Hmm, this is a complicated and good question.
I have been low carbing off and on for like 15 years. I eat Keto now. It is kind of second nature to me. Most WLS don't eat keto, so this isn't really a WLS patient diet. Since I ate like this before, it doesn't feel like a diet and it doesn't feel related to WLS it just feels like I am finally successful at it. It is easy for me and doesn't feel like a diet, it is just a way of life.
I took Vitamins before surgery and I take the same vitamins I took before just with the addition of B-12. So that doesn't seem different to me.
I think at one year I felt pretty normal. I say one year because I had enough capacity and the ability to eat wide enough variety of things that I can eat out with people and eat normally. I can eat a normal dinner salad because salad greens are a slider basically for me, so I can eat a whole salad and the sorry little 2 to 3 ounces of meat they give you, no issue. I can eat a normal fish portion. I can do decent damage to a 6 oz steak etc. I can chug Water, not at pre-op levels but I can drink 16 ounces of water in about 3 minutes if I am standing. Before surgery I could drink 16 ounces of water without taking a breath.
I really didn't want to feel like I was on a diet or a weirdo for the rest of my life and I don't feel like that. Most of my friends low carb, keto, or paleo. It is pretty common so my friends understand that I don't eat xyz because they don't either. Even if they aren't currently, they have in the past. Having a wide variety of college educated urban friends, almost everyone is doing some kind of special eating, no one cares.
I think it is important to feel normal, because it helps with acceptance. If I felt like I was on a diet and had to watch everything I ate all the time, I would probably relapse. That doesn't mean I eat junk food or fast food. My attitude towards food and what I eat is completely different. My guilty pleasures are grilled nuggets from ChickFilA or an Oh Yeah One bar. Those are my off plan eats. I try to just eat clean food I cook at home, so anything processed or out is an off plan meal to me, even if it still probably eating cleaner than most people. This is normal to me.