[Lopiolis]

Well, more than diet, anything that isn't technical in nature. Economics, (geo-)politics, biology (particularly humans), etc. There's a lot of that fallacy around here that being knowledgeable/smart in one area means that obviously it transfers to every other field.

[npsimons]

I just remember a while back fecal transplants came up here (and other forums I frequent) as a "treatment" for obesity, as they found different gut flora between obese and healthy weight populations. So many people were thinking they could get a fecal transplant to cure their obesity, not stopping to ask maybe what was causing gut flora to be different between obese and healthy weight populations.

And as for diet, the studies are out there. I'm no expert, but I listen to people who could credibly be argued are (as one example Dr. Greger who reads tons of studies and cites them in his videos), and typically their advice comes down to common wisdom that people just don't want to hear: eat food, not too much, mostly plants.