[deno]

Sustainability should be whether or not you are going around hungry. Because if not, then why would you ever stop the diet, or even worse go back to the old habits? Why would it be surprising that you would then gain your weight back?

And yeah muscle tissue is the important one. Any diet is sustainable until you burn through all your secondary reserves. How many buff vegetarians do you see? In my experience, you need to be a bona fide nutritional expert to maintain muscle mass on an exclusively plant-based diet.

[esailija]

Chronic reflux, constipation, nocturnal urination etc also make these diets unsustainable.

As buff vegan the proportion of buff vegans among vegans is probably the same as proportion of buff non-vegans among non-vegans. You have to be braindead not to be able to figure out what to eat as vegan to grow muscle, in the worst case I guess you can go to factory farmers who have mastered the art of growing muscle from plants..