Dr. Satchin Panda on Time Restricted Feeding and Its Effects on Obesity, Muscle Mass & Heart Health

In this video, Dr. Panda provides information on the human circadian clock, and simple measures that one can take to optimize circadian function. My notes and key takeaways are included below.


  • The first twenty minutes of the discussion are centered around the effects that light (as opposed to food) has on systems in the human body / the circadian clock. The remainder is mostly focused on the effects that food has on the circadian clock.
  • Almost every organ in our body has a form of internal clock, which determines when it operates at peak performance. This clock is strongly influenced by the level of ambient light.
  • There is a region in the brain called the Suprachiasmatic Nucleus (SCN) that regulates overall circadian function.
  • If scientists remove this brain region from a hamster, its sleep-wake schedule will become completely random. If a hamster that has had its SCN removed receives an SCN transplant from another hamster, its sleep rhythms will return to normal.
  • When light first hits the eyes in the morning, the master clock (The SCN) is immediately affected. Through intracellular signaling, it begins to radically alter gene expression, thereby creating the proteins that are required for daytime activities.
  • Bright light has actually been shown to significantly help combat depression.
  • Cortisol is responsible for 10-20% of all gene regulation. It is also one of the primary molecules responsible for triggering alertness. Melatonin on the other hand, induces drowsiness. Melatonin production is suppressed by light (in particular, blue light.)
  • Exposure to light seems to regulate the production of cortisol. Therefore, light can have significant effects on gene expression (via its effects on cortisol levels). 
  • At approximately 20 minutes into the episode, Dr. Patrick states that her mood improved significantly after she began living in a space that had better lighting.
  •  Dr. Patrick (and I) use an app called flux to reduce the amount of blue light that our computer screens emit during evening hours. It’s free, and seems to have a positive effect on my ability to fall asleep. That said, I do not believe flux has been subjected to any rigorous scientific testing as of yet.
  • Around 15 million Americans work shifts that are probably throwing off their circadian rhythms (evening shifts, night shifts, etc).
  •  When spending time outside on a sunny day, you will be exposed to approximately ten times more light than you would be when spending time in an office (even one that is brightly lit).
  •  The topic of the discussion switches to food at 26:30 in the video.
  • There are ideal times to eat and to fast. If you consume food at non-optimal times, digestion will be inefficient, and will create an excess of harmful metabolites. (Metabolites are byproducts of metabolic processes)
  • Biological clocks in organs involved in digestion are largely controlled by the consumption of food. Scientists came to this conclusion in part by observing differences between groups of lab animals that lived under the same light cycles, but were fed at different times.
  • For example, light has very little impact on the internal clock that regulates gene expression in the liver. This clock is primarily influenced by food consumption.
  • The functioning of many other organs outside of the brain are very strongly influenced by when we eat.
  • Time restricted feeding is defined at minute 34 as: “Eating within an 8 to 12 hour time window that begins when first food or drink enters your mouth.”
  • Restricting your consumption of food to within this time window has been shown to have many health benefits.
  • People who do shift work (night shift, evening shift, etc) are much more likely to develop metabolic diseases, heart disease, cancer, etc than those who don’t.
  • 36:00 – Dr. Panda describes and experiment in which groups of rats were given an identical diet, but differed in that the control groups could eat whenever they wanted, yet the experimental groups were only allowed to eat during 9 and 12 hour stretches of time. 
  • This is the list of benefits observed in the time restricted feeding group: (displayed at 37:32 in the video) 

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  • The ingestion of anything, aside from water, will effectively end a fast and start a feeding window. If you want to implement a time restricted feeding strategy into your life, aim to stop eating 8 to 12 hours after consuming your first non-water form of sustenance.
  • Time restricted eating has been shown to both reduce fat and increase lean muscle mass.
  • TRF appears to have positive effects on mitochondria volume, both in the liver and in brown fat.
  • The body seems to be able to repair itself far more easily in fasted states. This is one of the many reasons why TRF is beneficial for health.
  • 01:03:00 – Dr. Panda mentions that in a human trial, participants who underwent a time restricted feeding schedule reported sleeping better and feeling more energized during the day.
  • For those of you interested in participating in Dr. Panda’s research and using an app to structure your implementation of a time restricted feeding schedule, visit https://mycircadianclock.org. 
  • The top causes of death is developed countries are all chronic diseases. These diseases can be caused and or worsened by disrupted circadian rhythms.
  • The number one killer in industrialized societies is heart disease.
  • 1:15:00 – Discussion of the results of a time restricted feeding experiment that used fruit flies as test subjects. The flies on the restricted feeding schedule maintained heart health for a significantly longer amount of time than the control group.
  • These flies also slept better when their feeding windows were restricted. I have no idea how the quality of fly sleep is measured but I’d love to know.
  • Fly heart rate variability was also improved by the introduction of time restricted feeding.
  • The implementation of a TRF schedule seems to improve gut microbiome diversity. A diverse gut microbiome has been linked with positive health outcomes.


Key takeaways:

  • Slightly extending the amount of time you go without consuming food each day appears to be one of the best things you can do for your health.
  • In another video, Dr. Panda mentions that is best to refrain from eating for 1 to 2 hours after waking, and to cease eating 2 – 3 hours before going to bed. Out of all the many sleep hacks I have tried, this (stopping eating 2 – 3 hours before bed) has been the most effective. 


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