Day and Night Biorhythm: Why We Live Against Our Biological Clock
Light, meal timing and activity set the rhythm of your body. When modern round-the-clock life runs against this rhythm, it can strain your glucose metabolism. Here you will find what lab studies show, what is observation and where the data end.
We talk a lot about what we eat. Hardly anyone asks when. Yet your body is not a machine that works the same way around the clock.
Natural rhythms are not romance. They are a timetable that hormones, insulin and cells follow.
Three in the morning. The light in the fridge is the brightest in the whole room. You stand in front of it, not really hungry, but not tired enough to sleep either.
Maybe you have just come home from a night shift. Maybe you were working, scrolling or watching series until a moment ago. Your head says: time for something to eat. Your body is not so sure.
Many people know this state. Tired during the day, awake at night, a weight that slowly creeps upward despite the same portions. And a blood sugar reading that, for the first time, lands in the borderline range at your GP's office.
This article is the deep dive on rhythm in the Guide to Natural Forces. It connects two worlds that are often told separately: chronobiology, the study of internal clocks, and metabolism with blood sugar and insulin. Morning light and screen light each have their own articles, which I link to. Here the question is: what happens in your metabolism when you live against your internal clock?
What you can expect here
- The zeitgeber concept
- How artificial light shifts the clock
- Misalignment in the lab
- Shift work and diabetes
- Meal timing as a zeitgeber
- Three levers and their limits
What is the day and night biorhythm?
Do you know the feeling after a long-haul flight? You have arrived, the sun is shining, but your body firmly believes it is the middle of the night. Hunger comes at the wrong time. So does sleep.
That feeling is a window into a system that otherwise works invisibly. Your body has an internal timekeeping of roughly 24 hours, the circadian rhythm. The word comes from Latin: circa diem, about a day.
Imagine an orchestra. The conductor sits in a tiny nucleus in the brain, the suprachiasmatic nucleus, directly above the crossing of the optic nerves. The musicians sit in the liver, the muscles, the fat tissue and the pancreas. Every organ has its own clock. For the piece to sound good, they all need to play in the same rhythm.
The zeitgeber concept in four steps
Human physiology- The internal clock runs on its own, but not at exactly 24 hours. Without signals from outside it would slowly drift out of sync.
- Zeitgebers reset it every day. The word is so German that it is used internationally as a technical term. Light, via special cells in the retina, is considered the strongest zeitgeber for the master clock in the brain.
- Meal timing and activity talk mainly to the organ clocks. Liver, fat tissue and muscle also orient themselves by when food arrives and when you move.
- Hormones carry the time of day into the body. Melatonin rises in the evening, cortisol in the morning. The pancreas is more prepared for food in the morning than late at night.
How light sets the master clock in detail is covered in Chronobiology: morning light and the internal clock. Here the focus is on what follows from this for metabolism.
Through the lens of Clinical Psychoneuroimmunology, this is a textbook example. The nervous system, the hormonal system and metabolism do not work side by side, but according to the same timetable. The immune system also follows daily fluctuations, but that is not the focus of this text.
Your body does not have one clock, but an entire clockwork. Health is not only about how well each individual clock runs, but how well they tick together.
And now you know why jetlag is felt not only in your head, but in your gut as well.
How modern life shifts the internal clock
Think of an ordinary winter day. You travel to work in the dark, sit under office lighting for eight hours and come home in the dark again. Then the ceiling lamp, the TV and your phone glow until shortly before you fall asleep.
For you, that is a normal day. For your internal clock, it is a strange day: too little light when it should be bright, and too much light when it should be dark.
A team led by Wright in Colorado compared people in their modern everyday lives with their rhythm after summer camping, with natural light only and no electric lighting.
In everyday life with artificial light, the participants got less sunlight during the day and more light after sunset, and their internal clock ran later. After camping, the internal biological night began roughly at sunset, and late chronotypes shifted earlier the most.
What this means for you: part of what feels like being a born night owl may have to do with your light environment.
Wright KP, McHill AW, Birks BR, Griffin BR, Rusterholz T, Chinoy ED. Curr Biol. 2013;23(16):1554-8. PMID: 23910656 · DOI: 10.1016/j.cub.2013.06.039 [Experimental study in humans]The same research group, led by Stothard, tested this in winter and over a single summer weekend.
