Jamie Oliver gives one of the better TED talks I've seen, on the subject of food and obesity. Please don't be put off that he's pretty overtly plugging his TV show -- I think that is kind of the point. I would recommend his show too, by the way... aspects of it certainly have a made-for-TV feel, but it's hard to listen to him talk and have any doubt about his convictions. I've had three people independently talk to me about this in the last week or so, which makes me the slightest bit optimistic that it might actually catch on.
While I'm on the subject, I think I am pretty late to the party here, but I also watched No Impact Man last weekend at my friend Dave's recommendation and loved it. The trailer alone made me cry a little (also it's on watch instantly on Netflix)