Why Are Some Naturally Skinny? Gene 'Overdose' May Be Responsible

LONDON — People with extra copies of certain genes are much more likely to be very skinny, scientists said Wednesday in the first finding of a genetic cause for extreme thinness.

In a study in the journal Nature, researchers from Britain's Imperial College London and the University of Lausanne in Switzerland found that a duplication of a part of chromosome 16 is associated with being underweight.

Previous research has found that people with a missing copy of these genes are 43 times more likely to be morbidly obese.

"This is the first genetic cause of extreme thinness that has been identified," said Philippe Froguel from Imperial's school of public health, who led the study. "It's also the first example of a deletion and a duplication of one part of the genome having opposite effects."

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