I think you'll find plenty of people -- nutritionists, doctors, scientists -- who will argue that you're wrong about what humans are designed to eat. But, yes, as you said, if you choose a plant-based diet then you should make sure you're getting enough of certain vitamins and other nutrients. No matter what diet you choose, however, you should make sure it's balanced and healthy and you're getting all your nutrients. I'm sure if I wanted to, I could find studies that show that those who follow a keto diet are lacking and how it's not healthy. There's always a study to prove a point. Anyway, obviously supplementing with Vitamin B12 is important in a vegan diet, but if you do your research you'll find out that Vitamin B12 deficiency is common even in those who eat meat. Many many people choose to go vegetarian, vegan, plant-based for environmental, moral and/or ethical reasons not just diet. If you watch any of the documentaries out there about the CAFO farms, or how they treat and kill the animals, it becomes difficult to want to eat meat. And last, as the current coronavirus has proven, new virus strains are jumping from animal to human more often than ever before, and although this one presumably happened in China at a live meat market, viruses have also been known to jump from animal to human here in the United States at those very crowded CAFO farms. The virulent 2009 swine flu epidemic was traced back to US factory hog farms (hence swine flu). I won't eat meat (or dairy or fish) for all those reasons -- environmental, ethical, humane, health. I'm not going to tell anyone not to eat meat, or argue you're wrong for doing so, but I would recommend that anyone who continues to eat meat boycott meat from CAFO farms and buy only legitimate grass-fed, pasture raised meat.
Since this is a can't lose weight after losing your gallbladder forum, my opinion, which probably isn't worth much, but hey..., is to find a diet that makes you feel healthy and make sure you're getting all your vitamins and minerals and that it's balanced, no processed or junk foods, and that you're getting enough sleep and exercise. Practice the Japanese art of eating only until you feel sated, before you feel full or over-stuffed. I'm not sure there's a one-size fits all diet answer to the problem. I wish there was, or that enzymes were the answer for everyone who has lost a gallbladder. I had been lifting weights and maintaining my weight, although getting very little daily steps in, but now in this lockdown I lost my interest in exercising and I'm fighting the urge to overeat out of boredom and stress. I'm in NY and it's a bit crazy here. I guess maybe I ought to get back to some kind of exercise program, though.
