'Much of the excess fat in many people who are overweight is located in the abdomen, and that fat behaves differently than fat in other locations,' said Carol A. Shively, principal study investigator, Wake Forest University School of Medicine (WFUSM).

'If there's too much, it can have far more harmful effects on health than fat located in other areas,' said Shively.

Shively and colleagues found that women and female monkeys have a natural protection against heart disease -- women typically develop heart disease, on average, 10 years later than men do.

That protection seems to be lost when stress and visceral fat increase. Researchers found that the monkeys with high social stress and larger amounts of visceral fat also had ovaries that produced fewer protective hormones.

The study appeared in the current issue of Obesity.