Resting metabolic rate is increased in hypertensive patients with overweight or obesity: potential mechanisms.

The purpose of this investigation was to determine whether differences in body composition, pharmacological treatment and physical activity explain the increased resting metabolic rate (RMR) and impaired insulin sensitivity in hypertension. Resting blood pressure, RMR (indirect calorimetry), body composition (dual-energy X-ray absorptiometry), physical activity (accelerometry), maximal oxygen uptake (VO2 max) (ergospirometry), and insulin sensitivity (Matsuda index) were measured in 174 patients (88 men and 86 women; 20-68 years) with overweight or obesity. Hypertension (HTA) was present in 51 men (58%) and 42 women (49%) (P = 0.29). RMR was 6.9% higher in hypertensives than normotensives (1777±386 and 1663±383 Kcal.d-1 , P = 0.044). The double product (systolic blood pressure x heart rate) was 18% higher in hypertensive than normotensive patients (P < 0.001). The observed differences in absolute RMR were non-significant after adjusting for total lean mass and total fat mass (estimated means: 1702 Kcal.d-1 , CI: 1656 - 1750; and 1660 Kcal.d-1 , CI: 1611 - 1710 Kcal.d-1 , for the hypertensive and normotensive groups, respectively, P = 0.19, HTA x sex interaction P = 0.37). Lean mass, the double product and age were the variables with the higher predictive value of RMR in hypertensive patients. Insulin sensitivity was lower in hypertensive than in normotensive patients, but these differences disappeared after accounting for physical activity and VO2 max. In summary, hypertension is associated with increased RMR and reduced insulin sensitivity. The increased RMR is explained by an elevated myocardial oxygen consumption due to an increased resting double product, combined with differences in body composition between hypertensive and normotensive subjects.