I'm skeptical of carnivore diets. I have tried similar diets, such as a meat-heavy keto diet, and while I agree you see a lot of weight loss quickly (mostly water weight though) I noticed a decrease in energy. For example my longer (1hr+) runs saw my mile times get 1-2 minutes longer without carbs. I looked into it and noticed the people I personally think are the fittest, that is ironman triathletes, all tend to follow the Mediterranean diet. I've come to the conclusion that's the best for me, because I've seen my energy levels increase on that diet, and from studies on life longevity etc believe it is THE best diet without starting to min-max specific things that might help individuals.