Fiber. Most all-meat diets suggest taking fiber or psyllium husk supplements for this very reason.

Eating a diet of meat probably does make you feel good. Especially in the morning and at lunch, the fats will keep you full all day so you’ll eat less garbage (e.g. Diet Coke as mentioned in the article). That’s not to say it won’t have some serious repercussions down the line, but I would be it does create a sort of local optimum that may be better than the average American artificial diet.

IMO they're probably just being contrarian.

> we know eating red meat is bad for you. We know that a balanced diet favoring vegetables is good for you

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.

It's well understood that the brain performs differently in ketosis, it's why the diet is used to treat epilepsy.

For some, maybe the cognitive advantage outweighs the potential health risks.