Even a modest amount of weight gained around the middle can considerably heighten the risk of high blood pressure and related illness, says a new study.

Belly fat can affect the proper function of endothelial cells that line their blood vessels, increasing the risk for high blood pressure. These cells control the ability of the blood vessel to contract and dilate, which in turn facilitates blood flow.

Damage to the endothelium can lead to the vessel not functioning properly and eventually high blood pressure and blood vessel disease.

Therefore, "when people put on a modest amount of weight, and if the fat is in the belly, those people tend to have a greater impairment of endothelial function," says lead researcher Dr. Virend K. Somers, a professor of medicine at the Mayo Clinic School of Medicine. Endothelial function is a marker of health of the blood vessel.

"There is something about fat deposited in the belly that makes it potentially hazardous to health, because impaired endothelial function has been linked to increased risk of high blood pressure and blood vessel disease," Dr Somers says in the study, the findings of which have been published in the latest issue of the Journal of the American College of Cardiology.

In the study, Dr Somers and his associates randomly assigned 43 normal-weight adults to either gain about nine pounds or keep their current weight. The researchers specifically determined the ability of the brachial artery to dilate while measuring endothelial function in the artery which is located in the arm. They measure the artery before the study started, after eight weeks of weight gain and again after 16 weeks of weight loss.

People who gained weight showed a decrease in the ability of the artery to dilate, the researchers found. However, the investigators saw the ability of the brachial artery to dilate properly coming back to normal when they shed the weight again.

"It's only 10 pounds, and that's not much, but even this modest amount of weight gain has potentially harmful effects for blood vessels," Dr Somer's notes while observing that people tend to ignore minor weight gain, such as the few pounds they can put on over the holidays.