Concerning the guy in the article eating "meat" for one week with undesired effects, I glanced through and saw he was eating a lot of "meat" sticks. What? Of course he had digestive issues. Did he look at the ingredients in those things? I just completed my 80 day animal foods diet, and I can say I stayed far away from those things. They contain a lot of nasty stuff that isn't animal. Plus sounds like the author combined starting low carb at the same time. Keto flu on top of everything. Better in my opinion to be completely fat adapted first, then try all animal foods. Currently now adding back a little stuff like coconut to see what happens, as I was fine with beef but would like maybe a little wider variety of fats if well tolerated. And I didn't go interviewing any registered dietitians, as they're usually trained to automatically assume meat and saturated fat are bad despite good scientific studies that say otherwise, so of course the RD was negative about it.

Edit: Martin, your comment popped up while I was still typing mine. Looks like you already spotted those problems.