4 min read JESSE EISENBERG HAS never seemed like the type to hold back on what he’s really thinking. The 42-year-old actor, writer, and director is still probably best known for his quick-tongued turn as Mark Zuckerberg in David Fincher ’s The Social Network, but if he’s got any signature across his work in front or behind the camera, it’s a penchant for both his characters and his camera to feel totally, completely honest to what he’s experiencing at any given moment. That signature couldn’t have seemed more true on Tuesday at Men’s Health ’s offices in Midtown Manhattan, when Eisenberg was interviewed by Men’s and Women’s Health Editorial Director Richard Dorment for the second annual Men’s Health Lab event. Eisenberg was on stage discussing his experience donating one of his kidneys to a stranger last year , and, eventually, the conversation arrived at the subject of health trends in the pursuit of longevity . These are the kinds of trends that it seems like everyone is getting into right now.…