Washington: Are you overeating? It could be because you are stressed, says a new study. The relationship between diet, psychological stress and social and environmental factors is complex. Emory University researchers sought to determine whether individuals exposed to stress eat too much calorie-rich foods.

They studied the feeding patterns of female rhesus macaques, which are organised by a dominance hierarchy that maintains group stability through continual harassment and threat of aggression.

Such a structure is a constant psychological stress to subordinates, said Mark Wilson, who led the study.

During the study, female macaques were given access to a sweet but low-fat diet and a high-fat diet for 21 days each. For a 21-day period between each test diet, the group was given standard monkey chow.

To track feeding patterns, automated feeders dispensed a pellet of either the low fat or high-fat chow when activated by a microchip implanted in each female's wrist.

Researchers found socially subordinate females consumed significantly more of both the low-fat diet and the high-fat diet throughout a 24-hour period, while socially dominant females ate significantly less than subordinate animals and restricted their feedings to daytime hours.

This difference in feeding behaviour resulted in accelerated weight gain and an increase in fat-derived hormones in subordinate females. Wilson believes this may suggest profound changes in metabolism and the accumulation of body fat.

"As this study shows, they prefer the high-fat diet and, as a result of the stress of being a subordinate, they have higher levels of the hormone cortisol.

"This may be involved in the redistribution of fat to visceral locations in the body, something that is clinically associated with type II diabetes metabolic syndrome."

The findings of the study were published in the online edition of the journal Physiology and Behaviour. IANS