I find it fascinating that while asleep and in a prolonged fasting state, our blood sugar does not drop. A similar period of fasting, while awake, would result in drops in blood sugar and increases in appetite. However, why is it that when we sleep this does not occur?
The answer is due in part to a decrease in muscle movement and brain activity, especially during non-rapid eye movement (NREM) sleep, thus consuming less glucose. There is also an increased production of growth hormone in the beginning of the night and cortisol at the end–both of which promote the production of glucose from non-carbohydrate sources. Finally, there is an associated increased production of leptin, an appetite suppressing hormone during sleep. Together they work to prevent hypoglycemia and hunger while we sleep.
So what is going on with people who consume large amounts of their calories after bedtime? There are two forms of this condition. One is called Sleep-Related Eating Disorder and is a type of sleepwalking. It has been seen along with several medications such as Ambien (zolpidem), as well as in sleep disorders such as sleep apnea and restless legs syndrome. In this condition, there is usually total amnesia for the trips to the kitchen and eating. In fact, many of these people wake up with food in their bed, or stove burners left on and no recollection of what happened in the morning.
In the second form there is conscious but uncontrollable eating after bedtime. This is referred to as Nocturnal Eating Syndrome. It is not unusual for these people to consume over 50% of their daily caloric intake after bedtime. Both disorders are characterized by the high intake of simple sugars and fats, thus promoting obesity in many who exhibit these abnormalities.
The good news is that they are both treatable. In the case of Sleep-Related Eating Disorder, discontinuing the offending medication, or treating the primary sleep disorder can be curative. In the case of Nocturnal Eating Syndrome, cognitive behavioral therapy, properly timed light therapy, and in some cases, antidepressants that raise serotonin levels such as sertraline (Zoloft) have been effective. Therefore, if you or a loved one is a night eater, consciously or not, there are treatments available. Talk to your health care provider and if they are not familiar with this ask for a referral to someone who is.