Abdominal obesity, reflected by increased waist circumference, is often accompanied by features of the metabolic syndrome, the authors explain, but the relative contributions of abdominal obesity versus hyperinsulinemia to high blood pressure are poorly understood.

Dr. Paul Poirier from Laval Hospital Research Center, Sainte-Foy, Quebec, Canada and colleagues investigated the contributions of excess adiposity (measured by BMI), abdominal fat accumulation (measured by waist circumference), fasting insulin level, and insulin sensitivity to the variation of resting blood pressure in 907 men and 937 women.

All four variables were significantly correlated with systolic blood pressure in men and women and with diastolic blood pressure in women, the authors report. Only BMI and waist circumference correlated significantly with diastolic blood pressure in men. In multivariate analyses, waist circumference was the best independent variable in explaining the variance of either diastolic or systolic blood pressure.

When men and women were classified into tertiles of fasting insulin and waist circumference, the researchers note, there was no association between variation in insulin and blood pressure once the variation in waist circumference was taken into account. "Results of the present study suggest that the well-documented association between obesity, fasting insulin, insulin sensitivity, and blood pressure may largely, if not entirely, be explained by phenomena related to the concomitant variation in the amount of abdominal fat, as estimated by a simple clinical parameter: waist circumference," the investigators write.

Dr. Poirier stated that, "Not all obese individuals are the same. We must target the obese at risk, which are the ones with abdominal obesity, low HDL and triglycerides above 1.7 mmol/L."

"We are looking at other populations to see if the conclusions are the same," he added.

"We should not neglect the possibility that visceral fat accumulation and hypertension may be parallel consequences of one or more common progenitor abnormalities," writes Dr. Ele Ferrannini from University of Pisa School of Medicine, Pisa, Italy in a related commentary. "Clearly, there is much research to perform before we fully understand how traveling along a wide circumference gets us to high blood pressure."

Source: Diabetes In Control.com: Hypertension 2005;45:347-348,363-367.