Regaining weight?

For those of you longer post-ops, has anyone gained a significant amount of weight back over time? I am almost 2 years post-op and my surgeon told me the other day that the surgery will stop working for me soon. He asked me what I would do if I begin to gain weight and I told him I would go back to following the rules and exercise more. I am currently underweight and have to be careful of exercising too much. Prior to my hernia repair I did find myself grazing. Now after the repair I am sticking to my meals only. Just wanted to hear other opinions or experiences. Thanks. Char