Variable Selection for Assessing Risk Factors for Weight and Body fat Gain During the First Year After Kidney Transplantation.

Body fat and overall weight gain are common after kidney transplantation and are associated with poor clinical outcomes. Therefore, identification of at-risk patients is relevant for preventive interventions. What variables influence weight and fat gain in patients in the first year after kidney transplantation? Prospective and retrospective cohort studies published in or after 2001 naming fat and/or overall weight gain during the first year after kidney transplantation as outcome variable(s) were systematically searched in Medline/Pubmed in November 2018 and March 2022. We identified 16 studies examining a wide variety of potential factors influencing weight and fat gain over the first posttransplant years. These included genetic, socio-demographic, behavioral, biomedical, psychological and environmental factors. For a number of variables, study results were contradictory: some studies indicated preventive impacts on weight or fat gain; others concluded that the same factors increased it. Cases were discussed with 2 clinical experts. We eventually agreed on 13 potentially relevant risk factors for post-transplant weight/fat gain: age, gender, genes, income, ethnicity, education, eating habits, physical activity, smoking cessation, baseline BMI, baseline fat, depression and perceived overall wellbeing. Before integration into clinical practice, a critical evaluation of all potential risk factors' suitability for assessment will be necessary. In addition to feasibility, operational definitions and measurement methods must also be considered. To reduce the list of risk factors to the most relevant, a first testing within a prospectively collected data set is planned.