Gastric bypass versus gastroplasty. A prospective study of differences in two surgical procedures for morbid obesity

57 morbidly obese patients were randomized and operated upon with gastric bypass (GBY) or gastroplasty (GPL). The patients were followed for three years. GBY had a slightly higher early complication rate but a significantly (p less than 0.001) greater weight loss. GBY lost 42.3 +/- 10.9 kg after one year and 38.4 +/- 12.3 kg after three years compared to 29.9 +/- 10.0 kg one year and 24.7 +/- 13.1 kg three years after GPL. No GBY but 10 GPL patients were reoperated upon due to failure to lose or to maintain lost weight. An endoscopic method was developed for postoperative measurement of stoma diameter. Use of this method showed no significant difference in stoma diameter between GBY and GPL. A correlation between weight loss and stoma diameter was found one year after GPL but not after GBY. Also a correlation between peroperative pouch volume and weight loss was seen after GPL but not after GBY. The two methods differed in emptying rate of a semi-solid test meal from the upper gastric pouch. For both methods the energy intake was highly reduced postoperatively, but significantly more after GBY. For a number of nutrients the intake was below minimum recommended levels. Fat cell weight was reduced postoperatively, most pronounced for the abdominal regions and least for the femoral-gluteal regions. The reduction was also significantly more pronounced after GBY than after GPL. Calculated fat cell number was significantly reduced after both methods. It is concluded that the effect on body weight of GPL and GBY cannot be explained by the same mode of action. In GPL mechanical fractures such as pouch volume and stoma size are of great importance, which is in accordance with earlier theories. In contrast to this, the results of GBY cannot be satisfactorily explained by such mechanical factors and additional mechanisms, probably of neuro-endocrinologic origin, must be sought for.