I have eaten an almost pure vegan diet for over 25 years. If I am at a dinner where the food is not vegan I will eat the veggies available and not make a big deal about it.
I am turning 56 soon. I weigh exactly what I weighed my freshman year of college. I can still chest press my own weight for 15 reps (I trashed my shoulders in college and don’t try to press more than my 10 rep max anymore), I can bike for hours (Average about 20+ mph, but don’t like being in the saddle for more than one hour, long story involving concrete pool deck and land in on my ass from about 12 feet up as a kid. I was pretty rough on my body until I was about 40.), I regularly swim for over an hour (open ocean hard swim), etc. My blood work is always excellent. I train a few college/college bound athletes every year and love to work out right along side of them as well as being the resistance to many of their resisted exercises.
Before I went vegan I never realized how much my food choices affected things like energy level and overall healthy feeling. I used to eat a lot of beef and fish (I do miss the fresh Ahi/tuna, but with all the news on fish contamination I would probably not be eating it a lot anyway). I started to notice a lot of my friends getting fat and slow. So I decided to make a change before it was too late. Now I don’t even like to smell meat cooking. I wouldn’t think of going back unless I was about to starve to death. Over the years I have learned how to make a lot of the types of food flavors that I used to eat, just without the dead carcass.