In winter, too, the internal night and sleep began earlier after a week of natural light than in everyday life. One camping weekend achieved about 69 percent of the shift previously measured after a full week.
What this means for you: your internal clock is not set in stone. It appears to respond to light within days.
Stothard ER, McHill AW, Depner CM, et al. Curr Biol. 2017;27(4):508-513. PMID: 28162893 · DOI: 10.1016/j.cub.2016.12.041 [Experimental study in humans]On top of that, work and school often start earlier than many people's internal clocks would like. In 2006, Wittmann, Dinich, Merrow and Roenneberg called this gap between social and biological time social jetlag. In their survey of 501 volunteers, late chronotypes showed the largest differences between workdays and free days. A large epidemiological study led by Roenneberg later found that social jetlag was associated with a higher body mass index beyond sleep duration. That is an observation and not proof of a cause. More on evening light from screens can be found in Blue light, circadian rhythm and sleep.
A 2025 systematic review led by Kalkanis summarized 59 studies on sleep regularity. Irregular sleep times went along with more insulin resistance, a higher body mass index and high blood pressure, with moderate certainty of evidence. In five cohorts with a low risk of bias, the people with the most irregular sleep had a 20 to 88 percent higher mortality. Here too: association, not a proven cause.
Maybe you are not a hopeless evening person at all. Maybe you simply live in a world where it is never truly day and never truly night.
And now you know why winter in the office and evenings in front of a screen can together push your internal clock later.
When internal and external time drift apart: what happens in your metabolism
Not what, but when
I know this pattern very well. A middle-aged man, on rotating shifts for a long time. Early, late, nights, and a new rhythm every few days.
"I don't eat more than I used to. But I'm tired all the time, my belly is getting bigger, and now my sugar is off too."
When we went through his daily routine together, what stood out was less what he ate and more when. His largest meal was often in the middle of the night. After night shifts he saw hardly any daylight and slept in a bright room. His sleep times moved every week. His glucose metabolism values were in the borderline range.
The turning point was not a new supplement. It was a conversation about time: when light, when darkness, when the main meal, as far as his rota allowed. Over the following months he reported feeling more awake, and his follow-up values developed more favorably.
I cannot claim causality, but I document the temporal association. Many other things may also have changed during this period. The lesson from this pattern: sometimes the most important question about metabolism is not what, but when.
Why might the when matter so much? To understand this, researchers in Boston did something that would hardly be possible in everyday life. They deliberately pulled the internal clock and the external daily schedule apart in the lab.
A team led by Scheer had ten healthy adults live for ten days in a lab with 28-hour days. This way they gradually ate and slept at every phase of their internal clock.
When eating and sleeping were about 12 hours out of sync with the internal clock, the satiety hormone leptin dropped by 17 percent. Blood sugar rose by 6 percent even though there was 22 percent more insulin in the blood, and the daily rhythm of cortisol reversed entirely. In 3 of 8 evaluable people, blood sugar after meals was in a range typical of prediabetes.
What this means for you: just a few days against your internal clock can measurably change how your body handles sugar. However, this was a small, short lab study.
Scheer FA, Hilton MF, Mantzoros CS, Shea SA. Proc Natl Acad Sci U S A. 2009;106(11):4453-8. PMID: 19255424 · DOI: 10.1073/pnas.0808180106 [Pathophysiology, controlled lab study, n=10]More insulin, yet more sugar: that is the typical picture of lower insulin sensitivity. Imagine insulin as a key that opens the doors of your cells to sugar. With misalignment, the locks seem harder to open, and the pancreas has to send in more keys.
A team led by Morris used two eight-day lab protocols to separate three influences: the time of day of the internal clock, the external daily schedule and the misalignment between the two.
After the same meal, blood sugar was 17 percent higher in the biological evening at 8 pm than in the morning at 8 am, and the early insulin response was 27 percent lower. Misalignment alone raised blood sugar after meals by a further 6 percent, presumably through lower insulin sensitivity.
What this means for you: your internal clock appears to prepare your body for eating during the day. Late eating and misalignment could be two separate burdens.
