Most food studies, articles and blogs focus on WHAT we eat. There is another often overlooked factor that is equally important: WHEN. In this blog I’ll tell you the basics of time-restricted eating.
What is time-restricted eating?
Time-restricted eating – also known as ‘time-restricted feeding’ – is a form of intermittent fasting, where food intake is generally restricted to an 6 to 12 hour period per day. This results in a daily fasting period of 12-18 hours. Ideally, the eating window should fall within daylight hours. There are no restrictions of diet quality or quantity, so within the eating window, you can eat anything and as much as you want.
Benefits
The benefits of time-restricted eating are broad spectrum. Most people experience an increased overall feeling of wellbeing, health and energy. More specific:
- Better sleep quality
- Improved cognitive function
- Weight loss
- Better cardiovascular health (balancing cholesterol)
- Blood sugar control and prevention/reversal of diabetes type 2
- Increased production of ketone bodies
- Increased endurance
- Reduction of tumour growth (plus prevention of some cancers) and better immunity
- Increased DNA repair
- Enhanced stem cell function
- Improvements in gut microbiome and reduction of irritable bowel syndrome symptoms and acid reflux
- Lower levels of inflammation
- Prevention of of skin pathologies involving sun damage, skin aging, and skin cancer
It may therefore be no wonder time-restricted eating also increases longevity – with similar results as caloric restriction, but much easier to maintain. Many of these effects arise with 12 hrs of fasting, some more at 16 hours.
How time-restricted eating works
There are two main ways how time-restricted eating causes these beneficial effects. The first way is by implementing a daily fasting period. Eight hours after your last bite the body will enter the fasting state. Fasting has many health benefits, one of which is increasing autophagy. Autophagy is a natural cellular repair process which can lengthen both health-span (healthy and functional years) and lifespan. Most likely this is because of its positive effects on mitochondria (mitophagy) and stem cells. Also autophagy plays a protective role against the effects of advanced glycation end products (AGE’s). On top of that it reduces senescent cells.
The second mechanism of time-restricted eating is by aligning with circadian rhythms. Like all systems in the body the digestive tract is controlled by your biological clock. In fact: each organ has its own clock. For instance the secretion of enzymes by the liver and also the activity of the gut microbiome are timed. These clocks are mostly controlled by light, but the timing of meals also plays a role. If the clocks are synchronised, digestion will be optimal. However, this is a complex process that is not fully understood yet. Nevertheless this conclusion can be drawn: the body is not ready for the efficient digestion of food 24/7. The best time for eating is during the day and at the same time daily.
Common sense
Historically humans didn’t have access to food 24/7. Therefore we have adapted to function well in this context. Fasting meant there was no food available and therefore triggers the body to improve cognition and vitality to be able to find food. Food was usually found or caught during daylight hours; so it makes sense the human body is optimised to process food during the day. In the absence of food, the body will use this moment to scale up maintenance and repair. Because our environment has changed, we have to restrict food intake ourselves.
How to do time-restricted eating?
In its simplest form you have an early dinner and then stop eating. Eating is intake of anything but water; no exception for tea, coffee or alcoholic beverages. On top of that you can delay your breakfast, or stop eating after lunch – which is called early time restricted feeding (eTRF). At first you might feel hungry the moments that you used to eat at – your body is expecting food – but this subsides in a couple of days. The point is not to eat differently or less, but to eat the same food within the ‘feeding window’. It is no problem to cheat 1 or 2 days a week, which allows for some flexibility in social situations. This is not recommended in the beginning however. Don’t worry, once you have incorporated time restricted eating in your daily routine, it will become a habit without much effort. As said, you can eat whatever and as much as you want within your feeding window. Needless to say that if you make good choices there and eat normal amounts, this will add to the benefits.
OMAD
A special form of time-restricted eating is ‘one meal a day’ or OMAD. Here the feeding window is further restricted to two hours or less. Often this comes down to one large meal around lunchtime or dinner. To avoid deficiencies, it’s important to ensure this one meal is nutrient-dense. Hunger may be an issue for some, and this can be addressed by combining OMAD with a low carb or ketogenic diet. These diets will result in stable blood sugar levels.
