Franny Jongbloed

181 7 FEASIBILITY AND SAFETY OF A PREOPERATIVE DIET increase compliance. Interestingly, the morbidly obese patients more often complained about gastrointestinal symptoms during the restricted diet than the kidney donors did. A possible explanation is provided by the link between obesity and functional gastrointestinal disorders (FGIDS), such as irritable bowel syndrome and diarrhea 22 . FGIDS could make obese people more vulnerable to gastrointestinal symptoms when nutritional intake changes. During the DER-diet, both serum albumin and free saturated fatty acids increased. Together with the complaints related to gastrointestinal tract and nutritional intake, these results indicate that the patients on the DER-diet received relatively more fat than during normal food consumption. This could be the cause of nausea and stool change reported by the DER-diet groups. Based on the incidence and severity of the discomfort, together with the percentage of withdrawals from the DER-diet group and metabolic changes, we do not consider the DER-diet an appropriate control diet for future studies. Ideally, determination of adherence to the diet would be based on objective measures. It has been shown that higher intake of calories and protein significantly increases PAB and RBP in patients at risk for malnutrition 23-25 . Both PAB and RBP significantly decreased in patients receiving the restricted diet in this study, while no changes were seen in the DER- diet group, in the control group, or in individuals who did not complete the diet. With only small interpatient variability, both markers therefore have great value in terms of objectively measuring compliance to a restricted diet. In addition, serum levels of BCAAs valine and leucine as well as the combination of all three BCAAs decreased in the restricted diet, with no changes in the DER-diet and the control group. This decrease with lowered protein intake is in line with a recent study by Solon-Biet et al. who showed that higher levels of circulating BCAAs were correlated with the percentage of protein intake 17 . Patients who received the restricted diet also showed a significant decrease in serumurea. Previous studies have shown a relationship between dietary protein intake and serum urea 26 . Interestingly, one patient provided the restricted diet showed no decrease in four of these five markers, raising doubts regarding diet compliance by this individual. Hence, a combination of these markers may very well distinguish between compliance and non-compliance to a diet comprising DR and PR. Further research is needed to validate these markers in larger cohorts of different patient populations in order to establish their independent value as compliance markers. This pilot study has some limitations, including a high percentage of dropouts, a small sample size, and the exclusion of some blood samples that were obtained from non-fasted patients. The high number of dropouts was mostly due to logistical reasons; in some cases, the surgery date was moved up, and in others the patients did not undergo surgery. Some of the included patients declined to participate after providing written informed consent due to the stressful period prior to surgery; these patients were subsequently excluded. These logistical problems are difficult to solve, and further studies should anticipate a relatively