Fasting for beginners: the gentle path from 12 to 16 hours without a crash
Most people start with 16:8 and stop again after ten days. Yet the standard scientific review itself says that the eating window should shrink gradually over months. Here is the slow path.
Your metabolism is not a light switch. It is a muscle that learns. What decides the outcome is not the length of the fast, but whether your body is given time to switch over.
Sunday evening. You have listened to a podcast, you have made up your mind. From tomorrow, 16:8. Nothing before twelve, last meal at eight. Sounds doable.
Monday is fine. Tuesday at half past ten you have a headache. Wednesday you are thin-skinned in a meeting and do not quite know why. Thursday you eat a bar at half past ten because it simply does not work any more. Friday you think: fasting is probably not for me.
I hear this story often. And I find it a shame, because the mistake almost never lies in the person. It lies in the starting point.
Because here is something that surprises many people: in perhaps the most cited review on intermittent fasting, published in 2019 in the New England Journal of Medicine, it says in black and white that the daily eating window should be reduced gradually over several months. Not over a weekend. Over months.
What awaits you in this article
- Why the jump to 16:8 is bigger than it looks
- The metabolic switch: when ketone bodies actually rise
- Metabolic flexibility as the real goal
- What happens in body and mind in the first weeks
- The stepwise scheme from the NEJM review in detail
- Early or late: where the eating window belongs
- What intermittent fasting can do and what the studies do not show
- Protein, resistance training and keeping muscle mass
- Women and fasting: an honestly thin evidence base
- When fasting is not a good idea
- Three levers for your first week
The jump that nobody calls a jump
Imagine someone told you: from tomorrow you run ten kilometres every day. You have not trained so far. Nobody would recommend that. With eating rhythms we do it all the time anyway.
How big the jump really is becomes visible in one number from the study by Wilkinson and colleagues. The group at the Salk Institute and the University of California San Diego studied people with metabolic syndrome. The inclusion criterion was a daily eating window of at least 14 hours. That is the normal case. First coffee with milk at seven, last snack at half past nine in the evening.
Wilkinson and a team from San Diego and La Jolla had 19 people with metabolic syndrome eat for twelve weeks within a self-chosen 10 hour window. Most of them were taking statins or blood pressure medication at the same time, so standard therapy continued.
What is remarkable for me is less the result than the starting point: the inclusion criterion was a previous eating window of 14 hours or more. The study target was 10 hours, not 8. The authors explicitly describe time restricted eating as a lifestyle measure that may come in addition to normal medical treatment, not as a replacement for it.
Wilkinson MJ, Manoogian ENC, Zadourian A et al. Cell Metab. 2020;31(1):92-104.e5. DOI: 10.1016/j.cmet.2019.11.004 [Real-world, single-arm intervention study, n=19]Going from 14 to 8 hours means cutting six hours of habitual eating time in one stroke. And not in theory, but precisely in the hours in which your body has been expecting supplies for years.
We treat 16:8 as an entry level because it is the most popular number. In the literature, 16:8 is in fact more of a target state than a starting point.
That takes the pressure off. If your first step goes from 14 to 12 hours, you are not being too soft. You are closer to what the reviews themselves propose.
The metabolic switch and when it really clicks
I like this picture: your body has two tanks. In the first there is sugar, in the second fat. The sugar tank is small and fast. The fat tank is huge and slow. In most people the engine runs almost exclusively from the first tank, because it is constantly being topped up.
The change between the two tanks has a name. In the scientific literature it is called metabolic switching. And it has a point in time.
The review by de Cabo and Mattson in the New England Journal of Medicine describes the course in humans precisely. In the fed state, ketone bodies in the blood are low. They rise within 8 to 12 hours after the start of fasting and reach values of 0.2 to 0.5 millimoles per litre. This level is held over 24 hours, after which a further rise to 1 to 2 millimoles per litre follows at 48 hours.
Both authors add a sentence that concerns the whole beginner question: the timing of this response gives an indication of which fasting periods make sense in intermittent fasting schemes.
de Cabo R, Mattson MP. N Engl J Med. 2019;381(26):2541-2551. DOI: 10.1056/NEJMra1905136 [Review, NEJM review]Read that again. Eight to twelve hours. Not sixteen.
The review by Anton and colleagues at the University of Florida and the National Institute on Aging puts it similarly. It defines the switching point as the moment of negative energy balance at which the glycogen stores of the liver are emptied and fatty acids are mobilised, typically beyond 12 hours after the last intake of food.
Time window in which ketone bodies in the blood begin to rise in humans
Millimoles per litre of ketone bodies, then held over 24 hours
Period within which the initial side effects usually disappear, according to the NEJM review
Why the switching itself is the gain
Now comes the part I find most interesting. It is not primarily about spending as many hours as possible in fat metabolism. It is about your body managing the change cleanly.
There is a technical term for that: metabolic flexibility. The review by Goodpaster and Sparks defines it as the ability to respond and adapt to changing metabolic demands. Its opposite, metabolic inflexibility, they describe as a typical feature of obesity and type 2 diabetes.
After the meal
Glucose from the food is the main fuel. Insulin is high, fat is stored rather than mobilised. That is entirely normal and no problem, as long as it is not the permanent state.
The liver takes over
The glycogen stores of the liver keep blood sugar stable. Insulin falls slowly. Nothing dramatic is happening yet, but the course is starting to be set.
The switching begins
Triglycerides are broken down into fatty acids and glycerol, and the liver builds ketone bodies from them. According to the NEJM review they rise measurably in this window. The brain gets a second source of fuel.
