Hypertension

Data from NHANES III show that the age-adjusted prevalence of high blood pressure increases progressively with higher levels of BMI in men and women (Figure 2) (2).

Figure 2.  NHANES III Age-Adjusted Prevalence of
Hypertension* According to Body Mass Index

* Defined as mean systolic blood pressure 140mm Hg, mean diastolic as 90mm Hg or currently taking anti-hypertensive medication.
Source: Brown C., et al. Body Mass Index and the Prevalence of Risk Factors for Cardiovascular Disease (submitted for publication).

High blood pressure is defined as mean systolic blood pressure 140 mm Hg, or mean diastolic blood pressure 90 mm Hg, or currently taking anti-hypertensive medication. The prevalence of high blood pressure in adults with BMI 30 is 38.4 percent for men and 32.2 percent for women, respectively, compared with 18.2 percent for men and 16.5 percent for women with BMI < 25, a relative risk of 2.1 and 1.9 for men and women, respectively. The direct and independent association between blood pressure and BMI or weight has been shown in numerous cross-sectional studies (3-5), including the large international study of salt (INTERSALT) carried out in more than 10,000 men and women (6). INTERSALT reported that a 10 kg (22 lb) higher body weight is associated with 3.0 mm Hg higher systolic and 2.3 mm Hg higher diastolic blood pressure (6). These differences in blood pressure translate into an estimated 12 percent increased risk for CHD and 24 percent increased risk for stroke (132). Positive associations have also been shown in prospective studies (76-80).

Obesity and hypertension are comorbid risk factors for the development of cardiovascular disease. The pathophysiology underlying the development of hypertension associated with obesity includes sodium retention and associated increases in vascular resistance, blood volume, and cardiac output. These cardiovascular abnormalities associated with obesity are believed to be related to a combination of increased sodium retention, increased sympathetic nervous system activity, alterations of the renin-angiotensin system and insulin resistance. The precise mechanism whereby weight loss results in a decrease in blood pressure is unknown. However, it is known that weight loss is associated with a reduction in vascular resistance and total blood volume and cardiac output, an improvement in insulin resistance, a reduction in sypathetic nervous system activity, and suppression of the activity of the renin angiotensin aldosterone system (764-769).