I think we will see, like most things, that there is no one size fits all approach for every body constitution.

I have one friend who has seen great benefits from a long term, strictly carnivore diet.

I have two friends who have seen major benefits in long term, strictly vegan diets.

Everyone I know who has tried it, has benefited from removing regular alcohol consumption, preservatives and added sugars, opting for a balanced diet of actual food together with regular physical activity.