I have seen a number of new studies on the dangers of epicardial fat (fat around the heart). This new study links epicardial fat to the presence and severity of heart disease.
As to reducing it, diet works okay, but exercise works substantially better.
This matches up with another study I found. It shows a reduced waist circumference is linked to better health but primarily if it is matched with exercise. In other words, if you get a lean waist by diet, it will improve your health some, but it you get a lean waist via exercise than it seems to be really beneficial.