Gastric bypass patients don't stop eating. They are simply impeded from unlimited gluttony by limiting the size of the stomach. If they continue stuffing food, the stomach will stretch to accommodate the intake. Most candidates for that surgery are so enormous that any reduction in food intake will result in weight loss as the metabolic processes try to keep the large body mass alive. The dynamics change when the body reaches a state of "overweight" instead of "morbidly obese".
I don't believe that you have to eat to lose.
Feel free to ignore the research. Your belief is founded on your level of knowledge. I'm simply reflecting the results from MDs and PhDs in nutrition and human physiology. Read some of Schwarzbein's books or Barry Sears. You'll get a better grasp of the mechanics of metabolic physiology.