Stress Hormones Drive Night Eaters

Feb. 12, 2002 -- Find yourself raiding the refrigerator in the middle of the night? Turns out that it may be your body's response to stress that has gone awry -- compelling you to eat when you're not even really hungry.

It's not exactly clear how many people have night eating syndrome. Estimates are around 1%-2% of adults, but some have suggested up to a quarter of people who are overweight by at least 100 pounds eat this way.

Night eaters typically have little or no appetite for breakfast. They eat more than half of their daily food after dinner but before breakfast and are often upset about how much was eaten the night before.

Night eaters feel tense, anxious, upset, or guilty while eating and at night. They have trouble falling asleep or staying asleep and often wake frequently to eat. Night-eating syndrome involves continual eating throughout evening hours. This eating produces guilt and shame, not enjoyment.

Night eating syndrome is currently not an official eating disorder. Previous research has indicated that it may be related to a disruption in your body's 24-hour clock -- called the circadian rhythm.

Another main regulator in your body is a hormone system called the HPA axis, which also coordinates many of your body's functions -- including its response to stress. The association between these two systems is not well understood, so researchers wanted to see if a problem with the HPA axis might also be behind night eating syndrome.

Lead researchers Grethe S. Birketvedt and colleagues studied five women with night eating syndrome. The women consumed over 50% of their daily food after 8 p.m. and woke up at least once during the night to eat. Their hormone levels produced by the HPA axis were compared to women who weren't night eaters.

The study results are featured in the February issue of American Journal of Physiology - Endocrinology and Metabolism.

During the seven-day study, the women identified as night eaters woke up more than three times per night, on average. The comparison group did not wake up at night to eat.

During the study, all of the women were given a hormone to stimulate their HPA axis. But in the night eaters, their cortisol levels didn't go as much as the comparison group.

The results suggest that night eaters have an abnormal stress response caused by a hormone abnormality in their HPA axis, according to the researchers.

Plus, they say that the altered sleep and appetite pattern may be explained by this abnormal hormone response. Several other eating disorders, such as obesity, anorexia, and bulimia, have also been linked to abnormalities in the HPA axis.