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Fat and Happy?

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Fighting the Thrifty Gene 3 pages: | 1 | 2 | 3 |

Photo of Tohono O'odham eating foodIn "The Desert's Perfect Foods," Alan met members of the Tohono O'odham tribe of Arizona. Though the Tohono O'odham, and their nearby relatives the Pima, eat and exercise about the same amount as other Americans, the tribe's obesity rate is more than twice that among Caucasian Americans. Why? It is a question scientists have been trying to answer since 1965. Dr. Eric Ravussin, who has worked with the Pima for more than 15 years, weighs in on the Pima paradox.
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Metabolic Measures

Born and raised in Luzon, Switzerland, Eric Ravussin always wanted to be a scientist. After graduating from the University of Luzon, Ravussin began work on his Ph. D, in human physiology, perhaps inspired by the University's metabolic chamber - an enclosed room that measures metabolic activity. As a post-doctorate at the University of Vermont in Burlington, Ravussin worked on a well-known feeding study of prisoners. After two years, he returned to Switzerland.

Photo of Ravussen
Eric Ravussin studies the genetic components of weight gain  

In 1984, he returned to the states to set up a metabolic chamber for the National Institutes of Health in Phoenix, AZ- not far from the Pima reservation. The chamber would be used to compare the metabolic rates of different ethnic groups, including the Pima. Ravussin had planned to stay for just two years.

"But I guess I stayed for 16," he laughs from his office at the Pennington Biomedical Research Center in Baton Rouge, Louisiana.

In the Pima, their survival mechanisms evolved to store fat extremely efficiently.

During those 16 years, Ravussin's work with the Pima has illuminated the genetic components of obesity. Ravussin estimates some 200 genes work together to control eating behavior and weight regulation, though probably only 5 to 15 play the most important roles. Why such a complex arrangement for something so crucial as feeding?

"Any important behavior needs alternate pathways," says Ravussin. "When it comes to survival mechanisms, you need redundant systems."

Old photo of woman by the lake
The Arizona Pima showed no unusual rates of obesity pre-WWII  

In the Pima, Ravussin's research indicates, their survival mechanisms evolved to store fat extremely efficiently, a genetic make-up that would have served the tribe well in the harsh desert climes of the southwest. Today, however, this so-called "thrifty gene" means roughly 70% of the Arizona Pima are obese.

"There's no question these people suffer from a genetic disease," says Ravussin. "It's not sloth and gluttony."

Type II diabetes, strongly associated with obesity, is also epidemic in the tribe, striking younger and younger children- something almost unheard of in the general population.

"The Pima have a genetic liability. But it's only a liability in our environment," says Ravussin. "It was an asset to survival in mankind's history."

Though Ravussin's research has not yet isolated the genes and metabolic pathways responsible for the Pima's obesity epidemic, he is optimistic the work will one day help all overweight people.

Photo of woman in chamber
  A Pima woman sits in a metabolic chamber

"We've known about the Pima's problem for 30 years, but nothing earthshaking has been done," he says. "But I still hope, when we know the exact genes, we will be able to correct the problem."
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3 pages: | 1 | 2 | 3 |

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