What is Intermittent Fasting?
Intermittent Fasting, also known as Time Restricted Eating, refers to when eating is limited to a certain number of hours each day, preferably within an 8 to 12-hour window. Intermittent fasting is getting a lot of buzz these days for all the health and weight loss benefits that people are receiving. One of the foremost intermittent fasting researchers is Dr. Satchin Panda of the Salk Institute. These are the key takeaways from Dr. Rangan Chatterjee’s Podcast with Dr. Satchin Panda Feel Better Live More Episode 81
Circadian Rhythm
Circadian Rhythms are daily cycles in sleep, work, eating, fasting and our ability to do exercise/physical activities. All the rhythms that we experience on a daily basis.
The reason why we have these rhythms is because these are controlled by circadian clocks that are present in almost every organ, every cell and every part of your brain.
If you are locked inside a room with access to food and bed but no clue about timing, the circadian clocks inside our body will produce rhythms so that you will go to bed at 9pm every night and wake up around 6/7 in the morning. This will continue even without access to timing cue. (But light and timing your light exposure is very important to keeping these rhythms running optimally for your health and wellness, read more on the importance of light exposure from our blog by clicking here)
The most obvious circadian rhythm is the daily Sleep-Wake cycle.
But that’s just the tip of the iceberg and there are many others rhythms that go on inside our body.
What does intermittent fasting do to your body?
Many genes that are involved in absorbing nutrients, breaking them down, metabolizing them, and supplying nourishment for our body, go through daily circadian rhythms. That means a certain time of the day or night, our body may be much better in handling a big meal or breaking down toxins than other times of the day.
Dr. Panda tested if our liver and our gut is better primed to digest and use these nutrients at certain times. Is it better if we align eating time to that time?
Epidemiology of Chronic Diseases
If nutrition quality has a large impact on disease, then we would have seen that certain countries and cultures that eat a more refined carbohydrate diet, high fat diet, would have had high proportion of these chronic metabolic diseases. But they don’t.
Cultures in the past didn’t suffer from chronic metabolic diseases, even though they didn’t have the healthiest diets. One reason for this was people had very little access to food at night because staying up at night under light was expensive even in the middle of the 19th century. It will take almost half a month of salary of the average income family in the UK to buy enough fuel to light up the home for 3-4 hours in the evening. So the last time people would eat is during day time, and very little consumed after evening.
Digestion Process At Night
The very first step is that saliva production slows down, the second step is as the food hits the stomach, the stomach produces various digestive juices, including stomach acid.
In the evening the stomach produces excessive acid as a defense mechanism because we are not likely to eat anything in the evening. So if something goes into the stomach at night, it’s likely to be pathogenic bacteria.
As our brain sleeps, our digestion also slows down, so the intestine doesn’t pump food down the digestive tract at night.
The reason why the digestive process slows down at night is that, throughout the day, digestion and moving the food to our digestive tract causes a lot of damage to the stomach/intestinal lining and that has to be repaired.
Almost 1/10th of our stomach lining is repaired and replaced every night and it’s like not being able to repair a highway when there are cars and trucks moving, we can’t repair our gut if we eat at night.
“The circadian clock in our gut slows down (the digestion) process so that it can repair the gut lining that causes various gut problems, inflammation, which can lead to developing allergies to some of the food that we eat.” – Dr. Satchin Panda
The biggest factor that has the most influence on our circadian rhythm is light
The weather can be different each day but almost in every day there is one thing that is going to happen. The sun will rise up and the sun will set in the evening and there will be darkness.
In the modern society we have access to light 24/7. That confuses our brain clock.
After sunset, the brain clock will anticipate 1-2 hours of twilight time, but beyond that when it sees light it disrupts your circadian timing, making your body think that it isn’t night time. This can lead to a disruption or reduction to our sleep.
Sleep Deprivation and Eating
As we know now from sleep research, a sleep deprived brain can’t make the right decisions.
This is an issue when we make hundreds of decisions throughout our day with what to eat, how to eat and when to eat, or what combination of food to eat.
“We just completed a study where we found that nearly 80% of our genes rise up and fall down or have a circadian rhythm in different parts of the organs. That also implies that nearly 80% of the drugs that target different genes should have a peak performance time and peak time for adverse effect” – Dr. Satchin Panda
Which Intermittent Fasting App is Best?
Dr. Panda wanted to see was if My Circadian Clock App users maintain the habit of Time Restricted Eating. Surprisingly they maintained it, and they stuck with the diet pattern because they felt more energetic throughout the day, they slept much better and they didn’t have acid reflux or heartburn. They realized what affects us is a good night of sleep, feeling more energetic throughout the day and not having the heartburn or stomach pain at night.
Using the app Dr. Panda was able to conduct larger study with tens of thousands of people from all over the world, sharing their data and learning about what diseases time restricted eating within 10 hours would help. He also found that some people can even go down to 8 hours, and some over 11-12 hours, but any interval from 8-12 hours is good enough if people can stick to it.
