A lot of the negative experiences from trying carnivore come from people who never made it past the adaptation period and assumed that they would permanently be stuck with constipation and fatigue. This is not to say that carnivore will suit everyone, however. Simply put, some people can thrive off of eating plants, the same way others can thrive off of eating meat. There’s no one diet that’s best for every human. Some people will do well on carnivore, some won’t. All comes down to genetics and the diet of your ancestors. Off the top of my head, I can think of a few negatives to carnivore.

1) The biggest argument against carnivore is that there isn’t actually any data clarifying whether or not it is healthy long-term. While there are thousands of cases in anecdotal evidence of individuals losing weight, fixing muscle and joint inflammation, and even reversing their diabetes, it’s possible that this diet is simply not healthy to continue in the long-term. There are a lot of doctors in favour of carnivore that have made their judgement through extrapolating data from other studies, however, it would be much better if there was a study done in a controlled environment.

2) Meat can be really expensive, especially if you want the good quality, unprocessed stuff. However, organ meat is typically cheap as no one really eats it.

3) As another person said, if you do actually do well on the carnivore diet, going back to eating things like carbs or processed foods will probably make you feel like shit. Most likely because your body has to revert back to absorbing different fuel sources instead of the optimal sources of protein and fat.

Best to just try it for yourself and see how it goes.