Is a vegan diet healthier than eating meat and dairy?

It's not just calories. A diet of vegan french fries, potato chips, and sugary beverages probably won't help vs. a balanced omnivorous mediterranean diet even if the overall calories are the same.

The gut microbe issue is interesting; vegan seemed to eat less sugar and fewer processed foods yet suffered from lower gut microbe diversity (and "below average" sugar and fat processing in spite of sustained energy and low cholesterol.)