I have an acquaintance whose every third Facebook update is about types of food you should or shouldn't eat for whatever reason. She's not into fitness or dietary ethics (vegetarianism, sustainability, etc.), and the only possible reasons I can think of for her to opine over diet so much are (a) it gives her secret superpowers she's not allowed to talk about, or (b) she has a really strong orthogonally-political affiliation based around food.