by Siim Land
Compared to eating sporadically and with a 15+ hour eating window, time restricted feeding in the evening or later in the day is still much better for your general health and longevity than having your food without timing it.
Furthermore, resistance training also makes the body more efficient with the food you consume. The best time for heavy physical exercise like lifting weights according to the circadian rhythm is in the afternoon around 4-6 PM. That’s when your coordination and strength tend to peak. Having a workout and then eating afterwards should have no significant negative side-effect on your long-term health or body composition.
Theoretically, if you spend the entire day fasting, then you’re suppressing your food circadian rhythm and only activating it in the evening when you’re starting to eat. However, the circadian rhythms are persistent, meaning they persist even in constant darkness with a period of about 24 hours. The clocks are always running. Whether or not you’re in sync with them depends on the cues you receive from your environment.
There are different things that can offset the food circadian rhythm without having to break the fast. Drinking water and things like coffee also stimulate certain metabolic processes in the liver which can then set off the liver’s circadian rhythm. You don’t need to be eating a lot of calories to trigger the circadian processes or to affect it. The same is with light – even just a tiny bit of blue light at night time can already suppress melatonin production and inhibit your sleep quality. Autophagy as well - even just a small amount of calories will break autophagy and start the feeding cycle.
When it comes to OMAD and eating most of your food later in the day, then I would say it’s not going to have any negative effect on the circadian rhythm directly because it’s not the most influential factor. Light and movement are much more powerful signals of circadian rhythms and eating food later in the day will be used based on the physical conditions of the body i.e. how insulin sensitive you are at that point, what’s your glycogen status, and how long you’ve been fasting.
Fasting can only have a negative impact on circadian rhythms and your health if it’s going to disrupt your sleep. If you eat too much food too close to bedtime, then your gut is going to have to spend extra energy on digestion. This can make you sleep worse, preventing your brain from going into deeper stages of sleep.
During the night, the body would naturally start to cool itself down as to preserve energy and go into repair mode. However, eating and digesting food raises your core temperature, which takes away energy from the repair processes. It can also cause bloating, constipation, weight gain, and other digestive issues because in order to break down food and digest it, you need to produce a lot of stomach acid and enzymes.
If you eat a ton of food and then lay on your back for the coming night, then you may get acid reflux, you may stop producing hydrochloric acid, which may stop all digestive processes as well. While you’re sleeping, the food will then start to sit there and you’ll only start digesting it when you wake up the next morning. This will make you feel like you’re in a food coma because (1) you didn’t get enough deep sleep, (2) you’re still digesting the food from the night before, and (3) certain foods may have begun to ferment in the small intestine, especially fructose and carbohydrates, because they got stuck there for the entire night, which then can cause leaky gut and brain fog.
So, it’s not a good idea to be eating immediately before going to bed. That’s why people eating later at night may not gain all the benefits of glucose control and insulin sensitivity. It depends on what you ate and what macronutrients there are but you should expect to digest the food for at least 4 hours. The optimal time frame to stop eating before sleep would be about 2-4 hours.
What you also want to do is spend a little bit of time moving around after eating. Walking is one of the best ways of lowering your post-prandial blood sugar, promoting digestion, increasing nutrient absorption, and helping with gastric emptying. I recommend going for a slow and steady walk for 10-15 minutes after dinner as to speed up digestive processes. This shouldn’t be a type-A speed-walking stroll or anything hyped up. If you push it too much you’ll trigger the sympathetic nervous system, which will actually shut down digestion again.
How to Not Disrupt the Circadian Rhythms with Fasting
Coming back to the circadian rhythms. To make sure you’re not causing any mismatch with your chronobiology, you’d want to ensure you have the other circadian signaling factors on point.
Expose yourself to natural daylight in the morning for at least 5-10 minutes. That’s going to offset the right processes via the suprachiasmatic nucleus in the brain. You’ll sleep better at night, you’ll have a better mood, and you’ll start the metabolism as well to a certain extent.
After waking up get moving – Do some mobility exercises, go for a walk, shake yourself, rebounding, and do breathing exercises. Movement is also a powerful circadian cue.
During the day, restrict your caffeine intake. The half-life of caffeine is 4-6 hours, which means that if you drink coffee at noon, 50% of it will still be in your system at 5 PM. That’s why the last time you can safely ingest caffeine is 1-2 PM. After that, you may decrease your sleep quality. Also, I would actually recommend everyone to postpone their coffee intake all the way until noon because you shouldn’t need caffeine to wake yourself up in the morning. When you wake up, you should feel energized and alert because of cortisol. At least that’s supposed to happen if you have proper circadian rhythms.
Taking coffee will only mask the symptoms of fatigue which cover much more deeper issues related to sleep and circadian rhythms. As I said, coffee is also a circadian signaller that offsets the liver’s circadian clock. So, I’d say it’s a good idea to postpone your first cup of coffee a few hours after waking up as to allow your digestion to rest and induce deeper cellular autophagy. Coffee stimulates autophagy to a certain extent but only in small amounts and not all the time. That’s why the mid-noon small coffee break can be a good way to promote autophagy as well as give some energy until the evening.
