Yesterday I started a new diet using intermittent fasting. For this reason I only ate one meal all day. I was pretty surprised how well I passed that day: I studied a lot, did some sports and fulfilled several programming exercises from university. After sports I had my first meal. Overall—a great day without any side effects from the intermittent fasting.

However, at 11 PM I went to bed. There I realized that I was not tired. So I read a book. One hour passed—still no feeling of fatigue. So, I thought, some push ups will make me tired. Nope, the push-ups did not work. It was already 1 AM, and I had to get up early. I decided to use my strongest means, which I only use before big exams: a glass of brandy. No effect! Meditation—nope. After that, 30 minutes of running outside in the cold—again, no effect. At 4 AM I decided to get up and study.

A weird experience. I know that I lack sleep; nevertheless, I can study and concentrate.

I Googled the keywords fastening and sleeplessness. Then I realized that it is a common pattern that some people sleep less during fasting.

Why is fasting related to insomnia?

  • $\begingroup$ having read the answers here I'm not sure whether to be concerned about the insomnia...is the increase in adrenalin or orexin detrimental to my long term health or is it a part of what makes intermittent fasting beneficial? $\endgroup$
    – user6675
    Commented Sep 4, 2014 at 0:26
  • $\begingroup$ I used to be a bit of a gym rat. I adopted intermittent fasting; Eat for hrs then fast for 16 (including sleep). In practical terms this meant I got into a habit of stopping eating at 4pm. I had major sleep problems emerge but I did not connect them to how I ate. The past year, my sleep declined to 5hrs a night, the past month 4hrs - I had intermittent insomnia. I could not get back to sleep for 2 or 3 hours and the poor sleep after I woke was more like intermittent drowsing. Fixed this with a banana milkshake and 1/4 of a grated nutmeg at 8pm with 100g of milk and cereal (16g of sugar). Only $\endgroup$
    – muscleriot
    Commented Mar 19, 2018 at 16:33
  • $\begingroup$ mod addition (continued comment from @muscleriot): ...*been a few days so far but the difference has been dramatic. I use a Sleep Monitor and even my deep sleep has increased to over 2hrs of my now 6hr sleep.* $\endgroup$
    – AliceD
    Commented Mar 19, 2018 at 19:27

2 Answers 2


Fasting causes stress and makes your body work off of fat rather than sugar. Sugar is of course related to insulin, which even in normal (non-diabetic) people must be maintained at a certain level (Kaditis et al., 2005). Without a proper level of insulin, your body will upregulate orexin in the brain until you eat (Willie, Chemelli, Sinton, & Yanagisawa, 2001). Orexin will give you artificial energy and inhibit sleep.


Kaditis, A. G., Alexopoulos, E. I., Damani, E., Karadonta, I., Kostadima, E., Tsolakidou, A., ... & Syrogiannopoulos, G. A. (2005). Obstructive sleep‐disordered breathing and fasting insulin levels in nonobese children. Pediatric Pulmonology, 40(6), 515–523.

Willie, J. T., Chemelli, R. M., Sinton, C. M., & Yanagisawa, M. (2001). To eat or to sleep? Orexin in the regulation of feeding and wakefulness. Annual Review of Neuroscience, 24(1), 429–458.

  • 1
    $\begingroup$ Excerpts [emphasis added] from Willie and colleagues (2001): "Orexin mRNA expression is upregulated by fasting and insulin-induced hypoglycemia...Orexins...significantly increase food consumption, wakefulness, and locomotor activity in rodent models... disruption of the orexin gene in mice produces a syndrome remarkably similar to human and canine narcolepsy, a sleep disorder characterized by excessive daytime sleepiness, cataplexy, and other pathological manifestations of the intrusion of REM sleep-related features into wakefulness..." $\endgroup$ Commented Jan 28, 2014 at 8:19
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    $\begingroup$ And, "These findings suggest that the orexin neuropeptide system plays a significant role in feeding and sleep-wakefulness regulation, possibly by coordinating the complex behavioral and physiologic responses of these complementary homeostatic functions." All from the abstract. Nice find! $\endgroup$ Commented Jan 28, 2014 at 8:20
  • $\begingroup$ It's rat research, but it probably applies. It emphasizes how another component of the homeostatic equilibrium between the sympathetic and parasympathetic nervous systems can be upset by fasting. Resting but not digesting sends mixed signals to our poor, simple-minded neurochemical system. Have some pity, and don't confuse it! $\endgroup$ Commented Jan 28, 2014 at 8:25

One thing worth pointing out as a very terse hint of an answer: we all know that activation of the sympathetic nervous system is often referred to as the "fight-or-flight response," but parasympathetic nervous system (PNS) activation is less commonly known as the "rest-and-digest" response...though this does appear on Wikipedia's PNS page. Eating (or maybe just having fresh food in the early parts of one's gastrointestinal tract; I'm not sure) activates the PNS, which itself has soporific effects.

Also, a separate quote from the Hypoglycemic Health Association relating starvation to adrenaline production [emphasis added]:

When the brain is threatened with energy starvation it will send a hormonal message to the adrenal glands to pour adrenaline into the system. Adrenaline is a hormone that converts glycogen – strings of glucose molecules stored in the body – back into glucose, so as to feed the brain again. (See image). But abnormal adrenaline secretion during the night can also cause insomnia and nightmares...

If we are able to supply the body with all the nutrients, enzymes, coenzymes, vitamins and minerals, it will have all the ingredients to synthesize the necessary neurotransmitters and hormones that can make us feel happy and content when we should. A natural diet should provide us with all the components to build the necessary serotonin and melatonin to enable us to sleep.

This is from "The Biochemistry of Insomnia," which may interest you more broadly, but I think I've quoted most of the content that pertains directly to diet here.

Edit: BTW, you might also find this question of interest (I've answered it somewhat similarly):
The effect of proper food intake on emotions and brain function


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