Christ, we know eating red meat is bad for you. We know that a balanced diet favoring vegetables is good for you. Why are seemingly well educated and intelligent people on this awful diet?
What do we know, exactly? Because we've known lots of stuff that turns out to be bunk. And I am seeing increasing evidence that a one-size-fits-all diet isn't healthy - some people will need more or less of different things, or to abstain entirely from categories.
Not saying this is a good idea - but It's hard to say to what degree it isn't.
For some, maybe the cognitive advantage outweighs the potential health risks.