Morris CJ, Yang JN, Garcia JI, et al. Proc Natl Acad Sci U S A. 2015;112(17):E2225-34. PMID: 25870289 · DOI: 10.1073/pnas.1418955112 [Pathophysiology, controlled lab study]Schematic sketch, not measured data. It summarizes the direction from the lab studies: in the biological morning the body can usually process sugar better than in the evening and at night.
A team led by Morris repeated the question with healthy people who had worked shifts for a long time. In two three-day lab visits, they simulated day work and night work in random order.
Under simulated night work, blood sugar after meals rose by 5.6 percent, despite 10 percent more insulin in the late phase. In the evening, blood sugar was 6.5 percent higher than in the morning.
What this means for you: years of getting used to shift work do not appear to fully protect the body from this burden.
Morris CJ, Purvis TE, Mistretta J, Scheer FA. J Clin Endocrinol Metab. 2016;101(3):1066-74. PMID: 26771705 · DOI: 10.1210/jc.2015-3924 [RCT, crossover, shift workers]And what if sleep deprivation is added to misalignment, as in the lives of many shift workers? A team led by Buxton kept healthy adults in the lab for five weeks. For three weeks they slept only 5.6 hours per 24 hours, on recurring 28-hour days. Resting metabolic rate dropped, and blood sugar after meals rose because the pancreas released too little insulin. After nine days of recovery sleep with a stable rhythm again, these values were back in the baseline range.
That is an encouraging message. In this study the burden was not permanent, but reversible as soon as sleep and rhythm returned.
An abnormal sugar value is not always just a question of discipline on your plate. Sometimes it is also a question of what internal time your body had to eat at.
And now you know why the same meal can be processed differently at three in the morning than at one in the afternoon.
Shift work and diabetes: what observational studies show
Nurses, firefighters, people in manufacturing, bus drivers, doctors. Without people who work at night, our society would not function. In return, they carry a burden that is rarely talked about.
A team led by Gan pooled 12 observational studies with 28 individual analyses, a total of 226,652 participants, including 14,595 people with diabetes.
Shift work was associated with a 9 percent higher diabetes risk (OR 1.09; 95 percent confidence interval 1.05 to 1.12). The association was stronger in men (OR 1.37) than in women (OR 1.09), and rotating shifts stood out in particular.
What this means for you: on average the risk rises moderately, not dramatically. This type of study cannot show whether shift work itself is the cause.
Gan Y, Yang C, Tong X, et al. Occup Environ Med. 2015;72(1):72-8. PMID: 25030030 · DOI: 10.1136/oemed-2014-102150 [Meta-analysis, observational studies]A team led by Vetter analyzed UK Biobank data from 272,214 working people on current shift work, and the entire working life for 70,480 people.
Those who worked mostly nights on rotating shifts had higher odds of type 2 diabetes (OR 1.44). More than 8 night shifts per month over a working life went along with OR 1.36. In permanent night workers the difference was not significant (OR 1.09; 0.93 to 1.27).
What this means for you: it may be not only the night, but above all the constant switching that is a burden. In this study, shift work did not amplify the genetic predisposition to diabetes.
Vetter C, Dashti HS, Lane JM, et al. Diabetes Care. 2018;41(4):762-769. PMID: 29440150 · DOI: 10.2337/dc17-1933 [Cross-sectional, cohort data]Another meta-analysis led by Wang, of 13 studies, found a 57 percent higher risk of metabolic syndrome with night shift work (RR 1.57), meaning the combination of belly fat, raised blood sugar, blood lipids and blood pressure. With longer night shift experience, the risk was RR 1.77.
What the lab data explain and what observation shows
Together, both levels form a plausible picture. They do not prove that the internal clock alone makes the difference. What is established: misalignment can strain glucose metabolism in the lab. What remains open is how large this share is in real life.
Checkups instead of self-experiments
If you work shifts long-term, have your blood sugar, long-term blood sugar (HbA1c), blood pressure, blood lipids and weight checked regularly by a doctor. Many employers also offer occupational health checkups for this.
