A few years ago, Harriet Hall googled "The One True Cause of all disease", just to see what the Internet would come up with. She counted 67 One True Causes before she got bored (52 of them made it into the handy chart above).
Besides making for an amusing anecdote, this little exercise also helps illustrate why there's a problem with ideologically driven medical treatments — the sort that comes from people who are pushing a lifestyle or a philosophy along with ostensible healthcare. It's both intriguing and convenient to think that, if we just open the right secret door, we can find the thing that's actually causing all our problems. The truth, unfortunately, seems to be that our bodies and the world they inhabit are complicated and messy and that lots of of things can lead to disease (doctors typically learn to divide these things into nine different categories, Hall says). In fact, a disease we think of as a single entity can have its roots in more than one thing. All of this is pretty obvious but it's the kind of obvious that's worth rubbing our noses in on occasion. If somebody tells you that everything from obesity to bipolar disorder to allergies to cancer all stem from the same root and can be treated or prevented with the exact same treatment, there's probably good reason to question what they're telling you.