Relation of central hemodynamics to obesity and body fat distribution

Central obesity increases the risk for cardiovascular disease, but little is known about its hemodynamic effects. The aims were to investigate the influence of obesity (as defined by body mass index) and abdominal fat accumulation (as defined by the waist/hip ratio) on hemodynamics at rest and during mental stress. Invasive hemodynamic studies were performed in 20 healthy, normotensive young men (aged 18-22 years) recruited from an unbiased population sample. Their body mass index and waist/hip ratio ranged between 18.5 and 30.2 (mean 24.1) and 0.77 and 0.98 (mean 0.87), respectively. Hemodynamics were related to the two anthropometric indexes by bivariate regression analyses. Cardiac output and stroke volume were positively correlated to body mass index (p = 0.05 and p = 0.005), but inversely to waist/hip ratio (p = 0.01 and p = 0.01). Mental stress augmented the hemodynamic patterns. Total peripheral resistance during stress correlated inversely to body mass index (p = 0.02), whereas high waist/hip ratio was associated with higher systemic vascular resistance p = 0.002). The delta CO/delta MAP ratio, i.e., relative contribution of cardiac output for the stress-induced increase in mean arterial pressure, showed a strong positive association with body mass index (p = 0.004), but was inversely related to the waist/hip ratio (p = 0.002). Serum insulin correlated significantly to the stress-induced change in total peripheral resistance (r = 0.54; p = 0.02), whereas the increase in cardiac output was inversely related to insulin (r = -0.59; p = 0.007). Thus, central obesity is associated with a specific hemodynamic pattern characterized by higher total peripheral resistance, lower cardiac output, and a vasoconstrictor response to psychosocial stress.