NEW YORK (Reuters Health) - Night eating syndrome, characterized by a lack of appetite during the day and insomnia and increased appetite at night, may be caused by an abnormal response to stress, new study findings show.

"Night eaters have a different pattern of hormonal release to stress than normal eaters," lead study author Dr. Grethe S. Birketvedt of the University of Tromso in Norway told Reuters Health.

To investigate, Birketvedt and her colleagues studied stress hormone secretion patterns in five female night eaters and a comparison group of five women without the syndrome. The night eaters all consumed more than half of their daily food intake after 8 PM, and woke at least once during the night to eat.

The researchers injected the women with 100 micrograms of corticotropin-releasing hormone, which is released in response to stress and triggers the secretion of other stress hormones.

In general, the night eaters exhibited a gradual and slight increase in their stress hormones after the injection, followed by a gradual decrease, while their peers in the comparison group exhibited a rapid and significantly greater increase in their stress hormones, followed by a gradual decrease, the investigators report in the February edition of the American Journal of Physiology-Endocrinology and Metabolism. Thus the night eaters' hormone secretion in response to induced stress was significantly weaker than their peers'.

The study group was "worn out," Birketvedt explained. For example, their levels of the stress hormone cortisol at the beginning of the study were higher than those seen in the comparison group. "If (you are) stressed 24 hours a day, there will be no reaction when stress is induced," Birketvedt said.

In general, these findings indicate that "the relationship between the adrenal gland (which releases cortisol), the hypothalamus, where the appetite center is and the pituitary, where a lot of hormones are produced, is out of control," Birketvedt said. "No wonder they (night eaters) eat late at night and wake up during the night."

The researcher added, "With these findings we can find a treatment that turns the biological clock back to normal."

In the meantime, individuals with night eating syndrome "should try to think of what they eat before they go to bed," Birketvedt stated. She advised them to eat carbohydrate-rich foods before bed, stay away from sleeping pills or antidepressants, and take melatonin about 30 minutes before sleeping in order to lower their risk of night eating.

SOURCE: American Journal of Physiology-Endocrinology and Metabolism 2002;282:E366-E369.

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