STEM-Talk – Dr. Satchin Panda on Circadian Rhythms and Time-Restricted Eating to Improve Health

Check out the STEM-Talk Episode Page and Show Notes

Key Takeaways

  • Black coffee in the morning does not appear to signal the start of the eating window
    • But you absolutely cannot put cream/sugar in it and still be in a fasted state
  • Mouse studies show that time-restricted eating leads to weight loss (specifically coming from a loss of body fat)
  • A sleep deprived brain tricks us into thinking we’re hungrier than we actually are, and hinders our decision making ability when it comes to food (what to eat/when to stop eating/how much to eat)
  • Sleep deprivation, in combination with late night eating, is very problematic
    • During sleep we produce growth hormone that help repair damaged cells – When we sleep less, we have less of this growth hormone present to repair our cells
    • When we eat late into the night, our stomach is thus working late into the night to digest the food – so the stomach cannot repair itself
    • Lack of growth hormone, in conjunction with food in the stomach, slows down the repair process
      • This causes damage in the gut which can accumulate
      • When the gut lining is damaged – allergy causing food particles or disease causing bacteria can enter the blood and cause more inflammation
      • And MANY chronic diseases, have their root in increased inflammation
  • You probably aren’t really a night owl – you just have too much caffeine late in the day, and expose yourself to too much blue light too close to bedtime
  • Shift work is VERY unhealthy because it disrupts your circadian rhythm
    • Shift workers are at a very high risk for colon cancer
  • From user data from Satchin’s app, called My Circadian Clock, Satchin has found that many people, while practicing time-restricted eating, see an improvement in acid reflux, as well as an improvement in sleep
  • Satchin eats his last meal at around 6pm

Intro

The Early Days

  • The large lifestyle difference between Satchin’s grandfathers:
    • Satchin’s maternal grandfather worked on the Indian railway, often during the night shift 
      • Years later, after retiring, Satchin’s maternal grandfather developed Alzheimer’s disease and passed away in his early 70s
    • As a contrast, his paternal grandfather worked on a farm, with no electricity 
      • He lived up until his early 90s with no cognitive impairments
    • “This really surprised me, how these two different lifestyles, led to a very different outcome”
  • When he was only 13, Satchin lost his father in a road accident – he was killed by a truck driver who was very sleep deprived
    • Satchin notes how it’s illegal to drive when you’re drunk, and there ways to measure how much alcohol you have in your blood
    • BUT – “We know that being sleep deprived is almost as dangerous or even more dangerous than driving drunk”
      • Why isn’t it illegal to drive when you’re sleep deprived?
      • We have no way to measure whether someone is sleep deprived

Time-Restricted Feeding – Part 1

  • In Satchin’s first time restricted feeding mouse study, he took mice from the same mother, identical in age and gender, and fed 1 group an around the clock high fat/high sucrose diet, and the other group the same diet, but with a limited 8 hour eating window
    • Both groups ate the same number of calories 
      • 60% of their calories were from fat, 20% from sucrose, and the rest from protein
    • After 18 weeks, it was found that the mice who followed the 8 hour eating window, weighed 28% less on average
    • Satchin repeated this experiment 3 times, with similar results each time
  • Time restricted eating and ketosis
    • After 12-16 hours without food, blood ketone levels begin to rise
      • After ~10 hours, ketone levels begin to rise in the cells that produce them
      • In another ~4 hours, you see a rise in the ketone levels in your blood 
    • “Some of the health benefits of time restricted feeding, may be mediated by this increase in ketone bodies”
  • Endurance
    • The mice that followed the time-restricted eating window in the above study, showed an increase in endurance
      • This is thought to originate from the presence of ketone bodies in the blood
  • What signals the start of the eating window?
    • Black coffee is fine in the morning – it does not signal the part of the eating window
      • BUT you CANNOT put cream and sugar in it

