Thrive Action: Time restricted eating

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Vincenzo Malagoli

Thrive Action: Time restrict eating to the same 8 hrs daily

Difficulty: Low

Level: Foundational

Related to: UTT > Physical > Nutrition

Simple Recommendation: Restrict eating to 10am-6pm, 11am-7pm, or 12pm-8pm, depending on your lifestyle & chronotype.

I personally do 12pm-8pm because I'm more active later in the day and generally tend to go to bed later.

No need to be stressed or neurotic, but do your best to stay within 30-min window on either side.

Simple Concept: Fasted state creates beneficial conditions in a variety of body systems.

The body constantly moves between "fasted" and "non-fasted" states depending on blood glucose levels.

Non-fasted state, when glucose levels are high during and after eating, is associated with cell growth and inflammatory markers in the gut.

Fasted state, when glucose levels are low (typically 5-6 hours after the last solid or liquid calorie consumption), is associated with cellular repair, organ health, regular circadian gene expression, and cognitive clarity. Fasted state during sleep is especially important because it supports glymphatic clearing.

When done consistently for many months, regular fasted states improves fat lipolysis.

When you eat, both within a day and between days, is as important as what you eat.

Thrive Levers

Stabilized circadian rhythm

  • Mechanism - Normalizing a consistent rhythm of fasted and non-fasted states stabilizes gene expression related to the time of day.

Decrease digestive inflammation

  • Mechanism - Fasted states improve mucosal lining of the guy, decreases unhealthy high levels of lactobacillus, and stimulates the proliferation of beneficial gut microbiota. Fasted state decreases inflammation-related protein TNF-alpha as well cytokines IL-1 and IL-6. Taken together, this improves intestinal and digestive function.
  • This maybe particularly important for individuals suffering from guy biome issues such as irritable bowel syndrome (IBS)

Increase fat loss

  • Mechanism - Increases hepatic lipase (enzyme that metabolizes fat) and reduces CIDEC (lipid that inhibits lipolysis)

Improved liver function

  • Mechanism - Time restricted feeding increases brown fat stores. Brown fat is inversely correlated with non-alcoholic fatty liver deposits. This is a correlated and not direct mechanism.


  • Mechanism - Unknown. Higher blood glucose is correlated with mortality.

Cellular Autophagy

  • Mechanism - A fasted state promotes cellular repair via the AMPK pathway.

Glymphatic Clearing

  • Mechanism - Unknown.

Involved Body Systems

  • Digestive system via gut health
  • Urinary system via kidney health
  • Endocrine system via regulated circadian hormone expression
  • Lymphatic system via glymphatic clearing
  • Immune system via ??
  • Nervous system via greater cognitive clarity
  • Muscular system via muscle generation / maintenance
  • Reproductive system via sexual hormone regulation

Considerations and nuances

If you are trying time-restricted eating, transition slowly over the course of 7-10 days. Narrow an hour a day until target window to allow the hunger and digestion hormone systems to adjust.

Shifting the eating window mimics jet lag in the impact on circadian rhythm. Ideally, keep a consistent 8ish hr window each day (including weekend).

Three global rules that inform 8 hr window:

  1. Do not ingest food in the first hour after waking
  2. Do not ingest any solid or liquid calories in the 2-3 hours prior to bedtime
  3. Almost everyone tends to drift slightly based on life circumstances. Targeting an 8-hr window usually means a 10-hr window for most people.

Gastric emptying takes an average of 5-6 hrs, but depends on what we eat, when we eat, how much we eat, and our level of activity before eating.

There are ways to accelerate digestion and gastric empyting

  • Light movement (i.e. a brisk walk) or exercise for 20-30 minutes (i.e. high intensity interval training)
  • Glucose dispersal agents
  • gentle ones: cinnamon & lemon / lime juice
  • pharmaceutical ones: burburin and metformin (try with extreme caution)

Women that are menstruating or both men and women that are trying to get pregnant should not restrict below 8 hrs

  • Insufficient leptin signaling to the brain may communicate that there are not enough body resources for pregnancy and may impact ovulation and sperm counts thereby decreasing fertility

Triggering a non-fasted state is nuanced with some general rules

  • Anything that involves sugar, particularly simple sugars, will rapidly increase glucose and transition out of fasted state
  • Fats like MCTs (popular in bullet proof coffee, for example) likely do not trip out of a fasted state
  • Stevia and other artificial sweeteners, in moderation, likely do not trip out of a fasted state
  • Highly contextual based on when you last ate and what you last ate

For increasing muscle mass, one may want to eat protein earlier in the day because Bmal gene (related to muscle building) expression is more active earlier in the day

Consistent adherence is critical for beneficial impacts, so consider the social considerations of eating schedules for those around you (spouse, housemates, coworkers)

Some people do not do well on intermittent fasting either in terms of mood or hormone health

This may be difficult or have more nuanced considerations for people that work primarily at night

If you are feeling shaky or lightheaded, drink a glass with half a teaspoon of salt to stabilize blood volume

Support tools to consider

Open Questions

  • If wearing a continuous glucose monitor, what is the threshold for "fast broken"?
  • What turns on or off "sleep-related fasting"? If I fast for 2 hrs after waking, are those two hours in glymphatic clearing fasted state or is it the distinct waking fasted state?

Primary Source + Complete Notes: πŸŽ™ Huberman 041 - Effects of Fasting & Time Restricted Eating on Fat Loss & Health

Referenced Academic Articles:


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