I lost 16lbs in the first month after banding but everyone is different, we all lose at different rates so would be hard to make a definitive sort of response. A lot of people dont lose weight at all till they start feeling restriction from fills. My first month was all liquid diet, followed by 1 month mushies then solids after that. I ate a lot of soups, broth and 0% fat greek yoghurt mixed with skimmed milk made into a drink, i did not do protein shakes
I am still losing a year post op but have slowed down considerably. Average was 2 to 3lbs a week now its maybe 1 or 2 lbs a week at most .. not far to go now but will continue just eating healthy food and exercising to maintain what i have lost. Some people manage to lose just from eating smaller portions of normal type food u will have to learn what works for you ..
good luck