Every year daylight savings time causes a week of agony for many of us. We feel less rested, more irritable, and very blah (for lack of better words). Some people suggest preparing for the time change weeks in advance while others propose adapting other areas of your life to help you adjust. One of the more common suggestions is using your meal times to try and “hack” into the circadian rhythm and reset the clocks a little faster. In this article, we will explain what the circadian rhythm is and its major influences. Then we will look at whether or not meal timing has a real effect on it. Keep reading to answer the question: Can meal timing improve your sleep?
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Overview of the Circadian Rhythm
Our bodies operate on cycles. We have positive and negative feedback loops occurring throughout the day, our cells recycle themselves on a regular basis, and our hormones fluctuate in a cyclical manner on a 24hr cycle and additionally on a monthly cycle for women.
The circadian rhythm is a natural cycle that is controlled by our biological clocks (yes, we actually have these). We have a master clock in our brains known as the suprachiasmatic nuclei (kī-ăz-măt′ĭk), which is controlled by the light signals (the sun, mainly). We also have peripheral clocks. These are things like neural pathways, hormone rhythms, body temperature signals (thermoreceptors), and finally signals from feasting and fasting cycles.
The core hormones involved in the peripheral clock-system are cortisol, ghrelin, insulin, leptin, and melatonin. Cortisol acts as a messenger between the master clock and the peripheral clocks and is a powerful hormone. Primarily it triggers a number of other hormones and functions in the body that control our stress response (fight or flight) and can additionally be used to help wake up the body. This is why it is recommended to drink water at the beginning of your day instead of coffee as your body is naturally producing cortisol to help wake you up. If you want to have a coffee, wait at least an hour after you’ve woken up before you have your first cup.
As part of the cascading effects of cortisol, your body will eventually send signals to your brain telling you that you are hungry. This is triggered by ghrelin. If you want to remember, think of your stomach grumbling – that’s caused by ghrelin.
So you feel your stomach grumble, and you decide to have some breakfast. Depending on the breakfast you eat you’ll trigger insulin to be released. This is a hormone that originates in the pancreas and acts as a doorway to the cells of the liver, muscles, and fat cells to allow glucose (sugar molecules) into the cells. To remember this hormone, think about how insulin lets glucose into the cells. The cells then use this for energy production. If not used, they will be stored for later use in adipocytes, or fat cells.
After a few bites of breakfast, you start to feel satisfied and full. This is triggered by the hormone leptin. If you want a way to remember this hormone, think about leftovers. Leptin causes you to feel full and might create leftovers. Or you can just remember that this is the opposite of ghrelin.
After your first meal of the day your body will go through a series of cycles of ghrelin, insulin, and leptin until the sun starts to go down or your final meal of the day. The change in light and that final release of leptin will trigger the master clock to start the production of melatonin. This is the hormone that will make you feel mellow and will eventually help your brain prepare for sleep.
So now that you understand the basics of the circadian rhythm, let’s look at how you can strategically time your meals to have a better, more restful sleep.
Meal Timing for a Better Sleep
As we mentioned before, the master clock is mainly controlled by lights signals, and the circadian rhythm is controlled by both the master clock and peripheral clocks. The peripheral clocks we will be focusing on are the hormonal signals and how they relate to the fasting and feasting signals.
We cannot control when the sun comes up or goes down, so controlling the master clock can be tricky (although happy lights, blackout blinds and blue-light filters can help). So we have to look at what we can control and that’s our mealtimes.
The idea behind meal timing and improving your sleep is that if you prolong your fasting phase in the morning and give yourself enough time between your final meal and your desired bedtime this will improve your overall sleep quality.
Most people are not that hungry in the morning, so if you prolong your fast you have a chance to eat a more substantial meal later in the day. This could be beneficial for your insulin levels as well, depending on what you choose for your first meal.
Later in the day, if you have dinner at 7 pm and want to be asleep by 10 pm, this (theoretically) will give your body 3 hours to prepare for sleep and start producing more melatonin.
Related Article: Fast Facts on Intermittent Fasting
But does this really work?
The Power of the Sun
According to a study published in Current Biology on Meal Timing Regulates the Human Circadian System, meal timing won’t affect your sleep. In fact, they studied the levels of melatonin (sleep) and cortisol (wake-up boost) in participants when they ate at 30 minutes after sunrise and had their final meal 10.5hrs later and then again when they ate breakfast at 5 hours after sunrise and their final meal at 10.5hrs later. Both groups had a rise in melatonin starting at 11 pm (1 hour after dark) a peak at 3 am, where it then began to decrease. Cortisol-levels started to increase at 3 am and peaked at around 8:30 am (1.5hrs after sunrise), with a secondary bump at around 3 pm.
So it looks like meal timing may not have the effect on our sleep cycles that we originally thought. *Keep in mind that this study was done on 17 healthy young men in a controlled environment.
The constant between the two meal timing routines was the simulation of light and dark that the participants were exposed to. “Night” was simulated between 10:00 pm and 7 am. The day was simulated between 7 am and 10:00 pm. As soon as it was dark, the participants started to produce melatonin and as the melatonin started to decrease after 3 am (or 5hrs after the dark phase started) the cortisol began its steady incline, preparing the body to wake-up.
If You Want to Get a Better Sleep, Try This
So now that we know how powerful the light signals are for our circadian rhythm, here are some actual ways to improve your quality of sleep:
- Get black-out blinds for your bedroom or an eye mask. Complete darkness is best for a good, uninterrupted sleep
- Use blue light filters on phones and other devices to limit blue-light exposure after sunset: The brain doesn’t know the difference between sunlight and the blue light emitted from technology. So if you want to help the body produce melatonin at night, make sure you set the blue light filters to turn on at sunset.
- Reduce food intake after sunset: if you eat this will signal all of those other periphery clocks to let your master clock know it is not time for bed yet. This will interrupt the production of melatonin, and result in less restful sleep. Both meal timing routines had similar melatonin and cortisol cycles because the participants didn’t eat after dark
One Final Fact from the Study
One of the interesting observations from the study was that when the participants waited 5 hours before their first meal, their blood sugar levels were lower. This could mean that extending your fast after waking up could be beneficial for blood sugar levels, which is a good indicator of metabolic health.
Sleep is a crucial part of our lives. We need it to rest, recover and prepare for the next day. Although food timing may not have the greatest impact on our circadian rhythm, we can say that eating after dark is not great for a restful sleep and that extending your fast in the morning can lead to lower blood glucose levels.
