Wow, dude. Citation needed.
Your 'citation' is anecdotal, so here's a couple of my own.
I have a friend in Whistler who is 73 that kicks my ass skiing all day long as we hunt for powder on out of the way double blacks from lift open to lift close, then he pins it nonstop from peak to village. Then he goes to the gym and works out while I chill and have some beers. Then we have a big meaty meal with lots of wine, and then go out on the town til the bars close. He's never been a vegetarian and I've never seen him sober after 9pm. Fkn legend.
As a former vegan who used to go to dinners with the veg society to meet other like minded (fkn crazy) people, I met a lot of them. The only ones who were vegan were ones who only just started, and many of the rest were vegan at some point and told us it would probably not last long and they were right. And then once I ceased that lifestyle I've continued meeting people who used to be vegetarian over the 10 years hence. This is many multiples of times more people than I meet who are actually still vegan or vegetarian. Doesn't count as a citation I know, but living the lifestyle for as long as I did has given me insight that tourists are unlikely to have. Including the insight that says many people who claim to be vegetarian are full of shit. Oh yeah, I occasionally eat fish. And sometimes chicken. But not for a while. Like a month or something. It does show that for many people only occasionally eating meat can be plenty for staying healthy. Totally depends on your body and your output levels. It takes an accommodating body type and rather slow metabolism to maintain that for a lifetime when you're living an athletic lifestyle. It certainly can be done as a vegetarian, but it's extremely rare as a vegan.
How about that 30 bananas a day guy? Looks like his eyes are sucking into his skull and turning black in his later videos. My best guess looking at him is that he's not far off from either living a sub-optimal life or capitulating.