Changes in Body Composition Compartments After Kidney Transplantation: A One-Year Prospective Study.

Background/

Objectives

Weight gain after kidney transplantation is frequent but heterogeneous, often accompanied by changes in body composition that influence long-term outcomes. This study analysed one-year changes in body compartments and their demographic and clinical determinants.

Methods

A prospective cohort of 112 adult kidney recipients transplanted between September 2020 and June 2022 at a Spanish tertiary hospital was followed. Body weight, muscle mass, fat mass, visceral fat and total body water were assessed by multi-frequency bioelectrical impedance at discharge, and at 3, 6 and 12 months. Associations with sociodemographic, clinical and comorbidity variables were examined using repeated-measures ANOVA and comparative tests.

Results

At 12 months, mean weight gain was 3.6 ± 6.5 kg (5.1%). Increases were greater in men, younger patients, non-dialysis candidates, those with previous transplantation and living donor grafts. Muscle mass rose during the first three months and then stabilised, with greater gains in men and haemodialysis patients. Fat mass decreased initially and then increased, particularly in women, younger recipients and living donor transplants. Visceral fat progressively increased after three months, with higher levels in men and older patients. Total body water declined in women, younger recipients and first transplant patients. Patients with new-onset diabetes gained less weight, while smokers gained more.

Conclusions

Post-transplant body composition is shaped by sex, age, BMI, comorbidities and donor type. Monitoring compartments beyond body weight may allow early detection of adverse metabolic trajectories. Tailored nutritional and lifestyle interventions are needed to optimise long-term outcomes.