Abdominal fat may raise blood pressure

By Amy Norton

NEW YORK (Reuters Health) - Adults who carry most of their excess weight around the middle may be at particular risk of high blood pressure, new research shows.

In a 10-year study of Chinese adults, researchers found that those whose waistlines expanded over the years showed a similar increase in blood pressure.

Moreover, even young men and women who were abdominally obese at the start of the study, or who became so over time, were more likely to be diagnosed with high blood pressure.

The findings appear in the American Journal of Hypertension.

Research has shown that "apple-shaped" people are at greater risk of heart disease and type 2 diabetes than those whose extra pounds dwell largely on the hips and thighs. Studies have also suggested that general obesity raises the risk of high blood pressure, or hypertension.

But it hasn't been clear whether abdominal obesity, per se, can cause hypertension, Dr. Chen-Huan Chen, the study's senior author, told Reuters Health.

This study may be the first to "clearly show" that abdominal obesity predicts future hypertension, regardless of a person's current blood pressure or overall body weight, said Chen, a professor of medicine at National Yang-Ming University in Taipei, Taiwan.

It is possible, he noted, for a person to have a very large waistline but not weigh enough to be considered generally obese.

For their study, Chen and his colleagues followed 2,377 men and women age 30 and up for 10 years, during which time one-quarter developed high blood pressure. Those with large waistlines at the outset had a higher risk than their slimmer counterparts, as did people who became abdominally obese during the study period.

Even in a group of healthy adults ages 30 to 43 years, the researchers found that those whose waistlines expanded also saw their blood pressure increase.

Abdominal obesity often exists as part of a cluster of conditions known collectively as metabolic syndrome -- the other components being abnormal cholesterol levels, hypertension and insulin resistance, a precursor to type 2 diabetes.

It's a complex collection of heart risks, and it's not fully clear which problem might cause the others. But the current findings support the theory that abdominal obesity is the "true culprit" that spurs the development of insulin resistance, and then other components of metabolic syndrome, according to Chen.

If that's the case, he noted, "it is obvious that the most important thing to do is to prevent abdominal obesity, not just obesity."

There's no single definition of abdominal obesity, but in general, the waist sizes used to define metabolic syndrome are 35 inches or more for women and 40 inches or more for men.

SOURCE: American Journal of Hypertension, August 2006.