After a Roux-en-Y gastric bypass, several mechanisms contribute to induce weight loss:
– A decrease in the feeling of hunger linked to the decrease of Ghrelin (hormone stimulating appetite) but less than after a sleeve gastrectomy,
– A decrease in gastric capacity,
– A very accelerated gastric emptying associated with the short-circuit of the pylorus causing earlier secretion of satiety hormones (PYY and GLP1),
– A malabsorption that mainly affects fats and to a lesser degree proteins,
– Finally an aversive reaction to sugary foods in the case of dumping syndrome.