Mediterranean diet as a strategy for preserving kidney function in patients with coronary heart disease with type 2 diabetes and obesity: a secondary analysis of CORDIOPREV randomized controlled trial

BACKGROUND: Type 2 diabetes mellitus (T2DM) is an independent risk factor for chronic kidney disease (CKD), but the impact of concomitant obesity on kidney dysfunction and response to dietary strategies is unclear. This study aimed to clarify how obesity contributes to kidney function among patients with T2DM and coronary heart disease (CHD) to identify the most effective dietary approach to preserve kidney function. METHODS: 1002 CHD patients with eGFR ≥ 30 ml/min/1.73 m² were randomized to a Mediterranean diet (35% fat, 22% MUFA, <50% carbohydrates) or a low-fat diet (28% fat, 12% MUFA, >55% carbohydrates). Patients were categorized into four groups by T2DM and obesity status. Kidney function was assessed by serum creatinine-based estimated glomerular filtration rate (eGFR) and urinary albumin-to-creatinine ratio (uACR) at baseline and after 5 years. RESULTS: At baseline, Obesity/T2DM patients had the lowest eGFR and highest uACR versus non-diabetics (p < 0.05). Over 5 years, the Mediterranean diet produced a smaller eGFR decline than the low-fat diet in Obesity/T2DM patients (p = 0.014), but not in other groups, with an eGFR decline 2.698 ml/min/1.73 m² lower versus low-fat (p = 0.032). The Mediterranean diet also reduced uACR only in Obesity/T2DM (p = 0.024). CONCLUSIONS: Obesity adds to T2DM in worsening kidney function. In patients with both T2DM and obesity, a Mediterranean diet appears more beneficial than a low-fat diet for preserving kidney function, supporting personalized lifestyle strategies in secondary cardiovascular prevention. TRIAL REGISTRATION: http://www.cordioprev.es/index.php/en; ClinicalTrials.gov NCT00924937.