If you take insulin or glucose-lowering medication, do not change your meal times or fasting periods without consulting your doctor. Prescribed medications are never adjusted to shifts, reduced or stopped on your own. This also applies to blood pressure medication. If you notice signs of low blood sugar such as shaking, sweating, a racing heart or confusion, take sugar immediately, and call 112 if consciousness is impaired.
Shift work is not a personal failure. It is a burden you share with your body. And burdens can be accompanied.
And now you know why regular checkups are more than a formality when you work shifts.
Meal timing as a zeitgeber: does it matter when you eat?
Breakfast standing up, a snack at your desk at lunchtime, and the first proper meal at nine in the evening. For many people this is not an exceptional day. It is everyday life.
Light sets the master clock. Food talks to the clocks in the liver and fat tissue. When the two signals do not match, the coordination in the orchestra could suffer. What do studies show?
A team led by Garaulet in Spain followed 420 people with overweight through a 20-week weight loss program. There, lunch is the main meal, and the researchers grouped participants by the time of this meal: before or after 3 pm.
The late eaters lost less weight and more slowly than the early eaters. Calorie intake, diet composition, estimated energy expenditure and sleep duration were similar.
What this means for you: the timing of your main meal could play a role in weight loss. However, this was not a randomized study, and late eaters also differed in other habits.
Garaulet M, Gómez-Abellán P, Alburquerque-Béjar JJ, Lee YC, Ordovás JM, Scheer FA. Int J Obes (Lond). 2013;37(4):604-11. PMID: 23357955 · DOI: 10.1038/ijo.2012.229 [Prospective observational study]A team led by Vujović compared late and early eating with identical food in adults with overweight or obesity. Physical activity, sleep and light were strictly controlled.
Late eating increased hunger, shifted the ratio of the appetite hormones ghrelin and leptin and lowered waking energy expenditure. In fat tissue, metabolic pathways shifted toward fat storage.
What this means for you: late eating could push toward weight gain through several pathways at once, via hunger, expenditure and fat tissue.
Vujović N, Piron MJ, Qian J, et al. Cell Metab. 2022;34(10):1486-1498.e7. PMID: 36198293 · DOI: 10.1016/j.cmet.2022.09.007 [RCT, crossover]A randomized study led by Jakubowicz assigned women with overweight and metabolic syndrome to two diets with the same calorie content for 12 weeks. One group ate most of its calories in the morning, the other in the evening. The morning group lost more weight, and insulin resistance and blood lipids developed more favorably: triglycerides fell by 33.6 percent there, while they rose by 14.6 percent in the evening group.
A team led by Sutton gave men with prediabetes enough food to maintain their weight. For five weeks they ate within an early 6-hour window with dinner before 3 pm, and for five weeks within a 12-hour window, in random order.
The early window improved insulin sensitivity, beta cell response, blood pressure, oxidative stress and appetite, even though weight stayed the same.
What this means for you: the timing of meals appears to have an effect of its own, independent of weight loss. The study was a small proof of concept, and the time windows are study conditions, not instructions.
Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Cell Metab. 2018;27(6):1212-1221.e3. PMID: 29754952 · DOI: 10.1016/j.cmet.2018.04.010 [RCT, crossover, controlled feeding]Early or midday, does it make a difference? A randomized study led by Xie with 90 healthy people without obesity compared an early with a midday eating window and a control group over five weeks. The early window improved insulin sensitivity more and was the only one to lower fasting blood sugar. A meta-analysis led by Rovira-Llopis of 18 studies with 1,169 participants comes to a similar picture. Overall, time-restricted eating lowered HbA1c and fasting insulin, but fasting blood sugar only in the studies with an early window. More on the classic model can be found in Intermittent fasting 16:8.
Not all fasting is the same. An eating window that stretches late into the evening is something different for your internal clock than one that is oriented to the day.
It is also important what these studies do not show. They are mostly small and short. They say nothing about decades. And they do not automatically apply to people on diabetes medication, to pregnant women or to people with a history of eating disorders. This is where what studies can reliably show ends.
And now you know why an early dinner can sometimes do more than a new diet.
What you can do: three levers for your rhythm
Maybe you are thinking now: that is all well and good, but my life has no room for sunrises and dinner at five. That is honest, and it is okay.
