The aim of this study was to evaluate whether body mass index (BMI) is independently correlated with plasma aldosterone concentration (PAC) in treated essential hypertensive patients, and whether the relationship between BMI and high blood pressure (BP) can be partially mediated by PAC despite renin–angiotensin–aldosterone system blockade.

This study used a cross-sectional design and included 295 consecutive essential hypertensive patients referred to our centre for uncontrolled BP despite stable antihypertensive treatment for at least 6 months. The main exclusion criteria were age >65 years; glomerular filtration rate <30 ml/min; and therapy with mineralocorticoid receptor antagonists, direct renin inhibitors, amiloride or oral contraceptives.

Higher levels of obesity showed a significantly higher mean PAC with a steep nonlinear increase in patients with BMI ≥35 kg/m². Class 2 and 3 obese patients had a higher mean PAC than nonobese and class 1 obese patients, even in patients under stable treatment with either angiotensin-converting enzyme inhibitors (ACEIs) or angiotensin receptor blockers (ARBs). In a stepwise multiple linear regression model, only log of plasma renin activity (PRA), mean blood pressure (MBP), and class 2 and 3 obesity showed an independent correlation with PAC. In the same model applied to patients treated with ACEIs or ARBs, only logPRA and class 2 and 3 obesity showed a direct correlation with PAC.

In treated essential hypertensive patients, a BMI ≥35 kg/m² is independently, albeit modestly, correlated with PAC. The correlation between BMI ≥35 kg/m² and PAC holds true even in ACEI/ARB-treated patients. Further study is required to determine whether the association of obesity with BP is mediated by PAC in hypertensive patients on stable therapy with ACEIs or ARBs.