Diseases that respond well to time-restricted eating
Clinical and preclinical studies suggest that time-restricted eating may provide benefits for several chronic diseases and metabolic conditions. Below is a list of diagnoses that have shown positive responses:
- Obesity
- Type 2 diabetes
- Cardiovascular disease
- Cancer
- Neurodegenerative diseases
- Autoimmune/inflammatory diseases
Contraindications, risks & side effects
As far as I know time-restricted eating can be done by anybody without risk. Make sure you don’t alter your diet adversely, by leaving out nutrients. Take care if you have a problem with blood sugar or hormone balance. In this case gradually restricting your food window – allowing the body to adapt – may be a good strategy.
Personal experience
I’ve been eating within a 6-10 hour window since 2016. Initially it took some effort, as I experienced hunger in the evening, but I got used to it pretty quickly. That was also because of the rapid onset of positive effects: better sleep and a clean and healthy feeling. Digesting food takes energy and it feels good to do this only a part of the day. Every now and then I eat in the evening, usually due to social factors, but this is only once or twice per month.
Time-restricted eating FAQ
Over the years I’ve encountered many questions about this subject. Below I will address the most important ones.
Is time-restricted eating safe?
Yes. There are little or no known risks. However, if you have a chronic disease and/or are taking several medications, then it is wise to slowly restrict your eating window – in steps of 30 or 60 minutes per week. This will give your body ample time to adapt.
I cannot stick to the protocol every day, is that a deal-breaker?
No. As long as you stick to the plan for 5-6 days per week, you will still be able to get some of the benefits of time-restricted eating.
Is time-restricted eating identical for men and women?
No, not fully. While both benefit metabolically, women may experience different weight loss outcomes and are more susceptible to menstrual cycle disruptions if fasting is too prolonged, or food intake is inadequate. Moderation is key: most women tolerate fasting windows below 16 hours well.
How about drinking coffee or tea outside the eating window?
Best to just drink water. However, drinking tea or black coffee (without sugar) every now and then will not be very detrimental.
Can I take supplements outside the eating window?
Do this as little as possible. In the case of sleep supplements (melatonin, magnesium, l-theanine) you have to make an exception. Many supplements should be taken with food anyway, so take these within your feeding window.
What is the difference between time-restricted feeding and time-restricted eating?
The term time-restricted feeding (TRF) is used in the context of animal research, where the animals are being fed. Time-restricted eating (TRE) is used in the context of humans.
Conclusion
Time-restricted eating is one of the best ways to improve your health and longevity. This science based intervention is simple, natural and free. It is an easy way to implement fasting (with many of its benefits) in your life, but without the discomfort and with little discipline required. I expect to continue this biohack the rest of my life.
Sources
1. Wikipedia: Fasting | Intermittent Fasting
2. The work of Dr. Satchidananda Panda (Salk Institute):
Website: www.mycircadianclock.org
Book: The Circadian Code
Ted Talk: Circadian habits, disease, light & eating
Interviews with Rhonda Patrick: Time-Restricted Feeding and Its Effects on Obesity, Muscle Mass & Heart Health and Practical Implementation of Time-Restricted Eating & Shift Work Strategies
3. Article by Dr. Rhonda Patrick on Found My Fitness: Time-restricted eating
4. Time Restricted Feeding review study from 2014
5. Autophagy and AGE’s: Spanish mini review from 2021 in ‘Frontiers in Cell and Developmental Biology’
6. Mice study in Cell Reports (2017): Time-Restricted Feeding Shifts the Skin Circadian Clock and Alters UVB-Induced DNA Damage
7. The Journal of Clinical Endocrinology & Metabolism (2022): Metabolic Efficacy of Time-Restricted Eating in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials
8. Systematic review and meta-analysis in Nature (2025): Effects of time-restricted eating with exercise on body composition in adults
9. Blog article by Peter Attia (2024): Does time-restricted eating increase the risk of cardiovascular death?
Author
‘Time-Restricted Eating’ was written by Dutch biohacker Tjeerd Verbeek (Biohackz) between 2018 and 2019.
The original title was ‘Time-Restricted Feeding’. Last revision and update: May 2025
Copyright
The text and images of this article may not be copied without permission of the author.
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