Healthy Weight, Rather Than Fitness, Most Important for Preventing High Blood Pressure

From Heartwire

Michael O'Riordan

July 19, 2010 (Dallas, Texas) — Individuals who have a healthy body weight are more likely than those who are physically fit to have lower blood pressure, according to the results of a new study [1]. In a comparison of fitness vs fatness, body mass index (BMI) was more important than cardiorespiratory fitness for predicting systolic blood pressure, report researchers.

"Our findings suggest that achieving normal-weight status should be the primary goal for hypertension prevention, and only modest levels of cardiorespiratory fitness are needed to obtain optimal blood pressure among individuals who are normal weight," write Dr Jennifer Chen (University of Texas Southwestern Medical Center, Dallas) and colleagues in the July issue of the American Heart Journal.

The results are from the Cooper Center Longitudinal Study, an analysis of 35 061 patients presenting to a clinic for a comprehensive medical examination between 1990 and present. The purpose of the study was to analyze the relative importance of BMI and cardiorespiratory fitness on systolic blood pressure. Studies have shown that exercise and cardiorespiratory fitness are associated with lower hypertension risk, including reductions in systolic blood pressure of 3 or 4 mm Hg with exercise training.

"A key unanswered question is whether hypertension prevention should be focused on weight control by any acceptable intervention, or whether cardiorespiratory fitness, independent of BMI, is a more important first target for prevention of hypertension," explain the researchers.

In this cohort, consisting mainly of white men (average age, 46 years), normal-weight individuals had a mean systolic blood pressure 12 mm Hg lower than obese individuals (115 vs 127 mm Hg, p<0.001). In contrast, individuals with high levels of fitness, those in the highest quartile, had a 6 mm Hg lower systolic blood pressure than those least fit (119 vs 125 mm Hg, p<0.001).

When assessing BMI and cardiorespiratory fitness concurrently, there was a significant increase in systolic blood pressure by BMI quartile for every level of fitness, including those with low and high levels of fitness. However, level of fitness was associated with blood pressure only in individuals with the lowest and highest BMI, not in women with BMIs of 21 to 27 kg/m2 or men with BMIs of 25 to 30 kg/m2 (BMI quartiles 2 and 3).

The researchers point out that obesity might be such an important determinant of hypertension that the benefits of other lifestyle factors are not obtained until individuals get down to a healthy weight. They also note that the beneficial effects of exercise on blood pressure are modest in obese subjects because of the "competing effects of obesity on vascular and metabolic pathways," including the effects on arterial compliance, sympathetic activity, insulin sensitivity, vascular resistance, and release of endothelium-derived nitric oxide.

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