Circadian Clocks in Every Human Cell BATON Diet Blog 5
Circadian Clocks in Every Cell
Principle 1: Eat Right for Your Circadian Type
BATON Diet Blog 5
We now know that our body has clocks in every cell, and they are networked to our master clock in our brain. Over half the genes identified in the human genome are clock rhythm genes. There is evidence for genome-wide regulation of the master clock via chromosomes. Studies have begun to find the brain clock’s influence in controlling gut biome, heart function, the nervous system, cancer, and aging. (2026)
Body clocks are not total slaves to our master brain clock.
Our body clocks are networked to our brain master clock, but they are not total slaves to our master clock. Body clocks (local clocks) receive other timing inputs and cues as well as being connected to our master clock.
Liver clocks are more sensitive to the timing of when we eat than they are to light.
Lung local clocks respond to differing levels of oxygen in the atmosphere at different times of the day. However, all our clocks remain networked to the brain master clock. A circadian clock protein in lung cells prevents cystic fibrosis. Mutation of the lung clock protein allows cystic fibrosis to develop and is identified with abnormally short sleep times in people who have cystic fibrosis. Circadian risk factors for pulmonary fibrosis are shift work and short sleep. (2050)
The gut-brain connection is influenced by body clocks (local clocks) in the gut that control the timing of production of hormones that travel from the gut to the brain. Two such hormones are melatonin, the sleep hormone, and serotonin the mood lifting “happy hormone” that are produced in the gut and then travel to the brain to exert their effects. There appears to be truth to the saying “I have a gut feeling” regarding decision making.
Our liver, stomach, pancreas, and intestine clocks are not entirely slaves to our master brain clock. They respond more to when we eat than to light. They want to be coordinated with our master brain clock which responds more to light. If we eat at the wrong time it disturbs our circadian rhythm influencing metabolism, physical coordination in sports, and workplace safety.
Disruption of pancreas circadian clocks resulted in low insulin levels and diabetes in animals. Marcheva B et al, 2010, Nature (1951)
Image by Davide Gnocchi et al, Adjusted CC (2034).
Body clocks synchronized with the brain master clock orchestrate health.
Studies indicate that when our body clocks are in disharmony with our brain master clock, for example in people who are shift workers, then accidents, injury, and disease risk increase.
Drivers have more accidents during the periods when we switch to and from daylight savings time. When our body clocks are in synchrony with the master clock in our brain, they direct the symphony of health and safety. Image “Shifting rhythms” by Oregon State University, Adjusted, CC (2043)
Exciting fresh approach in nutrition research
Eating to support circadian rhythm via time centered eating (eating right for your circadian type) is a fresh and exciting approach in nutrition research. Since Gill and Panda published their stunning results in the first big study in humans in 2015, this field has become vast and rich. The Nobel Prize in Physiology and Medicine 2017 was awarded to Jeffrey C Hall, Michael Rosbash, and Michael W. Young for their discovery of what makes our master clock perpetual in motion and yet so elegantly designed that it can be reset if we move to another time zone.
Rapid growth in a rich and vast field
In 2017 there were only 2 to 3 human trials in the literature on time centered eating. Since 2017 the literature of human studies has grown rapidly, and we now have over 50 good clinical studies of circadian time restricted eating (TRE) in humans with more being published regularly.
The studies in humans vary from athletes undergoing training, to the elderly, people with prediabetes, fatty liver disease, obesity, people on home IV nutrition, healthy people, and shift workers including our first responders like firemen. A good selection of studies is in women as well as men, small studies, and large studies have been published. Supporting our internal brain master clock and our body clocks plus removing disruptors of circadian rhythm is now being proposed as part of healthy lifestyle and healing.
Eating to support circadian rhythm is now being proposed as part of healthy lifestyle and healing.
What is the difference between circadian time centered eating and intermittent fasting?
Before we go further, it is good to define what we mean by eating to support circadian rhythm also known as time centered eating or time restricted eating (TRE) versus intermittent fasting.
Intermittent Fasting Circadian time centered eating
Calories are limited No limits on food intake or calories
Fasting frequency varies Daily practice at the same time of day
Eating time window changes Consistent time window for eating daily
Not designed or intended Purpose is to support circadian rhythm
to support circadian rhythm
Example 5:2 or 1:1 or 30:1 Example: 10:14 or 8:16
CALORIE INTAKE
Intermittent fasting almost always involves calorie restriction.
