The Difference Between on Message and in Message

So I was talking Monday to John Mackey, the co-founder and co-CEO of Whole Foods Market. We were getting ready to do an interview that will appear in the January-February issue of HBR and on the website Big Think. But the Big Think cameras weren't quite ready yet, so we were just chatting. I asked Mackey about the more-vegan-than-thou diet that he's been following for the past couple of years. One of its distinguishing characteristics is that it bans the consumption of many non-whole — that is to say, processed — foods. Such as olive oil.