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Man says gluten-free lifestyle helps him defy age

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Mark Sisson is a former marathoner and Ironman triathlete.  At 59, he looks and says he feels much younger. He credits his health to living a gluten-free lifestyle.  Josh Mankiewicz’s full report on the growing popularity of the gluten-free lifestyle airs Thursday, Oct. 4 at 10pm/9c on NBC’s Rock Center with Brian Williams.