This is not about living like someone in the 18th century. It is about giving your body a few clear signals its clockwork can tune into. Energy is not a luxury. It is the freedom to shape your day yourself, instead of being driven by tiredness and cravings.
Directions, not recipes
- Bright during the day, dark at night. Part of your way outdoors in the morning, dimmed light in the evening, a dark bedroom. After night shifts, a darkened room for sleeping can be especially important. More in Chronobiology and morning light.
- Move your eating more into the day. The larger meal preferably earlier, the late meal rather small, and if possible no large portions in the middle of the biological night. If you take medication for diabetes, discuss it with your doctor first.
- Regularity before perfection. A roughly fixed wake-up time, even at weekends, is a strong anchor for your internal clock. With rotating shifts, fixed rituals such as having your main meal at the same time can provide stability. More in Putting sleep hygiene into practice.
In my clinical experience, the evening is often the easier place to start. Dimming the lights and eating earlier comes more easily to many people than getting up earlier. That is experience from consultations, not a study finding. Physical activity during the day can also be a timing signal, see Exercise as medicine at the cellular level.
How far each finding reaches
| Level | Finding | What it means |
|---|---|---|
| Controlled lab studies | Misalignment raises blood sugar and lowers insulin sensitivity, glucose tolerance is lower in the evening | Strong mechanism, but small groups and short duration |
| Randomized studies and meta-analyses | Early eating and early eating windows linked to more favorable metabolic values | Direction visible, studies small and short |
| Large observational studies | Shift work, social jetlag and irregular sleep associated with diabetes, weight and mortality | Clear associations, no statement about causes |
| Experiments with light | Natural light shifts the internal clock earlier | Well replicated, but in small groups |
You do not have to move back to nature to live with nature. It is enough for your day to have a morning again and your evening to have a night again.
And now you know why the question "When?" deserves just as much attention in your everyday life as the question "What?".
Frequently asked questions about the day and night biorhythm
What does the day and night biorhythm mean?
It refers to the circadian rhythm, an internal cycle of roughly 24 hours. A master clock in the brain and many clocks in organs such as the liver, muscle and fat tissue align sleep, hormones, body temperature and metabolism with the time of day. These clocks run on their own, but they need to be reset from the outside every day.
What are zeitgebers?
Zeitgebers are external signals that synchronize your internal clocks with the day. Light is considered the strongest zeitgeber for the master clock in the brain. Meal timing can help set the clocks in organs such as the liver and fat tissue in particular. Activity and sleep times are also discussed as timing signals.
How can shift work disrupt metabolism?
In lab studies from Boston, volunteers' daily schedules were shifted by about 12 hours against their internal clock. Afterwards their blood sugar was higher even though more insulin was released, the satiety hormone leptin dropped and the cortisol rhythm reversed. In people who had worked shifts for a long time, blood sugar after meals rose by 5.6 percent under simulated night work. This points to lower insulin sensitivity.
Does shift work increase the risk of diabetes?
Observational studies show an association. A meta-analysis with 226,652 participants found a 9 percent higher diabetes risk for shift work, more pronounced in men and with rotating shifts. In the UK Biobank, more than 8 night shifts per month over a working life were linked to 36 percent higher odds of type 2 diabetes. These studies cannot prove whether shift work itself is the cause.
Why is blood sugar higher in the evening than in the morning?
In one lab study, blood sugar after the same meal was 17 percent higher at 8 pm biological time than at 8 am, independent of sleep and fasting. In the evening, the beta cells of the pancreas released 27 percent less insulin in the early phase. So the internal clock appears to prepare the body for eating during the day rather than late in the evening.
Does it matter when I eat?
The research suggests it might. In a Spanish study with 420 people, late lunch eaters lost less weight during a weight loss program, with similar calorie intake. A controlled study found more hunger and lower waking energy expenditure with late eating. A meta-analysis on time-restricted eating saw a reduction in fasting blood sugar only with early eating windows. These are indications, not a fixed rule for everyone.
What is social jetlag?
Social jetlag describes the gap between the time your internal clock prefers and the time set by work or school. It shows up as a difference in sleep timing between workdays and free days. In a large survey, social jetlag was associated with a higher body mass index beyond sleep duration, as an observation without proof of cause.