Obesity and Time-Restricted Eating

  • In one study, Satchin took obese mice, and had them follow a 9 hour time-restricted feeding diet
    • Over the next 13 weeks, the mice lost a large amount of fat (not muscle), and improved their glucose tolerance (this is a good thing)
  • Almost two thirds of the U.S. population is overweight or obese – more people should be restricting their eating windows

Sleep and the Dangers of Shift Work

  • Shift work is unhealthy because it disrupts your circadian rhythm
    • Shift work can be defined as “staying awake for 3 hours (or more) between 10pm and 5am, for at least once a week”
    • In that sense – “Almost everyone is a shift worker”
  • A sleep deprived brain:
    • Tricks us into thinking we’re more hungry – it miscalculates how much energy we really need for the rest of the day (causing you to eat more)
    • Makes bad decisions about food
      • In a typical day we make ~250 different decisions about our food alone (when to eat, what to eat, how much to eat etc.)
      • So we’re overeating the wrong things
  • Sleep deprivation, in combination with late night eating, causes more damage
    • During sleep we produce growth hormone that help repair damaged cells 
      • When we sleep less, we have less of this growth hormone present to repair our cells
    • When we eat late into the night, our stomach is thus working late into the night to digest the food – so the stomach cannot repair itself
    • Lack of growth hormone, in conjunction with food in the stomach, slows down the repair process
      • This causes damage in the gut which can accumulate
      • When the gut lining is damaged – allergy causing food particles or disease causing bacteria can enter the blood and cause more inflammation
  • The WHO has recently classified shift work as a potential carcinogen
  • Shift workers are at a very high risk for colon cancer
    • This is because they tend to eat late into the night, and have altered circadian rhythms – never really giving the gut the rest it needs

Chronotypes

  • This is the term for when you prefer to be awake (night owl vs. a morning lark)
  • The problem is, that most people force themselves to be night owls, either by drinking coffee too late in the day, or by exposing themselves to too much light close to bed time

The Importance of Darkness 

  • “In modern society, we’ve lost our right to darkness”
  • In our retinas, we have a blue light sensing protein called melanopsin present in ~5,000 cells
    • These proteins sense the blue spectrum of light
    • These cells, which contain melanopsin, are hard wired to the master circadian clock neurons in our brain
      • They’re also directly connected to meltaonin producing cells in the pineal gland
        • So exposure to blue light (by watching TV, or staring at your phone, or walking around in a brightly lit grocery store) reduces the amount of melatonin that your brain is producing, for several hours 
  • “As we are exposed to more light, we are likely to sleep less, and likely to make many more bad decisions like eating late at night, and eating unhealthy food”

Why do we need a strong eating/fasting rhythm, and a strong sleep/work cycle?

  • Just like your brain has to sleep to reset/repair/rejuvenate for another day, every organ in our body needs down time to repair and reset
    • “When your organs are repaired and rejuvenated, it’s almost like taking care of your car, getting the oil changed and tires rotated, on a daily basis”
    • Our circadian clock allows this to happen by:
      • Exposing us to light/darkness for defined intervals (sleep is essentially just darkness)
      • By producing hunger and satiety signals – so we’re in the “not hungry” stage for 12 hours or more per day
        • By obeying these hunger/satiety signals, we can give our organs the time they need for repair/rejuvenate
  • Most diseases are due to a lack of repair
    • When our gut is not repaired well (caused by eating late into the night), leaky gut can develop
      • This can lead to allergy causing chemicals entering the body, or disease causing bacteria entering the blood stream (thus causing inflammation)
      • MANY chronic diseases, have their root in increased inflammation
  • Our gut lining recycles every 10-15 days – so we have a new layer of cells every 10-15 days in our gut lining
    • Every day we are repairing 8-10% of our gut lining 

