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Darwin’s revenge

Darwin Revenge

Why are we getting fat?

     particularly Asians, eating food rich in
  saturated fats will generally increase the
  level of “bad” cholesterol and decrease
  the “good” cholesterol. “When Asians
  move from their traditional environment
  to the West” - or when they start eating
  at their local McDonald’s in Tokyo or
  Beijing - “they immediately get into
  trouble with obesity and heart disease -
  more than Caucasians,” says Jose
 By Fred Guterl with Anne Underwood Ordovas, director of the Nutrition and
  Genomics Laboratory at Tufts
1    Of nature’s many weather University. By the same token, Northern
 conditions, winter at the Arctic Circle Europeans and Celts, and some
 would have to be one of the harshest. Mediterranean populations, tend to have
 It’s hard to imagine that humans would the same cholesterol levels no matter
 have survived generations of frigid what they eat - the work of a gene
 climate without some adaptation giving inherited from Viking ancestors.
 them a way to cope. Scientists have in5    A person’s vulnerability to the
 fact put forward a theory about a “thrifty diseases associated with obesity
 genotype” that some humans acquired depends not just on diet but on his level
 30,000 or so years ago during their of activity as well. And there’s some
 migration from Asia, across a land evidence that activity is a product of
 bridge at what’s now the Bering Strait, to biology as well as culture. A paper
 North America. These genes may have published by Dr. James Levine, a
 given cold warriors an ability to store fat nutritionist and endocrinologist at the
 and metabolize it sparingly, a handy trait Mayo Clinic in Rochester, Minnesota,
 for the dark, cold months when food is reports that a genetic predisposition to
2    Now that the land bridge is long obesity may turn on how much a person
 gone, the descendants of these first fidgets. People who fidget turned out to
 North Americans are stuck with genes expend 350 calories a day more on
 optimized for life in the Ice Age. The average than those who don’t - the
 same traits that allowed their ancestors equivalent of a weight gain of 30 or 40
 to thrive in the Arctic wilderness may be pounds in a year - merely by getting up
 making them uniquely vulnerable to the and moving around more. Studies
 high-fat, high-cholesterol, sedentary suggest a neurochemical basis for the
 American lifestyle. The problem with  natural tendency to fidget. 29 , rats
 evolution is that it can't keep pace with injected with the neuropeptide orexin
 the modern world. began to “run around their cages like
3    Asians are thought to possess many crazy,” says Levine. But scientists are
 of the “thrifty-genome traits”, which may only beginning to get a handle on the
 explain why the number of obese problem. There’s a possibility that fat in
 Chinese doubled between 1992 and the body slows down the metabolism
 2002 to 60 million, according to China’s over the long term. What’s certain is that
 Health Ministry. Some Mediterraneans thrifty genes work in more complex ways
 and Africans may not have acquired the than scientists appreciate at present.
 thrifty genes of Arctic peoples, but their “There’s a profound interplay going on
 hunting-and-gathering ancestors didn’t between the amount of energy people
 leave them a whole lot better equipped. take in and their level of activity,” he
 Half of Brazil is now overweight, and says.
 one in eight is obese. In France and6    The question scientists would
 Italy, about one in three is overweight, ultimately like to answer is how to
 and the proportion is rising. All told, compensate for the obsolete genes
 about 1.2 billion people in the world are we’ve inherited from our primitive
 fat, and another 350 million are obese. ancestors. Identifying the hundreds of
 Obesity-related illnesses, such as heart genes involved - let alone figuring out
 disease and diabetes, are rising.  how to 32 their ill effects - won’t be
4    Scientists are beginning to easy. Undoing thousands of years of
 appreciate the variations in how different evolution never is.
 people respond to diet. For most people, Newsweek