Too often, excess fat in any part of the body is viewed in the same way. But researchers know that all fat is not created equal.

In fact, doctors have known for some time that the layer of fat that surrounds our organs can be particularly deadly.

Now there is new evidence that when fat surrounds the left coronary artery, it may help to kick off atherosclerosis, the disease process that narrows the coronary arteries, which can lead to a heart attack.

Researchers recently presented a study using mice to demonstrate the dangers of this type of fat. The researchers transplanted this inflamed fat from high-fat eating obese mice and transplanted it to the carotid arteries of lean mice. In doing this, they discovered that this fat tissue promptly damaged the blood vessel wall and caused heart disease symptoms to form there.

This research shows that “various secreted factors, or signals” from the perivascular fat of the obese mice negatively affected the functions of the blood vessel wall in the lean mice, lead author Tapan Chatterjee, Ph.D., said in a presentation at the American Heart Association’s Atherosclerosis, Thrombosis, and Vascular Biology 2012 Scientific Sessions.

This study underscores the importance of not only being lean, but also eating lean as well.