Fat, especially abdominal fat, secretes angiotensin which makes angiotensin II, a powerful vasoconstrictor that also directs the kidneys to absorb more sodium so blood vessels retain more fluid volume, says Dr. Harshfield, who is principal investigator on a separate National Institutes of Health grant looking at how fat contributes to high blood pressure. Research he published in 2003 in Hypertension also shows that overweight boys have greater blood pressure increase in response to stress than their female peers and decreased ability to return to normal.
For the newly published study, researchers measured the blood pressure of study participants every 15 minutes throughout a two-hour baseline period, an hour of competitive video games and a two-hour recovery period.
They found that while blood pressure increased an appropriate average of 5 percent in response to the stress of video games, participants who had more lean muscle mass than fat were better able to return to normal levels through this sodium excretion process called natriuresis.
Previous studies by Dr. Harshfield have shown that race also contributes to elevated pressures following stress because of blacks' reduced ability to excrete sodium. The new study shows that high body fat is another independent predictor of the abnormal response.
"The major finding of this study is that body composition is related to the pressure natriuresis response to mental stress," the researchers write. "Specifically, (lean body mass) was associated with higher (blood p
Contact: Toni Baker
Medical College of Georgia