Can I reset my internal clock?
The internal clock responds quickly to light. In studies from Colorado, the internal night shifted noticeably earlier in people exposed only to natural light. Just one weekend of camping achieved about 69 percent of the shift seen after a full week. Plenty of daylight in the morning and little artificial light in the evening are therefore obvious levers.
What can people who work shifts do?
You often cannot change your rota, but you can change some directions: anchors that are as regular as possible, such as fixed times for your main meal, darkness and quiet for sleep after a night shift, and no large meals in the middle of the biological night. If you work shifts, have your blood sugar, blood pressure and weight checked regularly by a doctor. Prescribed medications, such as those for diabetes, are never adjusted to shifts on your own, only under medical supervision.
Is early intermittent fasting suitable for everyone?
No. Studies on early time-restricted eating are mostly small and short. If you take insulin or glucose-lowering medication, changing your meal times puts you at risk of low blood sugar, so discuss it with your doctor first. During pregnancy and breastfeeding, with a history of eating disorders, with underweight, and in children and adolescents, fasting belongs under professional supervision.
Where the guide continues
This article is the deep dive on rhythm in the Guide to Natural Forces. The following texts pick up neighboring building blocks.
Chronobiology: morning light and the internal clock
How the master clock in the brain reads light, and what morning light has to do with cortisol and melatonin.
When your screen glows late into the eveningBlue light, circadian rhythm and sleep
Why light in the evening can shift the internal clock, and what of this matters in everyday life.
When rhythm starts with sleepPutting sleep hygiene into practice
What matters according to the research and what is overrated, from wake-up time to the bedroom.
When you are thinking about eating windowsIntermittent fasting 16:8
What happens in the body when breaks between meals get longer, and who should be cautious.
When you want to know how much sun makes senseHow much sun does the body need
Sun as a question of dose, depending on skin type, time of day, season and where you live.
When you want to understand what exercise triggers in the cellExercise as medicine at the cellular level
Why training can be thought of as a dosed stimulus that triggers adaptations in the body.
When your day is mostly spent sittingSitting and lack of exercise
Why prolonged sitting can be a topic of its own for metabolism and blood vessels.
When you are looking for the big pictureLifestyle as therapy for mind and body
Why sleep, light, food and exercise can be thought of as part of a treatment.
Scientific sources
- Scheer FA, Hilton MF, Mantzoros CS, Shea SA. Adverse metabolic and cardiovascular consequences of circadian misalignment. Proc Natl Acad Sci U S A. 2009;106(11):4453-8. PMID: 19255424 · DOI: 10.1073/pnas.0808180106 [Pathophysiology, controlled lab study, n=10]
- Morris CJ, Yang JN, Garcia JI, et al. Endogenous circadian system and circadian misalignment impact glucose tolerance via separate mechanisms in humans. Proc Natl Acad Sci U S A. 2015;112(17):E2225-34. PMID: 25870289 · DOI: 10.1073/pnas.1418955112 [Pathophysiology, controlled lab study]
- Morris CJ, Purvis TE, Mistretta J, Scheer FA. Effects of the Internal Circadian System and Circadian Misalignment on Glucose Tolerance in Chronic Shift Workers. J Clin Endocrinol Metab. 2016;101(3):1066-74. PMID: 26771705 · DOI: 10.1210/jc.2015-3924 [RCT, crossover, shift workers]
