Background One of the main effectors on the quality of life of living-kidney donors is postoperative fatigue. Caloric restriction (CR) and short-term fasting (STF) are associated with improved fitness and increased resistance to acute stress. CR/STF increases the expression of cytoprotective genes, increases immunomodulation via increased anti-inflammatory cytokine production, and decreases the expression of pro-inflammatory markers. As such, nutritional preconditioning by CR or STF represents a non-invasive and cost-effective method that could mitigate the effects of acute surgery-induced stress and postoperative fatigue. To investigate whether preoperative STF contributes to a reduction in fatigue after living-kidney donation, a randomized clinical trial is indicated. Methods We aim to determine whether 2.5 days of fasting reduces postoperative fatigue score in subjects undergoing living-kidney donation. In this randomized study, the intervention group will follow a preoperative fasting regime for 2.5 days with a low-dose laxative, while the control group will receive standard care. The main study endpoint is postoperative fatigue, 4 weeks after living-kidney donation. Secondary endpoints include the effect of preoperative fasting on postoperative hospital admission time, the feasibility of STF, and the postoperative recovery of donor and recipient kidney function. This study will provide us with knowledge of the feasibility of STF and confirm its effect on postoperative recovery. Discussion Our study will provide clinically relevant information on the merits of caloric restriction for living-kidney donors and recipients. We expect to reduce the postoperative fatigue in living-kidney donors and improve the postoperative recovery of living-kidney recipients. It will provide evidence on the clinical merits and potential caveats of preoperative dietary interventions. Trial registration Netherlands Trial Register NL9262. EudraCT 2020-005445-16. MEC Erasmus MC MEC-2020-0778. CCMO NL74623.078.21

IntroductionHepatocellular adenoma (HCA) is an uncommon, solid and benign liver lesion, mainly occurring in women using oral contraceptives. Patients are advised to stop using oral contraceptives (OC) and, as overweight is frequently observed, dietary restrictions. Metabolic changes are assumed to play a role and it has been suggested that diet may help to reduce tumour size. A low-calorie ketogenic diet (LCKD) has been shown to induce weight loss and multiple metabolic changes, including the reduction of portal insulin concentrations, which downregulates hepatic growth hormone receptors. Weight reduction and an LCKD can potentially reduce the size of HCAs.Methods and analysisWe designed a matched, interventional cohort study to determine the effect of an LCKD on the regression of HCA. The study population consists of female subjects with an HCA, 18–50 years of age, body mass index>25 kg/m2, who are entering a surveillance period including cessation of OC. A historical control group will be matched. The intervention consists of an LCKD (approximately 35 g carbohydrate/1500 kcal/day) for 3 months, followed by a less strict LCKD for 3 months (approximately 60 g carbohydrate/1500 kcal/day). Main study endpoint is the diameter of the HCA after 6 months, as compared with the historic control group. Secondary endpoints include adherence, quality of life, change in physical activity, liver fat content, body weight, body composition and resting energy expenditure.Ethics and disseminationThe medical ethical committee has approved the study protocol, patient information files and consent procedure and other study-related documents and procedures.Trial registration numberNL75014.078.20; Pre-results. https://www.trialregister.nl/trial/9092