Arterial stiffness, central blood pressure and body size in health and disease.

BACKGROUND: Body size is associated with increased brachial systolic blood pressure (SBP) and aortic stiffness. The aims of this study were to determine the relationships between central SBP and body size (determined by body mass index (BMI), waist circumference and waist/hip ratio) in health and disease. We also sought to determine if aortic stiffness was correlated with body size, independent of BP. METHODS: BMI, brachial BP and estimated central SBP (by SphygmoCor and radial P2) were recorded in controls (n=228), patients with diabetes (n=211), coronary artery disease (n=184) and end-stage kidney disease (n=68). Additional measures of waist circumference and arterial stiffness (aortic and brachial pulse wave velocity (PWV)) were recorded in a subgroup of 75 controls (aged 51 ± 12 years) who were carefully screened for factors affecting vascular function. RESULTS: BMI was associated with brachial (r=0.30; P<0.001) and central SBP (r=0.29; P<0.001) in the 228 controls, but not the patient populations (r<0.13; P>0.15 for all comparisons). In the control subgroup, waist circumference was also significantly correlated with brachial SBP (r=0.29; P=0.01), but not central SBP (r=0.22; P=0.07). Independent predictors of aortic PWV in the control subgroup were brachial SBP (ß=0.43; P<0.001), age (ß=0.37; P<0.001), waist circumference (ß=0.39; P=0.02) and female sex (ß=-0.24; P=0.03), but not BMI. CONCLUSION: In health, there are parallel increases in central and brachial SBP as BMI increases, but these relationships are not observed in the presence of chronic disease. Moreover, BP is a stronger correlate of arterial stiffness than body size.

Variability in adherence to an unsupervised exercise prescription in obese women.

OBJECTIVE: To measure adherence to a specific exercise prescription (1500 kcal week(-1)) by objectively quantifying unsupervised exercise energy expenditure (ExEE) in obese women. DESIGN: The 16-week lifestyle intervention consisted of weekly meetings with research staff and promotion of increased ExEE (1500 kcal week(-1)) and a decreased dietary intake (-500 kcal day(-1)). PARTICIPANTS: Twenty-nine obese females (body mass index=36.8+/-5.0 kg m(-2), body fat=49.6+/-3.7%) from a hospital-based lifestyle intervention were included in the analysis. MEASUREMENTS: ExEE was estimated and monitored weekly using heart rate monitoring, and body composition was measured before and after the intervention by dual-energy X-ray absorptiometry. RESULTS: Free-living adherence to the exercise prescription was variable and, on average, modest such that 14% achieved 1500 kcal week(-1), and the average weekly ExEE (768 kcal week(-1)) represented 51.2% of the total amount prescribed. ExEE was correlated with changes in body weight (r=0.65, P<0.001) and fat mass (r=0.65, P<0.001). Achievement of a 5% weight loss target was dependent on the achievement of an ExEE level of 1000 kcal week(-1) (P<0.001). Exercise 'adherers' (>1000 kcal week(-1)) lost more weight (-9.9 vs -4.1 kg), more fat mass (-6.8 vs -3.0 kg) and more waist circumference (-9.8 vs -5.6 cm) when compared to 'non-adherers' (<1000 kcal week(-1)). DISCUSSION: Exercise is an integral component of lifestyle interventions aimed at reducing obesity and its complications. However, without accurate and objective measures of ExEE, it is difficult for relationships between exercise and health outcomes to be elucidated. The present study suggests an alternative to self-report to increase the confidence with which conclusions are drawn regarding the role of exercise within lifestyle interventions.