The aim of this study was to examine the association between BMI categories, stratified by metabolic health status, and the risk of kidney function decline (KFD).

In this study, 42,128 adult patients with a stable BMI were classified over a 3‐year baseline window by BMI and metabolic health status (assessed by Adult Treatment Panel‐III criteria). KFD was defined as an estimated glomerular filtration rate (eGFR) decline ≥ 30%, eGFR < 15 mL/min/1.73 m², or receipt of dialysis and/or transplant.

Over a median of 5.1 years (interquartile range 2.1‐8.9), 6,533 (15.5%) individuals developed KFD. Compared with the normal weight, metabolically healthy category, metabolically healthy obesity was associated with a higher risk of KFD (adjusted hazard ratio [aHR] 1.52; 95% CI: 1.22‐1.89). aHRs for KFD were 1.17 (95% CI: 0.89‐1.53), 2.21 (95% CI: 1.59‐3.08), and 2.20 (95% CI: 1.55‐3.11) for metabolically healthy obesity with BMI 30 to 34.9, BMI 35 to 39.9, and BMI ≥ 40 kg/m². These associations were consistent among men and women, patients with eGFR ≥ or < 90 mL/min/1.73 m², and age ≥ or < 55 years. The risk of KFD was highest among metabolically unhealthy individuals with BMI ≥ 40 (aHR 4.02; 95% CI: 3.40‐4.75 vs. metabolically healthy individuals with normal weight).

Obesity, whether in the presence or absence of metabolic health, is a risk factor for KFD.