Other circadian rhythm factors related to eating have to do with the type of food you eat as well. Some nutrients like tryptophan and serotonin can actually make you sleep better and promote relaxation. Both carbohydrates and protein specifically have these nutrients and they’re great for dinner. Getting some protein before going to bed can also be good for providing enough amino acids for your muscles and neurotransmitters.
Generally, most people find it easier and more convenient to skip breakfast and eat later in the day. I’d say it’s better for the circadian rhythms as well and not eat anything at least until noon.
In conclusion, light is more important of a circadian signaller than food but you definitely don’t want to eat a lot of food right before going to bed. The optimal time frame to stop eating for the night is 2-4 hours. Having food right in the morning isn’t ideal either and you’d like to postpone your fast by at least a few hours after waking up.
It doesn’t matter what kind of a fasting window you follow as long as you avoid eating immediately after opening your eyes, having dinner too late, and snacking all the way up to going to bed.
Chapter XXII
Sleep Optimization
“There is a time for many words, and there is also a time for sleep.”
Homer, The Odyssey
This book is primarily about fasting because it provides many health and longevity-boosting benefits without having to do anything. It’s simple – you just stop eating for a period of time, then you lift, and then you eat. However, as we found out in the last chapter, the circadian rhythms play an enormous role in how your body is going to respond to these actions.
Circadian rhythms and energy homeostasis are central to Metabolic Autophagy because they govern most of the proclaimed benefits of fasting, such as increased growth hormone, cellular autophagy, mitochondrial functioning, and insulin sensitivity. That’s why sleep is crucial for healthy living and longevity.
Sleep is probably the biggest thing that gets neglected when it comes to enhancing our performance. Lack of sleep can increase our risk of heart disease, diabetes, neurodegenerative disease, and obesity. It will also cause insulin resistance, mood swings, low testosterone, and fatigue, both physical and mental.
Human growth hormone actually gets released during the first hours of our sleep, which is incredibly important for building tissue and maintaining leanness. That 2000% boost everyone’s talking about starts at 11 PM and lasts until about 2 AM, during which the body conducts its physical repair. Missing out on this makes you gain weight and lose strength. With a circadian mismatch, you may not be even getting said benefit of growth hormone secretion or autophagy.
Figure 101 Circadian Rhythms of Human Growth Hormone
Sleep deprivation releases cortisol, which is the catabolic stress hormone. This will promote tissue breakdown and the accumulation of fat. That’s why stressed out people tend to struggle with weight loss – chronically elevated levels of cortisol from not sleeping enough, over-caffeinating, long working hours, and emotional turmoil. It’s one of the biggest things that accelerates aging and wrinkled skin. If you want to live longer and become high-performance, then you not only have to learn how to manage your stress but also get enough shut-eye.
Why Do We Sleep
Sleep is quite a paradoxical phenomenon from the perspective of evolution. Although it has many restorative benefits on the body, it’s still a gambit. In nature, while your sleeping, you’re putting yourself in risk of being eaten, getting killed, or missing out on some feeding opportunities. The fact that virtually all animals have some sort of a sleep-wakefulness cycle shows how important it must’ve been for organisms to develop this process. During sleep, the brain doesn’t actually turn off but undergoes many neurological processes.
There are 2 main types of sleep with characteristic brain wave patterns and activities.
Non-rapid-eye-movement (NREM) sleep is anything that is not REM or rapid-eye-movement sleep. It consists of 3 separate stages. The first is NREM1 between drowsy wakefulness and sleep, in which your muscles are still quite active, you’re rolling around in bed and you may occasionally open your eyes.
In NREM2 your muscle activity keeps decreasing and you start to slowly fade away into sleep.
Stage 3 NREM3 (previously 3 and 4) is the deep or slow-wave sleep (SWS) characterized by delta brain waves of 0.5-4 Hz. In here, you are cut off from the conscious world around you and irresponsive to most sounds or other stimuli.
Rapid-eye-movement (REM) sleep is a phase characterized by random movement of the eyes, low muscle tone and the possibility of lucid dreaming. It allows us to learn complex tasks and motor skills. This is where the magic happens.
One cycle of REM usually takes about 70-90 minutes depending on the length of overall NREM sleep and comprises 20-25% of total night’s volume. Light NREM1-2 takes about 50-60% and deep sleep NREM3 comprises up to 10-25%.
Figure 102 Sleep Stages
Physically, the most restorative stages are deep sleep and REM, which is why they should be prioritized much more. However, consistently over 25% of REM sleep may cause hyper brain activity, mood disorders and other neurological issues.
It’s a very good idea to use some sort of a sleep tracker so you’d have actual data about your progress. The best non-bluetooth device out there is the OURA ring that can be kept in airplane mode. It also measures heart rate variability (HRV), body temperature, how fast you fall asleep, your physical activity, and how many times you wake up during the night. You can use the code SIIMLAND to get a $50 discount at www.ouraring.com.
How much Sleep Do We Need?
