The gastrectomy operation which is performed at the investigators institute is Billoth I or II operation. The operation virtually eliminate the half of the body and most of the antrum. If fundus is involved also, proximal gastrectomy is the operation of the choice. Most of the patients who have these operations will lose weight during 1-3 months after surgery, thereafter slowly recover. However, the mechanism of the weight recovery has not been elucidated so far.