Whether it’s quitting smoking or forsaking whoring, eschewing snuff or joining the gym, more resolutions have probably been made—and broken—in pursuit of health than any other cause. When the Georgian rake James Boswell arrived in London in 1762 he firmly resolved to “have nothing to do with whores,” to avoid a repeat of “the loathsome distemper” after first contracting gonorrhoea in his teens. But willpower was not his strong point. After a grand tour of casual sex throughout Europe he had 18 more visits from his old friend “Signor Gonorrhoea” before he died at 54 from the complications of venereal disease. More successful was the 16th century …