EARLY BIRDS AND NIGHT OWLS Individuals Vary in Their Circadian Rhythm BATON Diet Blog 7

December 14, 2023

Early birds and night owls. 

 

People do vary in their circadian rhythm. But how big is the variation between individuals? 

All of us have the same quality of circadian rhythm, but some of us wake up later than others. Early bird people may wake up refreshed and pop out of bed at 4 am, while night owl people can wake up as late as 8 am. We all experience the same quality of rhythm, but we can be shifted by up to 4 hours. In medical publications early birds and night owls are called early and late chronotypes. 

 

Circadian types: individuals vary in their circadian rhythm by up to about 4 hours. 

 

Consider individual variation. Individuals vary in their circadian rhythm. The bell-shaped curve shows how 53,689 people varied by about 4 hours in their preferred mid-sleep time on their days off work. (Roenneberg, et al 2007 (2049) Circadian rhythms are genetic and based on sex. These are the reasons why most studies completed in people of circadian time centered eating allowed each person to choose their own eating window, as long as it was during daylight hours, and their eating window duration was the same length as other people in the study.

The reason for this is because insisting that all people in a study eat during the same exact time window instead of letting each person select their window negatively impacts study results. Our eating times are based on social events as well as our circadian chronotype. If people have an important social meal to eat with others, they can choose an eating window that includes the social mealtime. 

Interestingly, smoking is significantly higher in late chronotypes. (2053) 

 

In health, people fall asleep at about the same time each night. 

 

Healthy people experience only small variation in their personal circadian sleep rhythm. This is because our master circadian clock is anchored daily to the rotation time of the earth via our exposure to bright light (outdoor light in the blue and green spectrum). Being outdoors in bright sunlight for at least 30 minutes daily helps to fine-tune our circadian clock and anchors our circadian rhythm to the 24-hour day.

 

 

Do blind people have circadian rhythm? 

 

Some blind people do synchronize to light like seeing people. (2086) Even if a blind person is not able to see the visible world, they may have photosensitive retinal ganglion cells (pRGCs) of their optic nerves of the retina in their eyes that are intact. If they do, they will have normal circadian rhythm. This is because the photosensitive retinal ganglion (pRGCs) nerve cells carry the light cue messages to the SCN (suprachiasmatic nucleus) in the brain where the master clock resides. 

Blind people whose photosensitive retinal ganglion cells (pRGCs) of the optic nerves are damaged will not respond to light cues to their circadian rhythm. In a small study most totally blind people had abnormal circadian rhythm and half had free-running rhythm. (2086) However, people with this condition can synchronize by carefully timing their food intake and they may take melatonin supplement in some cases. (2087, 2088) Researchers at Yale found that optic nerve hypoplasia can result in disturbance of circadian rhythm and sleep disorders. (2047) 

 

The human circadian clock runs a little longer than 24 hours per day. 

 

If we are not exposed to bright light, our internal circadian rhythm is a little longer than 24 hours. Our internal circadian clock exceeds 24 hours by 15 to 30 minutes per 24 hours when we are not exposed to light. Exposure to outdoor bright light, especially in blue and green wavelength regions, resets our internal clock to be exactly 24 hours. 

 

 

“Free running” 

 

“Free running” is the medical term for the natural circadian rhythm shifting that occurs without light exposure. 

When we are not exposed to bright light, we become like teenagers wanting to stay up later each night and waking up later each day. Between the ages of 10 and 20 young people experience a change in their circadian rhythm that results in delayed sleep onset times. (2052) 

 

Eating window longer than 10 hours disrupts sleep and circadian rhythm. 

 

Disruption in our circadian rhythm may occur when our food intake exceeds 10 hours per day and if food intake is not in sync with our light exposure. 

 

Eating for more than 10 hours per day disturbs melatonin sleep hormone production and we start acting like the mice in the studies; we begin napping around the clock plus snacking around the clock. Interrupted sleep is not refreshing, and leaves people exhausted. 

 

Review: 

 

Muscles are repaired and built during prolonged deep night sleep. When circadian rhythm and deep sleep are disturbed, muscle mass reduces, strength wanes, and coordination is reduced. Weakness, frailty, and accidents become real risks. 

Weight gain occurs in humans and mice when they eat more than 12 hours per day. (2029, 2091) Sleeping less than 7 hours predicted future weight gain. Sleeping more than 7 hours was not associated with weight gain. (2123) 

Gut biome diversity is narrowed when we eat in a window exceeding 10 hours per day. Reduced gut biome diversity blunts gut production of serotonin the “happy hormone” and melatonin our “sleep hormone” and changes gut-brain hormone connections. 

 

 

 

The cutting-edge healthy diet of the future will focus on not only what we eat, but when we eat. 

 

What happens if I break my water fast? 

 

What happens if I just eat a very tiny snack during my water fast like: 

1/2 of a banana? or 

Cup of black coffee? or 

Cup of tea with only one teaspoon of sugar? 

 

“There’s no crying in baseball” Tom Hanks line in A League of Their Own 

 

Without even doing a study, the answer to this question comes from known physiology and biology of the body. When we eat or drink any of the above items, the entire gastrointestinal track turns back on and goes to work instead of resting and repairing the infrastructure and replacing lining of the gastrointestinal system as would normally occur during water fasting at night. If digestive organs remained at rest and did not go back to work after the snack, the blood sugar would rise too high even from a snack with the equivalent of just 1 teaspoon of sugar. 

 

 

One teaspoon of sugar is enough to raise blood sugar by 200mg/dl of blood in a person, resulting in high blood sugar. If we were to take a person and bleed them dry, remove all their blood, and then look to see how much sugar is in all the blood from their body, it would amount to less than 1 teaspoon of sugar to achieve a normal blood sugar level of 60 to 120mg/dl. 

 

There’s no snacking in the water fast of circadian time centered eating. 

 

If a snack with as little as one teaspoon of sugar is eaten, the entire digestive system must turn on to process and package the sugar for later use to prevent the blood sugar from rising too high. The stomach produces acid. The stomach breaks down the complex sugars to simple sugars. The food is then dumped into the intestines for further digestion. The pancreas produces insulin to help the sugar enter cells. The liver and gall bladder provide bile. The liver converts the extra sugars into triglyceride fats and packages them for later use, finally the triglycerides are absorbed from the intestines into the blood and delivered to the cells for storage as fats to use later for energy. Fat burning stops because fat storage takes precedence. Muscles weaken and waste away. Lack of coordination and weakness contribute to accidents and injuries at work, at home, and in sports. 

 

 

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