Even modest weight gain can cause damage, according to a report in the Journal of the American College of Cardiology. Forty-three participants of a normal, healthy weight were asked to either gain 4 kg (about 9 pounds) or maintain their current weight over a period of 16 weeks.

Those that gained weight experienced “impaired endothelial function, even in the absence of changes in blood pressure.” It was the visceral fat (fat that surrounds the organs), not the subcutaneous fat (the thin layer of fat under the skin) that had the greatest effect on cell function.

Dr. Virend K. Somers of the Mayo Clinic School of Medicine says endothelial function is a good indicator of blood vessel health.

“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,” he told Health Day.

Endothelial cells line the insides of blood vessels. When these cells dysfunction, blood vessels and arteries may have difficulty contracting. This can cause high blood pressure and, further down the road, cardiovascular disease. Good reason to lose weight, right? The good news is endothelial cells begin to function normally following weight loss.

Want to learn more about how belly fat (visceral fat) affects your body? Visit Mayo Clinic. You can also read the full story by Health Day or see the report in the Journal of the American College of Cardiology.