Late effects of gastric bypass for obesity.

We studied 41 patients who had gastric bypass for obesity from 1974-1979. The procedure was well received by patients and most achieved adequate weight loss, but most subjects consumed inadequate diets and many developed iron and/or vitamin B12 deficiencies. Ten were anemic and 13 had been treated previously for postbypass anemia. Severely vitamin B12-deficient subjects did not respond to 50 micrograms oral vitamin B12 tablets, but those with milder deficiencies usually did. Schilling tests were usually abnormal and corrected when intrinsic factor was given. Many subjects developed manifestations compatible with osteoporosis due to inadequate calcium intake and absorption, and some also developed abnormal laboratory tests suggesting coexisting osteomalacia. Hematopoietic complications of gastric bypass can usually be prevented and are relatively easy to treat, but musculoskeletal complications may be more difficult to prevent and treat.