Epicardial adipose tissue (EAT) is a type of visceral fat in the heart. It lies between the myocardium, the thick muscular layer of the heart muscle, and the pericardium, the thin sac that surrounds the heart. Unlike subcutaneous fat, which is under your skin, visceral fat surrounds your organs and can cause health problems.

EAT is associated with several heart conditions, including cardiovascular disease and abnormal rhythms called arrhythmias. Weight loss and certain medications can sometimes lower EAT levels and improve heart health.

EAT is an active fat because it is made up of active free fatty acids. Normal levels of EAT are helpful because the fatty acids play a key role in your heart’s metabolism. They help maintain energy production and keep the heart at a healthy temperature.

This layer of visceral fat can also protect the coronary arteries. A 2017 review of previous research also suggests that EAT secretes molecules called cytokines that regulate the function of the arterial walls, blood clotting, and inflammation.

However, too much of a good thing can be harmful. High levels of EAT can increase inflammation in the heart.

And because the visceral fat is right next to the myocardium, there is an increased risk of myocarditis, inflammation of the myocardium. According to a 2022 study, myocarditis is a major risk factor for arrhythmia.

In a separate 2022 study, researchers suggest that the buildup of EAT can cause your coronary arteries to narrow. This increases your risk of coronary artery disease, the most common form of heart disease. The study notes that as EAT levels rise, your body responds to the release of anti-inflammatory molecules by producing more pro-inflammatory molecules.

A 2017 report also notes that the EAT buildup isn’t just a risk factor for heart disease. It’s also a consequence. Damage to your heart can allow more adipose tissue to collect within the heart’s layers.

For people with type 2 diabetes, high levels of EAT may be particularly dangerous. Diabetes is an independent risk factor for heart disease, but greater EAT thickness may elevate the risk.

A 2020 study suggests that excess EAT tends to be more common in individuals with type 2 diabetes. The study also notes that this type of visceral fat is also associated with atherosclerosis (plaque buildup that narrows your arteries) and cardiovascular events, such as heart attack.

A 2022 study of more than 700 people also linked high levels of EAT with a greater risk of developing severe COVID-19 with cardiac complications.

Your doctor may not look for high levels of EAT unless you have diabetes or have been diagnosed with an arrhythmia or other cardiac condition. But your doctor can determine whether you have high levels of EAT using various types of cardiac imaging.

One commonly used and relatively low cost screening is transthoracic echocardiography (TTE). TTE uses sound waves to create computerized images of the heart and the network of blood vessels in the chest.

A standard CT scan or MRI may also reveal how thick EAT is in the heart. The greater the thickness, the higher the likelihood of complications.

A 2016 study of more than 100 adults suggests that the average EAT thickness in healthy people with no cardiac conditions was about 4.4 millimeters (mm). The average thickness for people who develop acute coronary syndromes (complications from reduced blood flow to the heart) was about 6.9 mm.

If your doctor determines that you have too much EAT and you are overweight, they may advise you to lose weight by exercising and eating a more balanced diet.

Medications, such as GLP-1 receptor agonists and SGLT2 inhibitors, may be prescribed to help reduce EAT levels. Doctors usually prescribe these medications to help treat diabetes and obesity.

Your doctor can use further imaging to check if you’ve reduced your EAT thickness. For many people, the combination of medications and a lifestyle that provides health-promoting benefits can reverse some of the complications triggered by excess EAT.

While you may not be able to see epicardial adipose tissue the way you can see belly fat, excess EAT can still pose risks to your heart health.

If testing shows that you have too much visceral fat around your heart, talk with your doctor about ways to reduce it and other steps you can take to protect your heart.