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In this Huberman Lab Essentials episode, I explore intermittent fasting and time-restricted eating, highlighting the positive benefits for weight loss, metabolism, organ health, circadian rhythms and cellular repair.
I explain a practical framework for designing a time-restricted eating window that aligns with your lifestyle, exercise schedule and social schedule. I also cover what breaks a fast, how to support fasting with tools like salt intake and post-meal walks, and the use of fasting-related supplements, including berberine and metformin.
Episode show notes:
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*Timestamps*
00:00:00 Intermittent Fasting, Time-Restricted Eating (TRE)
00:00:50 Diet, Weight Loss, Calories & Hormones
00:05:52 Body’s Response to Eating vs Fasting, Fasting Duration
00:09:04 Time-Restricted Feeding & Metabolic Benefits, Circadian Gene Rhythm
00:14:32 Optimal Meal Timing, Tool: Extend Sleep-Related Fasts
00:19:42 Eating Window Length, Tools: Adjusting TRE for Building Muscle, Regularity
00:22:34 Accelerate Transition to Fasting, Glucose Clearing, Tool: After-Meal Walk
00:24:16 Metformin, Berberine, Continuous Glucose Monitors; Cell Growth vs Repair, mTOR
00:27:25 Gut Microbiome; Transitioning to Intermittent Fasting & Individualization
00:29:43 Tool: 8-Hour Feeding Window & Weight Loss
00:31:05 What Breaks a Fast?, Sugar; Tool: Using Salt to Support Fasting
00:34:08 Tool: Ideal Feeding Window Guidelines; Exercise & Social Considerations
Disclaimer & Disclosures:
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Thank you for watching! If you enjoyed this topic and episode, please click the “Like” button and subscribe to our channel on YouTube. Thank you for your interest in science! — Andrew
Just been doing 16:8, break my fast at around 12 and last meal is 6 to 8pm, i feel so light and i can literally feel that my body loves the empty stomach, i want to start incorporating once a week 40 hour fasting as well.
Not to mention the positive effects of less exposure to the modern chain of processed food which is killing us slowly with metabolic syndrome.
The less times per day you eat all the garbage from which is impossible to escape from the better
Unless one controls the food we eat from the beginning till consumption
We are at risk of NCDs and cancer
At a more dire rate.
I love this, always great info. I am starting a weightless journey with water fasting this year. I hope every one can watch my videos. This info is so vital more people need to know. Ive been fasting for over 15 years. Thanks for the content.
I’ve just started a 15 day fast on day 2. Last time I did this was 2023 and I made it to 13 days hoping this one will get to 15 with lots of therapeutic results
Can you take berberine prior to sleep, or should it be 2-3 hours before?
I recently skipped eating lunches. I have lost about 6kgs in two months. I am so shocked the results are as so clear. I am looking to take that to next level. this video definitely got me some insight. thanks.
What about sugar free energy drinks? Lol
Dear Andrew Huberman,
I greatly appreciate your work and enjoy listening to your original English videos. Even though you speak quite fast, your voice and way of speaking are very pleasant to listen to.
Unfortunately, I cannot say the same about the German translation. Compared with many other German translations on YouTube, the German voice sounds less natural and is not as pleasant to listen to.
I hope you might consider improving the German voice in future videos. Your excellent content deserves an equally pleasant translation.
With great respect and appreciation.
Because my A1C was at 7 and I had fatty liver I started doing intermittent fasting. I stop eating at 9 PM and I start eating between 1 to 2 PM. After 4 months of following this, my fasting insulin test result was at an exceptional level and all my bloodwork was good except for the A1C. I walk 6 miles a day, I do yoga and meditate everyday, I am a 75-year-old woman. My next bloodwork is in mid October. Hoping that my A1C improves and that they take me off of being pre-diabetic. Regardless, I feel great and I’m gonna continue intermittent fasting as a way of life. Thank you for your clear, factual, and practical explanations. Your kindness oozes out of every cell of your body
Great video as always. Which is better for leaning out 16:8 Method vs 18:6 Method?
🙌🏻 Thank you! Absolutely amazing information—especially the part about how eating the SAME calories in a restricted window yields incredibly different results!! 😮
From Gemini (emphasis mine):
### I. Introduction & Principles of Dietary Science
* Core Focus: How time-restricted feeding (TRF) affects fat loss, muscle maintenance, organ/microbiome health, circadian biology, inflammation, exercise performance, and longevity.
* Calories In vs. Calories Out (CICO):
– References the 2018 Stanford study (Gardner et al., JAMA): When total calories are kept sub-maintenance, there is no significant difference in weight loss between a healthy low-fat diet vs. a healthy low-carbohydrate diet.
