Being only a bit overweight -- or even on the high side of "normal" -- may increase the risk of developing high blood pressure over the years, according to a report in the American Journal of Hypertension (volume 20, page 370).

People who are over weight or obese are more likely to have high blood pressure than people without weight problems. One reason is that the more weight you have, the more blood your body needs to carry oxygen and nutrients to your organs and tissues. As blood volume increases, so does the pressure against the artery walls, thus raising blood pressure.

Now an analysis of data from the Physicians Health Study looked at the relationship between body mass index (BMI) and blood pressure in more than 13,000 middle-aged and older men followed for over 15 years. The higher the men's BMI at the outset of the study, the higher their risk of developing high blood pressure over the years. In addition, the risk increased as weight increased, even after taking into consideration other possible contributing factors such as age, smoking, physical activity, diabetes, and high cholesterol.

What's more, it didn't take many extra pounds to raise the risk of high blood pressure. Even men with a normal BMI of between 22 and 24 -- albeit on the high side of normal -- were 20% more likely to develop high blood pressure than those with a BMI of under 22.

In comparison, overweight and obese men (BMI of greater than 26) were 85% more likely to have high blood pressure. So preventing weight gain, even small amounts, can lower the risk of developing high blood pressure in men -- and, most likely, in women as well.