The ethics committee has approved the app to capture data from anywhere in the world long as they have a smartphone that runs on apple iOS or Android device and has a camera option so they can share their data. There are a lot of apps out there but they capture data for commercial purposes, but with My Circadian Clock, all the data captured is de-identified, anonymized and is put in HIPAA compliant software with the latest privacy rules and data aren’t shared with any outside entity.
“There are nearly more than 100 diseases where just taking care of your daily rhythms by paying attention to when people eat, when people sleep, how much they sleep, will substantially and significantly reduce the disease risk.” – Dr. Satchin Panda
What is the Best Timing for Intermittent Fasting?
This goes back to people’s lifestyle. For example some people go to bed late because of their work or family issues, then they wake up very late in the morning (8-9am). For them we can’t come back with a simple universal rule that one should eat breakfast at 6/7am.
When we wake up, give yourself at least an hour before you have your first cup of tea, coffee or breakfast. Another reason why it’s important is as we wake up, sometimes we wake up to an alarm clock, so although our body tends to wake up, many of our hormones that keeps us asleep haven’t gone back to the waking state.
10 hours is a good starting eating window, because some people get stuck in traffic or you may have to come home and prepare food. So even if you go to 11 hours you are not booted off time restricted eating. You will get a lot of the benefits anywhere between 8-12 hours.
Time restricted eating can also be a solution to help your family be in sync. With 10 to 12-hour time restricted eating, everyone from a 5-8 year-old or an 80 year-old that are living at the same house can follow the practice. When the eating time is synchronized, it also brings back family time together. This is a way of life that is beyond trying to improve your personal health but also improves your family’s health.
I personally recommend people to try to put their eating window from 10 AM to 6 PM or 12 PM to 6 PM. I prefer and believe myself that you gain more health benefits when you have a shorter window of 6 to 8 hours. I think it is very beneficial to stop eating around 6 PM (if you can), this will be very good for your digestive system’s ability to repair, as you leave several hours between your last meal before you go to bed. (Ideally getting to bed by 10-11 PM)
Can You Drink Coffee or Other Fluids When Intermittent Fasting?
Yes, the time restricted window includes all food and drinks (not including water). It is advised to limit coffee to that window for two reasons:
1. When you need coffee when you just got out of bed, that’s a warning sign that you are not getting enough sleep.
2. Your insulin response tends to be low because melatonin may still be high in the morning.
When you really need that coffee or tea, you can try without milk or sugar because that will reduce the chance of your pancreas waking up. (There are different intermittent fasting methods, Dave Aspery is a big proponent of this bullet proof coffee in fasting, more info on this in a blog update soon to come)
Usually our body clears half of the caffeine within 6-7 hours, so if we have coffee at noon, half of the caffeine is still in our system by 6-7 pm. That’s one of the reasons why people can’t go to sleep if they have coffee or tea in the afternoon.
How to Boost your Growth Hormone with Sleep
Almost every hormone has a circadian rhythm. Growth hormone goes up in the first half of our sleep, it also goes up when we have an empty stomach before sleep. Going to bed early has a huge benefit on growth hormone release. People past their 20s are not growing, but growth hormone helps to repair their body.
Most people have to wake up around 7-7:30am. So if you go to bed past midnight, you are reducing the number of hours of sleep. It has been shown in a number of studies that people who go to bed later get less sleep. So when they get less sleep, they get less growth hormone.
Intermittent Fasting and Shift-Workers
Shift-work is very challenging, it takes a huge toll on their body because when they should be asleep, they are awake working.
Dr. Satchin Panda has a current study on firefighters (150 San Diego Firefighters) because they have a 24-hour shift. On for 24 and off for 24. It goes for 4 cycles and then they get 4 days of off. What we are trying to figure out is can they do time restricted eating at least on their off days to build up resilience, vitality and repair capacity. So when they do this grueling shift work, it doesn’t have lasting adverse impact on the body. Can they stick to eating within 10-12 hours during their work days in a way that is aligned to their work schedule.
Dr. Panda gave them tips on how to sleep well during off days or day time when they have the opportunity to sleep. Many of them found it easy to adapt. He we will monitor the firefighters for 1 year. They are hooked up with continuous glucose monitors so he’ll see meal by meal and depending on the stress levels, how many emergency calls they are taking, how their body is responding in terms of glucose.
If you are interested in learning more about your circadian rhythm and time restricted eating, check out Dr. Satchin Panda’s Book called The Circadian Code.
Resources:
- Link to Satchin’s paper on how time restricted feeding can prevent some chronic disease
- Vogue.com – The Healthy Diet of the Future Focuses on When—Not Just What—You Eat
- Dr. Panda’s Instagram & Twitter
*This blog is being updated with more info and current research on intermittent fasting and time restricted eating. More to come with info from Dr. Valter Longo, Dave Aspery and Dr. Jason Fung.
