Circadian Rhythm

Circadian rhythms are very important in mammals. There are many clocks in your brain and body, but they are all controlled by the master clock, the suprachiasmatic nucleus (SCN). Circadian rhythms and clocks, the SCN, and what affects them is only recently starting to be understood. The findings so far are fascinating.


Light plays a big role in regulating your circadian rhythms. Humans evolved with activity governed by nature, which means our exposure to light. The brain starts to boot up with its first exposure to bright light, and begins its shutdown sequence around 12 hours later, when the human body assumes is nighttime, and dark. Many other internal clocks are tied to this system and gene expression with them.


The timing of meals is another big factor in circadian rhythms. Again, looking at early humans explains why. At the end of the day the body will shift hormone production in preparation for sleep. Basically, the body will switch modes, from active to rest. Digestion will slow, metabolism slows, etc. At the same time, melatonin increases, which aids in sleep quality. So following a time-restricted eating (TRE) schedule will benefit your energy levels, fat loss, lean mass, sleep quality, and more.


It’s not all bad. There are things you can do to stay in rhythm, so to speak. As far as light goes, try to dim all lights, screens, etc. as you near bedtime. If you can get LED lights that can be set to specific colors: harsher, cooler (i.e. bright blues) colors in the beginning of the day, and warmer, dimmer (i.e. reds/oranges) as the day becomes night. As for timing your meals, TRE is relatively easy to do. TRE is not the same as intermittent fasting. With TRE, you basically follow the natural flow of the day. After waking up, once you have your first meal, about 12 hours later, should be your last meal. This should line up so that you’re eating an hour or two after waking and before going to bed.


This is a very dense topic, so this post barely skimmed the surface. Here are some good places to read more:



Author: NFShealth

Certified personal trainer, grad student in nutrition. Obsessed about all things regarding nutrition and health.

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