– CICO is the baseline requirement for weight change, but hormonal profile (insulin, thyroid, growth hormone, testosterone, estrogen) and daily activity dictate the "calories burned" side.
– Non-Exercise Activity Thermogenesis (NEAT)—fidgeting and minor body movement—can burn an extra 800 to 2,000 calories/day depending on the individual.
* The Physiology of Fed vs. Fasted States:
– Fed State: Blood glucose and insulin rise (steepness depends on food type—simple sugars produce the highest spike, fats the lowest). High insulin shifts cells toward dynamic growth (mTOR pathways).
– Fasted State: Insulin and glucose drop; counter-regulatory hormones like glucagon and GLP-1 rise to mobilize energy reserves (lipolysis). Cellular systems shift toward repair and autophagy.
—
‼️ ### II. Biological Foundations of Time-Restricted Feeding (TRF)
* The Landmark Satchin Panda Mouse Study:
– Mice fed a high-fat diet ad libitum (around the clock) gained weight, became obese, and developed fatty liver disease.
– ‼️ Mice fed the exact same caloric intake and high-fat diet restricted to an 8-hour window maintained/lost weight, protected liver health, and even reversed prior metabolic damage.
* Circadian Gene Expression:
– ~80% of human/animal genes oscillate on a 24-hour cycle. Eating continuously disrupts organ clock genes, while consistent daily feeding windows anchor metabolic rhythms and improve organ repair.
—
### III. Establishing the Ideal Feeding Window
* The Two Universal Non-Negotiables:
1. Morning Delay: Avoid consuming food/calories for at least 60 minutes after waking (and ideally longer).
2. Evening Cut-off: Avoid consuming food/liquid calories for 2 to 3 hours prior to bedtime. Eating close to sleep disrupts sleep-dependent autophagy and metabolic restoration.
* Window Duration & Placement:
– ‼️ 7–8 Hour Window (Sweet Spot): Optimal for metabolic benefits while maintaining high adherence.
– 4–6 Hour Window (Drawback): Often causes people to overeat or gorge during the compressed window, counteracting caloric goals.
– Ideal vs. Practical Placement:
* Biologically ideal: Mid-day window (e.g., 10:00 AM – 6:00 PM) to extend the overnight fast on both ends.
* Practically realistic: Noon to 8:00 PM window aligns better with social/family dinners while preserving the 2-3 hour pre-sleep buffer.
* Consistency Matters Most: Drifting your eating window by 2–3 hours on weekends offsets many of the circadian and metabolic benefits of TRF. Maintain a predictable window throughout the week.
—
### IV. Adjustments for Hypertrophy, Micro-Microbiome & Fasting Mechanics
* Muscle Growth/Maintenance:
– ‼️ For individuals prioritizing muscle maintenance or hypertrophy, consuming dietary protein earlier in the day (before 10:00 AM) favors muscle protein synthesis, regardless of when resistance training occurs.
* Gut Health & Microbiome:
– TRF reduces overgrowths of certain bacterial strains linked to metabolic disorders (like excess Lactobacillus) while increasing strains (Oscillibacter) that support healthy intestinal mucosal linings.
* What Breaks a Fast?
– ❗️ Safe: Water, plain black coffee, unflavored tea, pill-form caffeine.
– Context-Dependent: A single peanut or trace calorie will not break a fast deep into an overnight fast, but simple sugars or fruit juices will spike glucose and halt the fasted state immediately.
* Managing Lightheadedness During Fasting:
– ❗️ Low blood sugar/shakiness during a fast can often be remedied by putting a pinch of sea salt or Himalayan salt into water. Sodium helps stabilize blood volume and osmolality without breaking the fast.
—
### V. Accelerating the Transition: Glucose Disposal Strategies
* ❗️ Behavioral Glucose Clearing: Taking a light 20–30 minute walk immediately after a meal accelerates gastric emptying and clears blood glucose, transitioning the body from a fed to a fasted state hours faster than sitting sedentary.
* Pharmacological / Supplement Options:
– ‼️Compounds like Metformin (prescription) or Berberine (OTC) act as glucose disposal agents by lowering blood glucose and activating AMPK/sirtuins (mimicking a fasted cellular state).
– ❗️ Caution: Taking Berberine without sufficient dietary carbohydrates can induce severe hypoglycemia and headaches.
—
### VI. Summary Protocol Guidelines
1. Delay First Meal: Wait at least 60 minutes post-waking before eating.
2. Nighttime Buffer: Stop eating 2–3 hours before sleep.
3. Target Window: Aim for a consistent 8-hour daily feeding window (e.g., 12:00 PM to 8:00 PM).
4. Transition Gradually: Winnow down your eating window by ~1 hour per day over 3 to 10 days to allow hunger hormones (leptin, ghrelin) to adapt smoothly.
