Endothelial cell dysfunction, affecting the cells that line the blood vessels and control the ability of the vessels to expand and contract, is associated with an increased risk for coronary artery disease and cardiovascular events.  Virend K. Somers, from the Mayo Clinic (Minnesota, USA), and colleagues studied 43 healthy men and women, mean age 29 years, assessing for endothelial dysfunction  and tracking weight changes, for an eight-week study period.  Among those who gained weight in their abdomens (known as visceral fat), even though their blood pressure remained healthy, researchers found that the regulation of blood flow through their arm arteries was impaired due to endothelial dysfunction. Once the volunteers lost the weight, the blood flow recovered. Blood flow regulation was unchanged in the weight-maintainers and was less affected among those who gained weight evenly throughout their bodies. Observing that subjects who put on as little as 9 pounds (4 kilograms) of fat in the abdomen were at increased risk for developing endothelial cell dysfunction, the team concludes that: “In normal-weight healthy young subjects, modest fat gain results in impaired endothelial function, even in the absence of changes in blood pressure.”