I wanted to post this as someone who had an open RNYGB in 2005, and while it was successful there are a few things I KNOW get ignored, dismissed, or just refused to believe.
1. I think the most important thing is to seriously take care of your mental health first. No one overeats to the point we needed weight loss surgery because they were happy. I beg you- please don't ignore the reason WHY you eat the way you do.
2. I have learned that even almost 20 years after my surgery, general practitioners just don't get the intricacies off treating someone who's had RNY or DS surgery. I've met ONE, and she's an Oncologist/Hematologist. You have to do the research and figure out where EVERY mineral and vitamin is absorbed in the digestive tract. So when you're terribly anemic (more on this in a moment) and your Dr says "take iron supplements" you'll know that iron is absorbed in the duodenum- which we no longer use. You HAVE to do the work to advocate for your own health.
3. Speaking of anemia.... It would have been nice if I knew that iron deficiency post surg isn't a "potential" malnutrition issue. IT'S A FOR CERTAIN ISSUE. Now I've had to literally argue with f'n doctors to explain how hemoglobin level alone is NOT the sole indicator of anemia. My Hgb was great, BUT... My ferritin, iron, TIBC, and iron sat% were a hair above needing a blood transfusion. You know your body. You know when something's not right, but iron deficiency comes on slowly. It's hard to say if you're tired or cold or weak because of iron deficiency or another reason. But when you're eating a 10# bag of ice every two days and you also feel like a wrung out dishrag, I'd bet my own money your iron panel comes back screwed. Please, please don't go for years feeling like garbage because a doctor tells you you're fine.
4. I know at least 15 people, in my day to day life, who have had either RNY or the sleeve. Every single one of us has severe tooth problems. Reflux, vomiting, plus lack of calcium and vitamin D are a killer for teeth. Just pay attention and don't end up like me needing 25k in dental work.

I just feel really defeated when I'm treated like I don't know what's going on with my own body- but I'm also really stubborn! I'll tell you exactly what I went through, how I kept from gaining it back, struggles I've had that were direct results of surgery, etc.