******
Timestamps from Gemini:
00:00:00 – Introduction & Overview of Intermittent Fasting Topics
00:00:45 – Defining Nutrition & The Stanford Weight Loss Study (Gardner et al., 2018)
00:03:00 – Calories In vs. Calories Out & Metabolic Factors (Hormones, NEAT)
00:05:50 – What Happens Mechanically When You Eat vs. Fast (Glucose, Insulin, GLP-1)
00:09:00 – Key Mouse Study on Time-Restricted Feeding & Circadian Rhythms (Panda Lab)
00:13:32 – How Fasting Benefits Liver Health & Cellular Processes
00:14:35 – Foundational Rules: Post-Waking & Pre-Bedtime Fasting Windows
00:15:25 – Determining the Ideal Feeding Window Placement (Sleep & Autophagy)
00:20:01 – Target Feeding Window Lengths (Why 7–9 Hours Beats 4–6 Hours)
00:20:38 – Early Protein Intake & Muscle Hypertrophy
00:22:33 – Accelerating the Transition to a Fasted State: Light Walks & Glucose Disposal Agents
00:25:58 – Cellular Growth (mTOR) vs. Cellular Repair (AMPK & Sirtuins)
00:27:27 – Gut Microbiome Benefits (IBS & Mucosal Lining)
00:28:12 – Individual Variations, Gender Differences, & Transition Protocols
00:29:43 – Human Study Evidence on 8-Hour Time-Restricted Feeding
00:31:07 – What Breaks a Fast? (Coffee, Tea, & Contextual Rules)
00:32:56 – Managing Fasting Symptoms with Salt/Sodium
00:34:08 – Practical Summary & Key Takeaways for Building Your Schedule
Intermitent fasting is nothing more than earing in a way more close to when we were more natural . No predator / omnivores has food available 24/7. We should all fast for a part of our day to mimick it .
What about coffee? If you have coffee within an hour with cream and delay your actual meal till 10 doesn’t coffee count as a meal as it has calories?
I started fasting 3 days a week and it has been a great experience. I document it on my channel.
I had gestational diabetes during my first pregnancy. Before my second kid I did a full one year of 16 or 18 hour IF, sometimes longer ones. Guess what, no gestational diabetes for my second pregnancy.
fyp
How about Carbonated Zero Drinks? Would they break fast?
I love how Professor cuts through all the noise around food and health and gets to the supportive science. I eat one low carb meal day and that’s it. I try to eat around lunchtime. I also walk my dog 6 miles a day rain or shine. At 75 years old I have so much energy and no underlying decease that I am aware. Plus thanks to Prof Hub I don’t drink any alcohol
Thanks to inflation my time restricting feeding is increasing . I am eating less throughout the day
Can't sleep past 6 am. 12 N to 3 PM. eating window. 10 PM bed time.
Why avoid eating during 1st hour after waking up? Insulin is anyway high (due to cortisol).
In Jainism the concept of diet says to eat in a window. And the window is after sunrise and stop before the sun sets… and not eating anything in this window
@hubermanlab Great content as always. You said that the ingesting protein early in the day is best for hypertrophy, should that be the first thing to have in the eating window or can i have it after 1 hour upon waking ?
Great stuff ! Since you also have knowledge in opthamology , can effective intermittent fasting eating Whole Foods and good protein help issues w eye floaters ? This happened suddenly and yes my snacking habits were awful but not anymore.
Sleep improved faster than weight loss when I shifted eating times. The circadian rhythm connection seems to lead everything.
seniors naturally intermittently fast. The results are devastating.
You are amazing ❤
What if I cannot fast at all because I have daily chronic headache ? Fasting can only worsening my headache
I've been experimenting with fasting for a few months, and it's interesting to learn the science behind why it works.
One meal a day( lunch) is a lifetime hack.
Can taking supplements break the fast?
I have always wondered what metformin does and For soem reason i could not find any info.. you gave it to me thanks!
In the Bible it says heal yourself thru fasting and prayer
This is purely anecdotal, but it is very interesting.
1) After doing IF for 12yrs I decided to take a break for the past 7 months and go back to a traditional breakfast and four meals per day. After weighing myself for the first time in seven months, I discovered that I gained 20lbs.
2) So I decided to return to IF with an 18:6 protocol. I took all the food I'd been eating over four meals and consumed the same food/identical calories in two meals per day. I also kept my daily steps, lifting, and cardio all the same.
**I've already dropped 4lbs in 2wks with no changes to food/calories or physical activity. The only change has been the 18hr fast with 6hr eating window. To me this is WILD.
Thanks very informative.
Just finished a 40 day fast
18 – 6 is the best !
🙂