At 3 years out, eating only 800 calories a day will cause your metabolism to be screwed up as it was before surgery.
You do need less sugar and white carbs. You also need more protein and veggies. Exercise doesn't really do much for weight loss, but it allows you to eat a little more without weight gain, and makes you feel better as well.
So don't curtail calories too much or your body will begin to conserve those calories even more in the form of stored fat. Just eat food that you really like that also falls into the category of meat, fish, poultry and vegetables. Throw all sugar and junk out of the house, even if you have a husband and kids, they should support you, and everyone can benefit from more good food.
As long as you pay attention to what you eat, you won't get back to where you were. I think we forget, and just eat like we did before surgery out of letting old habits sneak back in.
For many people with all types of weight loss surgery, I think a few pounds of " rebound" gain happens. For me, at 3 1/2 years out it was first 5 lbs, then 10. I would lose it and then gain it back. At 53, and menopausal, i decided it was not worth driving myself crazy over, so I have come to accept the 10 lbs. I haven't gained any more in the last 2 1/2 years. I am now 6 and 1/2 years out.
If I see myself gaining at all, even one pound, I cut out the bread, rice and potatoes, and in a couple of days it's gone.