re: What are some of your thoughts on the carnivore diet

Fasting does increase metabolism and hgh. I don't exactly know the details of all the mechanisms of such stuff but my understanding is ketones can only be made from a fat source, so your body can't cannibalize muscle into ketones. Your body can metabolize anything into insulin though, which what I mean with muscle breaking down into insulin.

I'm referring to being in a calorie deficit so that there is no confusion.

Carnivore Diet: Why would it work? What about Nutrients and Fiber?

That is imo a great channel for this stuff. He has several videos on carnivore/keto/nutrition and uses scientific/medical studies. It is hard to compare diets using the same measurable across diets because depending on how close you are to things like full ketosis or carnivore diet you don't need as many nutrients because you aren't getting so many antinutrients, etc. The biochemistry matters a lot along with the hormones. As someone else said, fat is super efficient food so allows for more energy to be expended on developing a bigger brain, while fat also controls hormones, etc.