Source: Eurekalert & othersLast reviewed: By John M. Grohol, Psy.D. on 21 Feb 2009
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