Baseline and follow-up association between adiposity and renal function: data from the ILERVAS cohort

Introduction: Obesity is multifactorial and increasingly prevalent disease associated with chronic kidney disease (CKD). While cross-sectional studies support a link between adiposity and renal dysfunction, the long-term impact of total body fat on kidney function remains unclear. This study aims to evaluate the association between baseline adiposity, assessed by body mass index (BMI) and total body fat percentage, and renal function parameters, and to determine whether adiposity predicts CKD outcomes over 4-years in individuals without diabetes at low-to-moderate cardiovascular risk. Methods: This retrospective, multicenter study included 8 153 participants from the ILERVAS project in Lleida, Spain. Adiposity was measured using BMI and estimated body fat percentage (CUN-BAE formula). Renal function was evaluated by estimated glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR). A subset of 3 222 individuals was re-evaluated after four years. Multivariable regression models and ROC analysis were performed to explore associations and predictive performance. Results: CKD prevalence was 15.1%, higher in individuals with obesity (17.2%) than in those with overweight (13.7%) or normal weight (13.9%, p<0.001). Body fat percentage showed a stronger inverse correlation with eGFR than BMI and was independently associated with eGFR decline. Baseline body fat percentage and its increase over time were associated with eGFR decline. Neither adiposity measure independently predicted CKD presence nor albuminuria. Conclusions: Higher total body fat is associated with impaired renal function and its progression over time, independently of traditional CKD risk factors. These findings support incorporating body fat assessment in CKD prevention beyond BMI-based strategies.