Although visceral fat makes up only a small proportion (around 10%) of body fat, it is a key player in a variety of health problems. It’s because visceral fat surrounds and puts pressure on your internal organs such as your heart, liver, kidneys, intestines, and pancreas. The higher the amount of visceral fat a person stores, the more at risk they are for certain health complications.

Research suggests that fat cells — particularly abdominal fat cells — are biologically active. We can think of fat as an endocrine organ or gland, producing hormones and other substances that can profoundly affect our health. Although scientists are still deciphering the roles of individual hormones, it’s becoming clear that excess body fat, especially abdominal fat, disrupts the normal balance and functioning of these hormones.

Scientists are also learning that visceral fat pumps out immune system chemicals called cytokines that can increase the risk of cardiovascular disease. These and other biochemicals are thought to have damaging effects on cells’ sensitivity to insulin, blood pressure, and blood clotting.

Another reason excess visceral fat is so harmful could be its location near the portal vein, which carries blood from the intestinal area to the liver. Substances released by visceral fat, including free fatty acids, enter the portal vein and travel to the liver, where they can influence the production of blood lipids. Visceral fat has been directly linked with higher total cholesterol and LDL (bad) cholesterol, lower HDL (good) cholesterol, and insulin resistance.