I think this one has to do with "late dumping syndrome"-- basically, starchy foods cause hyperglycemia --> release of insulin --> catecholamine surge --> diarrhea, etc.
Thought this would be something regarding "bariatric surgery," but nope, just "no starchy foods, because you're pre-diabetic."
I had put "starches" b/c pts that undergo bariatric surgery are only supposed to eat complex carbs (fruits/vegetables) and avoid simple carbs (i.e. breakfast cereal/baked goods)
I think it has to do with the surgery. Getting a gastric bypass or bariatric surgery means you no longer allowing contents to pass through the duodenum. So that would mean if you had a starchy meal you would not be able to release the appropriate enzymes from the pancreas to allow for digestion.
Please correct me if I'm wrong!