This is an extensive review of many papers from 10 years ago, most data agrees that vegetarian diet is considerably healthier.
More modern literature merely adds that if you go full vegan you need to eat quite some if you want to preserve lean mass.
Obviously, physically active vegetarians who carefully consider their diet (and eat specifically balanced non-ultraprocessed food) compares well to 100% fast food eating couch potatoes. Also obviously, it's far easier to have a nutritional deficit with vegetarian food.
I have yet to see a study where vegetarianism is just imposed with no other guidance. If you have one, I would love to see it.
There's plenty of Harvard studies too.
There's an abundance of literature that meat causes cancer, cardiovascular diseases, etc, but people aren't different to 50s smokers.
Seriously. It's so obvious that cattle farming is among the most earth destroying activities but people prefer not to see, because it impacts their life. Easier to she'll 50k on a Tesla to feel good.
Also, just to point out, I'm not a vegan, all I'm saying is that meat should be heavily limited, which is what I do myself.
[1] https://med.stanford.edu/news/all-news/2023/11/twin-diet-veg...
Or copy-paste vegetarian culinary traditions. They have worked out most of the dietary kinks.
Most people who are vegan are more likely to be health conscious