As different as Venus and Mars: time to distinguish efficacy (can it work?) from effectiveness (does it work?)

Although the news has not yet hit the New England Journal of Medicine, there is an epidemic sweeping North America. You can read more about it on the BJSM blog (http://tiny.cc/00vmq) but it kills as many people in USA as do smoking, diabetes and obesity combined. NIH Nightmare. Yes, this worse-than-Ebola disease -smokadiabesity -kills a frightening 14% of Americans. Fortunately, Professor Steven Blair had a premonition about this epidemic, so he already has 20-year prospective data comparing deaths from the new epidemic and from low fi tness (fi gure 2). 1 Astonishingly, low fi tness still kills more Americans (16-18%) than even rampant 'smokadiabesity'.