Petey,
That is a question you should really ask your surgeon. Each person is different, depending on their age, sex, initial weight, medical history, etc. For me, I started at 223 and my ideal weight (not necessarily my goal) is 140 which would bring my BMI to below 25 and in the normal weight range. Therefore, for me, 70 lbs is 31% of my original body weight, and 82% of my excess body weight. It might not be the same for you, or anyone else.
My doctor tells me that on average, LGB patients loose between 40 and 50% of their excess weight, less than the by-pass or sleeve patients, and the weight loss is slower. As you can see, I have done much better than average, but I believe the hard part is just beginning -- to maintain that loss over the long haul. As I said, everyone is different, and I wouldn't compare yourself to someone else.
I also highly recommend that you try and get a handle on why you overeat. As you will see from real life, and reading these forums, it isn't difficult to overeat with the band with some foods. For instance, I could probably eat a gallon of ice cream and my band wouldn't stop me. Or drink milkshakes, eat rich puddings, etc. For me, I have been working with a psychologist at my Bariatric Center to deal with my "food issues", and I really think this has been a big part of my success to date, and hopefully will help me in the long run. I'm not perfect with my eating, or anything else for that matter, but I'm miles ahead of where I was before surgery. I also know that eventually, my stomach will get used to the band and the appetite suppression it provides will not be as strong as before.
The way I look at it is that the band provides the "training wheels" while I learned to eat in a more healthy, resonable and responsible way. However at some point those wheels will come off, and I had better have learned how to eat and nourish myself for the rest of my life. I do not want to have to do this again!!!!!!!!
My 2 cents!
Lisa on a rainy post-labor day in NYC