Vegetarians historically did it for ethical reasons. Pythagoras because he believed animals have souls, Plato too, Benedictine monks ate fish because fish don't care for their young so the parents won't be upset if you eat their children (!), etc, etc.  Even Alex Gleason does it for ethical reasons.

YET epidemiological studies show vegetarians living a very long time, and it's pretty obvious when you know a lot of them (I grew up a Seventh Day Adventist, many of my ancestors lived to about 100), and track health gurus and see the vegetarians living past 100 but the meat heavy promoters dying in their 60s.  I've got a huge list of people, it's super obvious, but people just refuse to accept it because IMHO they like to eat meat, so their active brains construct reasons and logic to defend this position... which is the common backwards way most people think.

I'm not saying a little meat is bad.  It isn't.  Pure vegetarianism has problems with iron, B-12, protein quality, and probably other things.  That's why I'm not a vegetarian.

And while I agree with Pythagoras that animals have souls (that is to say, they are conscious aware beings)... they don't after they are dead.  After they are dead, they are meat, which is good as a food. 

 there is something called "healthy user bias" that confounds these epidemiological studies.

namely in a society in which it is believed that meat is unhealthy and vegetables are healthy those who are health conscious will eat vegetables and those who are not will eat meat and the result will be that vegetarians will live longer than meat eaters simply because they are more health focused overall.

by contrast if you look at different cultures / nations ( as opposed to different individuals within same nation / culture ) then Koreans eat the most meat ( they eat dogs too ) and live the longest ... 

 as for Ethical Vegans most of them are just afraid of death but pretend to do it for ethical reasons.

per Nietzsche morality is always rationalized after the fact from self interest  

 I think that is likely true. 

 That is a good point.

Also, I'm far more skeptical of the ability to correct for confounders than, say, Walter Willett is.  For example, once they found a confounder and adjusted for it and their results changed massively, and an interviewer asked them about this problem, and they just tried to play it down.  But clearly, getting the confounders correct is essential... and also impossible.

Nonetheless, I'm also not convinced that this is entirely explanatory.

Koreans are small.  It is well known that within a species, the smaller individuals live longer.  (Between species, the larger ones live longer).  So that one is confounded too. 

 well you can do controlled studies but those are expensive to run long-term or with large enough sample size and even in the best designed studies there is the issue of who is paying for them ... 

 culture and family values determine our diet .. we can stay healthy  in a very wide range of food choices ..  I for example can live only on milk  alone  .. 

 

 i create my own culture and values. 

 You are both correct, and there are ways for my mom and I to maintain our dietary perculiarires/sovereignty when with the broader family without influencing or drawing needless attention to how much rice or plantains we put on our plates vs how much meat and legumes are on the plate.