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

## TL;DR

This study tracks body composition changes in kidney transplant patients over one year and finds that factors like sex, age, and donor type influence weight and muscle/fat changes.

## Contribution

The study provides new insights into how specific demographic and clinical factors influence body composition changes after kidney transplantation.

## Key findings

- Mean weight gain at 12 months was 3.6 ± 6.5 kg, with greater increases in men, younger patients, and living donor recipients.
- Muscle mass increased initially and stabilized, while fat mass decreased first and then increased, especially in women and younger recipients.
- Visceral fat increased after three months, particularly in men and older patients, and total body water declined in women and younger recipients.

## Abstract

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.