A new study says that even a weight gain of nine pounds can affect how well the body's blood vessels function.

The team from the Mayo Clinic School of Medicine divided 43 healthy, normal weight people (average age: 29) into two groups: the first one was told to gain about nine pounds, and the second, to maintain their current weights. Blood vessel health was analyzed by a test called flow-mediated dilation (FMD), which essentially measures how well the endothelial cells of the blood vessels are working as they contract and dilate to let blood flow through.

After the weight-gainers lost the weight they had gained in the first part of the study, their blood vessel function returned to baseline (what it was when they started).

As expected, after participants had gained the weight, their blood vessel function declined, compared to the people who maintained their weight. This suggests that even what most would consider a small weight gain can actually affect our cardiovascular systems in important ways. But there's some good news, too: After the weight-gainers lost the weight they had gained in the first part of the study, their blood vessel function returned to baseline (what it was when they started).

Did it matter where in their bodies people gained the weight? You bet. The relationship between blood vessel function and weight gain was much stronger for belly fat than it was for subcutaneous (evenly distributed) fat. Belly fat has already been linked to a variety of health problems, like heart disease and diabetes, and people who tend to gain weight around their middles are often encouraged by their doctors to lose it, in order to avoid some of these problems.

Virend K. Somers and his team say that many people gain weight at certain times of the year, and we tend to consider it an "accepted consequence the holiday season". They say that their "study provides evidence that modest fat gain affects endothelial function" and that we, as a culture, shouldn't consider "going up a clothing size" such an innocent problem.

So if you need to lose a few pounds, it's probably a good idea to get going. Especially if you tend to gain weight around your middle, as many of us do, shedding those extra pounds can only help your heart.

The research was published in the Journal of the American College of Cardiology on August 17, 2010.