The optimal length of sleep varies between people and it’s determined by genetics, lifestyle factors, circadian rhythms, and how much physical repair is needed. It’s recommended that children should get about 10-12 hours a day and adults 7-9. Too much sleep, however, can also have negative side-effects, such as insomnia, restlessness, epilepsy, obesity, and other medical conditions.
But it’s not the quantity of sleep that matters but the quality of it. Recovery takes place only in the deepest stages which we can enter after about 90 minutes. Sleeping more won’t increase our performance. Doing it smarter will. Here’s how:
Adjust to the Circadian Rhythm – The most productive hours of sleep are in the early parts of the night. As you recall, growth hormone starts rising at 11 PM and reaches its peak at 2 AM. That’s when melatonin should increase as well. Cortisol would also naturally start rising early in the morning between 5-8 AM. For optimal circadian rhythms, you’d want to stick to that as much as possible. This means: get up early at about 6-8 AM
go to bed between 9 and 11 PM
Establish a Daily Sleep Routine - Follow a series of habitual activities prior going to bed letting your unconscious self know that it’s time to go to sleep. This will include certain activities both physical and mental. It can be anything, such as reading, brushing your teeth, stretching or whatever. Just make it a habit so that your mind knows it’s time to rest. If you can’t make it to bed at the optimal hours, then you should at least focus on sticking to a consistent bedtime and waking up schedule because it’s critical for maintaining consistency with your circadian rhythm.
Sleep in Pitch Black Darkness – Blue light in the evening is brutal for disrupting the circadian rhythms and interfering with melatonin production. That’s why a pair of quality blue blocking glasses is essential but you also want to use blackout curtains and wear a sleeping mask.
Change Your Lightbulbs - The UV light from ordinary lightbulbs emanates blue light. Changing to amber lights will fix that by reducing the spectrum to more red which at night resembles the sunset.
Use a program on your computer called F.lux which changes the bright color of the screen to orange and relaxing.
Use an Acupuncture Mattress - Get a small bedding that has little spikes on top of it. This is relatively cheap yet very effective. You can lay down before going to bed for 15 minutes or sleep on it throughout the night. I have used both options. At first, it feels like a lot of thorns are trying to penetrate your skin. After a while, the body relaxes and it becomes incredibly soothing.
Sleep in a Cool Environment - The perfect temperature is 20 degrees Celsius (65 Fahrenheit). Turn down the heating and cover yourself with only the bed sheets. Extra fluffy blankets are actually counterproductive.
Turn Off All Electronics in Your Room - Not only are they a possible source of blue light sneaking in but they also radiate Electro Magnetic Frequencies (EMF) which not only decrease testosterone production but also have a negative impact on our overall health including sleep. Turn off your router for the night and keep your phone on airplane mode most of the time.
Create White Noise in Your Room - Whether that would be from an audio player switched to airplane mode or something less technical. I would suggest using a simple fan. Not only will the ventilation keep the air moving and cooling the temperature but the noise will contribute to the production of alpha waves while we are sleeping. White noise promotes a meditative state which will allow us to enter the deepest stages of recovery more easily.
Dehydrate a Few Hours Prior to Bedtime – If you have to constantly wake up to go to the bathroom at night then it’s going to interfere with getting into deep sleep. After dinner don’t consume any form of liquid as it will inevitably have to come out.
Binaural Beats - While awake our brain is producing mainly beta waves which is an alert state of consciousness that promotes stress and anxiety. To enter deeper stages, we have to drop lower into alpha waves. During the day it can happen while we’re daydreaming or meditating. Binaural beats can help us to go from beta to alpha and then progress further into theta and delta, which resembles the natu
ral progression of a healthy cycle.
Essential Oils that emanate different aromas can be used around your bed that will improve the quality of our sleep. For instance, rose oil inhibits sympathetic nervous system activity and decreases adrenaline. Additionally, lavender enhances deep sleep, lowers our stress, blood pressure, heart rate, skin temperature, and cortisol levels. Their soothing smells will prime our body and mind for relaxation and augmentation.
You should also avoid using too much coffee. Caffeine has a half-life of 6-8 hours. To not be too alert before bedtime don’t consume caffeine after 3-4 PM. It’s best to drink it in the morning or at least not later than the afternoon. Green tea has some caffeine in it but in very small doses.
A good night’s sleep starts the moment we wake up the day before. If we’re not in tune with the circadian rhythms and not follow the activities described above, then we are not getting the most out of our downtime. Our ritual prior going to bed determines how well we’re going to be resting. Sleep hygiene is very important and we need to prepare for it in advance.
Our modern world is constantly stimulating us and keeping us in the circuit. Social media, TV and working cause more stress and maintain our wakefulness. If we don’t give our body to adjust to the change then we will go to bed all wired up thus impairing our recovery. In the evening we should be winding down and relaxing. If we’re constantly wired up, we won’t be able to shut down completely. When it’s night time you have to behave accordingly. You shouldn’t be running from predators or chasing prey but instead simply take it easy and soothe your mind.