Chronobiology - The Study of Sleep

Biological rhythms have shaped our lives since the dawn of time. Your internal or circadian rhythm is basically a 24-hour clock that is running in the background of your brain and cycles between sleepiness and alertness at regular intervals.

What is Chronobiology?

Biological rhythms have shaped our lives since the dawn of time. Your internal or circadian rhythm is basically a 24-hour clock that is running in the background of your brain and cycles between sleepiness and alertness at regular intervals.

Circadian rhythms are physical, mental, and behavioral changes that follow a daily cycle. They respond primarily to light and darkness in an organism's environment. Sleeping at night and being awake during the day is an example of a light-related circadian rhythm. Circadian rhythms are found in most living things, including animals, plants, and many tiny microbes. The study of circadian rhythms is called chronobiology.

What are biological clocks?

Biological clocks are an organism’s innate timing device. They’re composed of specific proteins that interact in cells throughout the body. Biological clocks are found in nearly every tissue and organ. Researchers have identified similar genes in people, fruit flies, mice, fungi, and several other organisms that are responsible for making the clock’s components. Biological clocks produce circadian rhythms and regulate their timing.

A master clock in the brain coordinates all the biological clocks in a living thing, keeping the clocks in sync. In vertebrate animals, including humans, the master clock is a group of about 20,000 nerve cells that form a structure called the Suprachiasmatic Nucleus, or SCN. The SCN is located in a part of the brain called the hypothalamus and receives direct input from the eyes.

Does the body make and keep its own circadian rhythms?

Natural factors (such as cortisol levels) within the body produce circadian rhythms. However, signals from the environment also affect them. The main cue influencing circadian rhythms is daylight. This light can turn on or turn off genes that control the molecular structure of biological clocks. Changing the light-dark cycles can speed up, slow down, or reset biological clocks as well as circadian rhythms.

Do circadian rhythms affect body function and health?

Yes. Circadian rhythms can influence sleep-wake cycles, hormone release, eating habits and digestion, body temperature, and other important bodily functions. Biological clocks that run fast or slow can result in disrupted or abnormal circadian rhythms. Irregular rhythms have been linked to various chronic health conditions, such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.

Aligning our periods of activity (and inactivity) with our individual circadian rhythms is an essential step in wellness optimisation. Understanding these intrinsic patterns can help us plan our daily routine to align with these patterns.

You may already have insight into the times of the day that you are most productive or have the most energy. Take a moment to consider some of these various daily activities and states:

Chronobiology and Cognition

A sharp and switched on mind is when you will get your best work done. But what factors optimise this most productive part of the day?

Consider your own patterns of alertness:

  • Do you prefer early morning or late night study and focus?
  • Do you suffer from a slump in alertness after meals or mid afternoon?
  • Do you rely on caffeine to get you through that last meeting of the day?

Our underlying metabolic functioning plays a huge part in this process. In our following article series, we will explore the ways that fasting and ketogenesis can in fact sharpen our cognition, speed up our mental processing and clear away that mid-afternoon mind fog.

Chronobiology and Movement

Exercising in the morning has a fantastic effect on endorphins for the day and switches on metabolic processes for improving body composition. It’s an ideal time to exercise but its not for everyone and after the self righteousness wears off, many of us just want to crawl back into bed.

On the other hand, in the afternoon, your core body temperature is at its peak, which in turn primes skeletal muscle, allowing for better performance and an increased metabolic rate.

Often however, we must fit exercise in amongst our busy schedules as well as modifying what we do and where we do.

We will discuss some of the latest theory around movement in detail later, however at this stage, try and consider how your current exercise positively (and negatively) impacts on your daily routine and circadian rhythms.

Chronobiology and Nutrition

We have known that the body is sensitive to our diet for a long time. Recent research in chronobiology reveals that there are two dietary factors that can affect the body’s rhythm. What is eaten, combined with when foods are eaten, ultimately affect the person’s internal clock.

The body’s key organs function at their best during certain times of the day. Studies show that it is possible to train the body by eating certain meals at certain times each day, to improve the body’s digestive performance and reduce the risk of gastrointestinal issues.

When One Eats

Research supports the theory that there may be broad implications for eating at night. Some medical professionals suggest that fasting during the late night hours can be an important weight management step to take. Researchers from the Salk Institute recommend a time-restricted diet, confining eating to 8-12 hour periods (see below).

Scheduling meals earlier during the day has also proven to be a viable way to reduce chances of weight gain. Approximately 40 percent of the calories should be consumed at lunch before 3 p.m. to continue weight loss. Findings published in the International Journal of Obesity showed that people who ate lunch earlier in the day lost more weight than those who ate lunch later in the day. Additionally, those who ate lunch later in the day showed lower insulin sensitivity, which has been associated with the development of type II diabetes.

What One Eats

Your DNA and an analysis of your epigenetics will allow a highly personalised nutrition plan. Factors such as your AMY1 copy count will impact on for example the amount of carbohydrates you should be consuming.

For example:

Your last meal of the day should be at least 3 hours before bed and consist of protein rich foods such as fish, chicken or turkey, non-starchy vegetables such as asparagus, broccoli and bell peppers, with a measured amount of cellular (plant) carbohydrates such as kumara, appropriate to your own particular carbohydrate processing ability. By restricting further carbohydrates in snacks late at night before bedtime, your body will release less insulin during sleep. When there is no more glucose left in the bloodstream, your body resorts to using fat stores to fuel cellular processes.

This gives your body the rest of the evening and the whole night to break down fat stores for fuel, thereby helping the body to either maintain or decrease weight. The protein consumed is broken down into amino acids that then have the task of repairing tissues and organs, balancing the body’s pH level and maintaining the immune system.

The exact timing and make-up of your meals that will optimise your health and well-being should no longer be guesswork as we learn and understand more about your genetic profile.

Dr Brett Gerrard

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