After having Gastric Bypass weight loss surgery the weight loss during the first 2 months after having the Gastric Bypass procedure is pretty rapid and you should be losing around as much as 5 and even 15 lbs of weight per week.
Then after the first two months the weight loss is a bit less as in 2 to 3 lbs of weight per week.
After having the weight loss surgery you need to stick to the weight loss diet to keep losing the weight and to keep it off.
If you don't change your eating habits and change to a more healthy diet and not get enough exercise then you might gain the weight back within a year of having the gastric bypass weight loss surgery.