The short answer is that we don't know. Refreshingly enough, this article seems to focus on that fact. There are studies that say eating meat will give you cancer, or just kill you younger in general, but there are studies that show the opposite, and studies that show no correlation. And pretty much all of these studies have issues, the biggest usually being, as the article says, that they're observational, based on…
> Does a low-carb diet improve health outcomes? Or a vegan diet? We just don't know, and anyone that tells you they do know is either selling you something or, at best, telling you what worked for them.
Yup; and the same applies to anyone looking to refute a diet they do not like. For example, a vegan asserting that the carnivore diet is unhealthy and vice versa.