It is normally as a result of weight loss surgery but any surgery to the stomach involving the pylorus (the opening between the stomach and the duodenum) and the duodenum (first part of the small bowel) can cause it.
I think most people adjust their diet and over time it will resolve itself. If that doesn't work medication can be prescribed to slow the digestive process down and if that doesn't work, further surgery to restrict the area around the pylorus.
Dusty. xxx