Also, by plant-based do you mean that the diet can include meat-based sources of nutrition as long as that’s not the main source?
I am not saying that plant heavy diets are bad. On the contrary, I live with one but I still eat meat eggs and dairy and would expect ancient Romans with spending money such as Gladiators to do the same.
Edit. Oh yes, tell me exactly how it works by downvoating me and not providing a source. I forgot that I was not in a place of learning.