Energy and nitrogen absorption after biliopancreatic diversion

Background: The strict long-term weight maintenance in good nutritional con ditions observed after biliopancreatic diversion (BPD) needs to be explaine d. Materials and Methods: 15 operated subjects were maintained at an isoenerge tic and isonitrogenic diet as similar as possible to their usual diet. Appa rent absorption (AA) of energy, fat, nitrogen and calcium was calculated su btracting the fecal content, measured directly, from the oral intake, deriv ed from tables. The alimentary protein absorption was directly determined b y I-125 albumin oral administration. Results: Mean AA for energy and fat was 57% and 32%, respectively; AAs were unrelated as absolute value and negatively associated as percent of the in take with the energy and fat intake. I-125 intestinal absorption was 73%, w hile nitrogen percent AA was 57%, indicating higher than normal loss of end ogenous nitrogen. Calcium AA was 551 mEq/day, 26% of the intake. A positive correlation between nitrogen and calcium AA as absolute values and aliment ary intake was observed, while there was no correlation when AA were consid ered as per cent of the intake. Conclusions: For energy and fat, an increase in intake corresponds to an in crease in percent malabsorption, so that the absolute amount absorbed tends to remain constant, accounting for the excellent weight maintenance observ ed following BPD. This was confirmed by a long-term hypernutrition study af ter BPD. On the contrary, for nitrogen and calcium, the percent absorption tends to remain constant when intake varies, so that an increase in aliment ary intake results in an increased absolute amount absorbed.