Circadian time centered eating places no restrictions on foods or calories.
TIMING OPTIONS
Intermittent fasting typically has variable food intake periods. Thus, the time interval varies considerably in intermittent fasting, and while it can have health benefits, it does not support circadian rhythm. Some examples of intermittent fasting are to restrict calories for 2 days and then eat normal intake for 5 days a week (5:2 ratio). Or intermittent fasting may be done every other day with reduced and normal food intake (1:1 ratio). Another intermittent fasting timing option is a person may choose a program to fast 1 day per month (30:1), or once per year for a longer fast of 3 days (362:3).
Circadian time centered eating (eating right for your circadian type) is also known as TRE (time restricted eating). It occurs at the same time each day typically during daylight hours. Our circadian rhythm is consistent and anticipatory, so eating during the same time window each day helps to synchronize the circadian system and allows it to anticipate and prepare the body for processing food. One example of circadian time restricted eating (TRE) is 10:14, eating during a 10-hour window and water only fasting for 14 hours. Each person chooses their own 10-hour eating window during daylight hours. One person might select to start eating at 9am and stop eating at 7pm and another person might choose to start eating at 8am and stop eating at 6pm. Another example of a circadian time centered eating schedule is 8:16, where a person eats in an 8-hour window during daylight hours followed by water only fasting for 16 hours.
DESIGN AND INTENTION
Intermittent fasting is not designed or intended to support circadian rhythm. Intermittent fasting, like traditional fasting has been shown to have health benefits, but it is not engaged in design to improve circadian rhythm.
Eating right for your circadian type (circadian time centered eating) (TRE time restricted eating) is a way of giving the body strong consistent cues at the same time each day to train our body to know that at this time of day we will eat. This way the body knows when food will be coming and can prepare hormonally in advance to digest food.
Which rhythms are circadian rhythms?
A circadian rhythm is any rhythm that occurs about every 24 hours in the body. For example, our sleep/wake rhythm is circadian because it occurs every 24 hours. Our circadian rhythm influences our behavior, metabolism, weight, health, wellbeing, and safety.
This illustration shows some of our behavior and metabolic functions that are circadian.
What inspired researchers to study if when we eat is important?
An intriguing finding in animal studies at Panda Labs of the Salk Institute sparked scientists to search to find out if humans reacted the same way. Mice are nocturnal 
and they eat during the night when they are awake. When mice were fed a standard mouse chow, the mice ate at night and remained healthy. Mouse chow is low fat chow.
High fat chow
However, mice fed high fat chow gained weight. No surprise here, there are over 11,000 published studies validating this model to induce obesity.
Cool observation
What these astute researchers noticed was that not only did the mice fed a high fat diet gain weight, but they also changed the time they were eating. Instead of eating just at night when they were awake, they started snacking during the day and night around the clock. The mice gained weight and they lost muscle and endurance and became more sedentary. (2091)
High fat 12-hour feeding
Next, the research team decided to see what would happen if mice were fed the same high fat diet with the same number of calories but were only allowed to eat during 12 hours at night when they would normally eat. (2091)
Good News!
Even though both groups of mice were fed the exact same number of high fat calories, ...
The mice that ate only 12 hours at night, when they would normally eat, gained 70% less body fat.
They weighed 28% less than mice that were fed the same high fat diet with the same number of calories but allowed to eat whenever they wanted to.
The 12-hour fed mice maintained most of their endurance in treadmill tests.
The 12 hour fed mice had completely healthy livers. (2091)
Health benefits of circadian time centered feeding seen in animal studies
After the first mouse study many similar studies were done in animals. The studies consistently reported health benefits shown below.
Adapted from Panda, Satchidananda. “Circadian Physiology of Metabolism.” Science, 2016. Vol 354, no. 6315 pages 1008-1015. (2247)
But would circadian time centered eating help people like it did animals?
The Gill and Panda study of 156 people “living in the wild”
The above experiments were very exciting, but would the same thing happen in humans? These results inspired the Gill and Panda study, the first large study of 156 people.
Please see BATON Diet Blog 6
We will present the exciting results of the first large study in humans of Circadian Eating by Gill and Panda.
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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.