The study was conducted primarily on monkeys, but researchers say the results would be very similar for humans.
When female monkeys were housed in groups, a "pecking" order was formed. Subordinate monkeys were often left out of group activities and were the target of aggression. These monkeys developed more fat in the stomach than dominant monkeys.
This abdominal fat increases the buildup of cholesterol and fat in the arteries, which can lead to heart disease.