Agreeing with he posts about metabolism above. Our guidelines would help some people - but not people with other stuff going on.
Post-op, my diet is not that different from pre-op. I've been vegetarian since I was about 8, I have been logging food and exercise daily in MFP for 7 years and keeping to a calorie deficit, I drink the same amount that I did before (124 oz or more a day). My calories are a little lower right now as I was going on 1300 or less a day for the years before surgery, but not much difference. When I went home for the summer, my old friends didn't notice much of a difference in the amounts I eat now and the amounts I used to eat.
But I have PCOS and my hormones were beyond messed up - I really believe that surgery was the only thing that was going to work for me. Even with that, it's taking ages for the weight to come off - I was told to expect extremely slow loss, but it was still a bit of a shock how slow compared to others. So now I try not to compare, LOL.