Another Interesting Mouse Study

  • Each one of us has genes that will predispose us to one or more diseases
  • Satchin took mice who “lacked an internal clock”  (caused by a lack of certain genes)
    • Because of this, the brains of these mice could not tell when to start/stop eating – this predisposes them to obesity 
    • They were then forced to follow a time-restricted eating regimen 
    • The mice were found to be “as healthy” as mice who have an internal clock, despite being predisposed to metabolic syndrome/obesity
  • Many humans have mutations in internal clock regulating genes, or mutations in melatonin receptor genes (thus altering how we feel the affects of melatonin) – Satchin estimates about 30-40% of the population
    • These people are at a high risk of obesity, type 2 diabetes, and certain cardiovascular diseases
    • Satchin’s mouse study, points to the fact that a time-restricted eating regimen might be able to override their predisposition to obesity

Human Time-Restricted Eating Study

  • Satchin describes a study out of the University of Alabama, which came out in 2018
    • Two groups of humans were examined
    • Both groups consumed the same number of calories
    • One group restricted their eating window to 6 hours, and the other for 12 hours
    • The 6 hour group had better insulin sensitivity, and lipid regulation 

My Circadian Clock

  • Satchin and his lab at Salk Institute developed this
  • People can participate in Satchin’s studies by using this app
  • From user data, Satchin has found that many people, while practicing time restricted eating, see an improvement in acid reflux, as well as an improvement in sleep

Sleep Trackers

  • Satchin wears and Oura Ring
    • Use the code “podcastnotes” at checkout for $50 off
  • There’s still lots of development to be done
    • For instance, how will the data collected from sleep trackers eventually be used to set healthcare prices?

Satchin’s Personal Life

  • Satchin’s mother used to have pre-diabetes, was overweight, and had high blood glucose levels
    • After restricting her eating window (slowly dialed back to not eating after 6pm) she adjusted well
    • She lost weight, and started sleeping more (about a half hour more each night)
    • Her fasting blood glucose levels also dropped
  • The typical day of someone in India
    • Indians tend to wake up early, to get stuff done before it becomes too hot during the day
    • They also tend to eat late in the day (dinner is often past 9pm)
    • Indians are eating more and more processed food
    • Satchin describes the typical day of a middle aged Indian living in a big city
      • They’ll wake up between 5-7 am and immediately have a cup of tea with cream and sugar, and eat highly processed biscuits 
      • They’ll then commute to work, usually an hour drive or so
      • In the office, they’ll eat a high carb lunch
      • They’ll then commute home
      • And in the evening, they’ll eat a late dinner around 9pm
    • Long commutes, rare access to healthy food, and over consumption of processed food is leading to high cholesterol, hypertension, and diabetes (or a combination of them all)
  • What does Satchin’s diet look like?
    • He wakes up around 6am
    • He eats a big breakfast around between 7:15-7:30am
      • Usually it’s oatmeal with cottage cheese, sometimes eggs, and some dried fruits
    • He usually skips lunch – if he needs to eat, he’ll have a small salad or a soup
    • Satchin is home by 5-5:30pm
    • He’ll then eat dinner around 6pm – this is his last meal for the day

Satchin’s Advice for Traveling (Heading East) and Jet Lag

  • Satchin says one of the worst things you can do, if you’re traveling where you’re prone to experience jet lag, is continuing to eat on your old time zone’s schedule
    • Once you land in the new time zone, eat (and sleep) on their schedul
    • Circadian rhythm, is very much tied to when you eat
  • You don’t need to at that much if you’re flying all day
    • Satchin reduces his calories by half on travel days
    • In flight, he usually doesn’t eat – he’d rather sleep
  • When Satchin reaches the new time zone, he’ll also usually go for a run as soon as he lands
  • To avoid the late afternoon sleepiness in the new time zone, don’t eat much of a lunch – just have a big breakfast
  • Check out these Podcast Notes for advice on how to avoid jet lag from Dr. Matthew Walker, author of Why We Sleep: Unlocking the Power of Sleep and Dreams

Wrapping Up

  • Satchin is starting a study to see if time-restricted eating will help people with metabolic syndrome
    • Nearly 10-12% of American adults have metabolic syndrome – that includes high BMI, abdominal obesity, glucose intolerance, or high cholesterol/triglycerides 
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