- Buxton OM, Cain SW, O'Connor SP, et al. Adverse metabolic consequences in humans of prolonged sleep restriction combined with circadian disruption. Sci Transl Med. 2012;4(129):129ra43. PMID: 22496545 · DOI: 10.1126/scitranslmed.3003200 [Pathophysiology, controlled lab study]
- Gan Y, Yang C, Tong X, et al. Shift work and diabetes mellitus: a meta-analysis of observational studies. Occup Environ Med. 2015;72(1):72-8. PMID: 25030030 · DOI: 10.1136/oemed-2014-102150 [Meta-analysis, k=12 studies, n=226,652]
- Vetter C, Dashti HS, Lane JM, et al. Night Shift Work, Genetic Risk, and Type 2 Diabetes in the UK Biobank. Diabetes Care. 2018;41(4):762-769. PMID: 29440150 · DOI: 10.2337/dc17-1933 [Real-world cohort data, cross-sectional, n=272,214]
- Wang F, Zhang L, Zhang Y, et al. Meta-analysis on night shift work and risk of metabolic syndrome. Obes Rev. 2014;15(9):709-20. PMID: 24888416 · DOI: 10.1111/obr.12194 [Meta-analysis, k=13 studies]
- Wright KP, McHill AW, Birks BR, Griffin BR, Rusterholz T, Chinoy ED. Entrainment of the human circadian clock to the natural light-dark cycle. Curr Biol. 2013;23(16):1554-8. PMID: 23910656 · DOI: 10.1016/j.cub.2013.06.039 [Experimental study in humans, field conditions]
- Stothard ER, McHill AW, Depner CM, et al. Circadian Entrainment to the Natural Light-Dark Cycle across Seasons and the Weekend. Curr Biol. 2017;27(4):508-513. PMID: 28162893 · DOI: 10.1016/j.cub.2016.12.041 [Experimental study in humans, field conditions]
- Wittmann M, Dinich J, Merrow M, Roenneberg T. Social jetlag: misalignment of biological and social time. Chronobiol Int. 2006;23(1-2):497-509. PMID: 16687322 · DOI: 10.1080/07420520500545979 [Cross-sectional, survey, n=501]
- Roenneberg T, Allebrandt KV, Merrow M, Vetter C. Social jetlag and obesity. Curr Biol. 2012;22(10):939-43. PMID: 22578422 · DOI: 10.1016/j.cub.2012.03.038 [Cross-sectional, epidemiological]
- Kalkanis A, Lenkens D, Steiropoulos P, Testelmans D. Sleep regularity as an important component of sleep hygiene: a systematic review. Sleep Med Rev. 2025;84:102203. PMID: 41259946 · DOI: 10.1016/j.smrv.2025.102203 [Systematic review, 59 studies]
- Garaulet M, Gómez-Abellán P, Alburquerque-Béjar JJ, Lee YC, Ordovás JM, Scheer FA. Timing of food intake predicts weight loss effectiveness. Int J Obes (Lond). 2013;37(4):604-11. PMID: 23357955 · DOI: 10.1038/ijo.2012.229 [Real-world intervention cohort, prospective, n=420]
- Vujović N, Piron MJ, Qian J, et al. Late isocaloric eating increases hunger, decreases energy expenditure, and modifies metabolic pathways in adults with overweight and obesity. Cell Metab. 2022;34(10):1486-1498.e7. PMID: 36198293 · DOI: 10.1016/j.cmet.2022.09.007 [RCT, crossover]
- Jakubowicz D, Barnea M, Wainstein J, Froy O. High caloric intake at breakfast vs. dinner differentially influences weight loss of overweight and obese women. Obesity (Silver Spring). 2013;21(12):2504-12. PMID: 23512957 · DOI: 10.1002/oby.20460 [RCT, 12 weeks]
- Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Early Time-Restricted Feeding Improves Insulin Sensitivity, Blood Pressure, and Oxidative Stress Even without Weight Loss in Men with Prediabetes. Cell Metab. 2018;27(6):1212-1221.e3. PMID: 29754952 · DOI: 10.1016/j.cmet.2018.04.010 [RCT, crossover, controlled feeding]
- Xie Z, Sun Y, Ye Y, et al. Randomized controlled trial for time-restricted eating in healthy volunteers without obesity. Nat Commun. 2022;13(1):1003. PMID: 35194047 · DOI: 10.1038/s41467-022-28662-5 [RCT, n=90]
- Rovira-Llopis S, Luna-Marco C, Perea-Galera L, Bañuls C, Morillas C, Victor VM. Circadian alignment of food intake and glycaemic control by time-restricted eating: A systematic review and meta-analysis. Rev Endocr Metab Disord. 2024;25(2):325-337. PMID: 37993559 · DOI: 10.1007/s11154-023-09853-x [Meta-analysis, k=18 studies, n=1,169]