Fatty acid oxidation as the main mode
The respiratory quotient falls, meaning the ratio of exhaled carbon dioxide to oxygen taken up. It is exactly this marker that the NEJM review describes as a sign of greater metabolic flexibility in the shift to fatty acids and ketone bodies.
Ravussin and a team at the Pennington Biomedical Research Center had eleven adults with overweight eat for four days each in an early window from 8 am to 2 pm and four days in the control rhythm from 8 am to 8 pm. Calorie amount and meal frequency were identical, and on the fourth day the 24 hour energy expenditure was measured in the metabolic chamber.
Energy expenditure did not change. Other things did change: the ghrelin level fell on average by 32 picograms per millilitre, hunger became more even across the day, metabolic flexibility rose and the non-protein respiratory quotient over 24 hours fell.
For you that means: an early window seems to work less through expenditure than through appetite and fuel choice. That is a small study. It is, however, very cleanly controlled.
Ravussin E, Beyl RA, Poggiogalle E, Hsia DS, Peterson CM. Obesity (Silver Spring). 2019;27(8):1244-1254. DOI: 10.1002/oby.22518 [RCT, crossover, n=11]And now you know why with beginners I do not ask about hours, but about how it feels at eleven in the morning. Someone who wobbles during the switch does not have a willpower problem. The switch is just rusty.
The first weeks are the hardest, and that is documented
May I ask you an uncomfortable question? Did anyone tell you that it is allowed to feel bad at the beginning?
Probably not. In most articles intermittent fasting sounds as if you would be floating from day three. The standard scientific review says something else, and remarkably directly.
When switching to an intermittent fasting scheme, many people experience hunger, irritability and reduced ability to concentrate. These initial side effects usually disappear within a month, and patients should be advised of this fact.
Paraphrased from de Cabo and Mattson, New England Journal of Medicine 2019I find this sentence important for two reasons. First: the complaints are normal and to be expected. Second: they have an expiry date. About a month.
Someone who does not know that reads the Wednesday headache as proof that fasting is harmful, or that they cannot do it. Someone who does know it files it as a transitional phenomenon and makes the step smaller instead of giving up.
Finnell and a team reviewed the charts of 768 medically supervised fasting courses from an inpatient facility. What was involved there was considerably longer fasting than 16 hours, namely at least two consecutive days without food.
Of the adverse events recorded in total, 75 per cent were mild, and the authors describe them as known responses to fasting. In 555 stays the most severe event was grade 2 or below, in 212 stays grade 3, and in a single one grade 4. Serious events occurred in 2 of 768 stays.
That is not a free pass. It is confirmation that the typical accompanying effects are mainly mild when there is medical supervision. And that the rare serious cases exist, which is why that supervision is needed.
Finnell JS, Saul BC, Goldhamer AC, Myers TR. BMC Complement Altern Med. 2018;18(1):67. DOI: 10.1186/s12906-018-2136-6 [Real-world, chart review of 768 treatment courses]This review concerns multi-day water fasting under supervision, not a 14 hour window in everyday life. I cite it because it describes the spectrum of typical complaints well, not because the numbers would be transferable to intermittent fasting. With daily time restricted eating the burden is incomparably smaller.
Why the mind joins in at the beginning
There is a second level, and it is psychological. The analysis by Trepanowski and colleagues at the University of Illinois at Chicago compared alternate day fasting with daily calorie restriction over twelve months. The dropout rate was highest in the fasting group, namely 13 of 34 participants, compared with 10 of 35 in the calorie restriction group and 8 of 31 in the control group.
The weight results were practically the same between the two groups. What differed was staying with it. And the participants in the fasting group ate more than intended on fasting days and less on feast days. The body steered against the plan.
We judge fasting plans by their theoretical effectiveness. What matters, though, is how many weeks you actually stay with it.
A 12 hour window that you keep for twelve months is dearer to your metabolism than a 16 hour window that ends after eleven days. And now you know why I prefer to understate things at the start.
The stepwise scheme: as it stands in the review
Now to the concrete part. The NEJM review contains an example scheme for what a gradual entry into time restricted eating may look like. The authors write that physicians can advise their patients to reduce the daily eating window gradually over a period of several months, with a goal of 16 to 18 hours of fasting per day.
Example scheme from de Cabo and Mattson 2019
Eating window per day and days per week, following the example printed in the review. The starting point of 14 hours and more comes from the inclusion criterion of the study by Wilkinson and colleagues.
Three things stand out about this scheme, and all three contradict what is usually recommended.
First: the first step is 10 hours, not 8. For someone starting at 14 hours, even that is still a jump. I therefore consider an intermediate step at 12 hours sensible, and I say alongside that this is my clinical assessment and does not appear in the scheme.
Second: in the first three months it is 5 days a week, not seven. Two days without a rule are built in. Not as a reward, but as a design principle.
Third: the target state is only reached in the fourth month. Four months. Not four days.
This scheme is an example from a review, not an individual treatment plan. It was described for adults without the contraindications named further below. Which steps suit you depends on your everyday life, your starting weight, your findings and your medication. That belongs in a personal conversation, not in a table.
A pattern I meet again and again
A picture I often hear in conversations: someone has already started with 16:8 three times and stopped three times after one or two weeks. By the fourth attempt the question is no longer whether it works, but whether there is something wrong with the person.
What often stands out in these conversations is not a lack of discipline. It is the size of the first step. If we instead begin with a cleanly kept 12 hour window on five days, for example eight in the morning to eight in the evening, the topic of failure often disappears from the conversation completely. Only after that do we talk about the next step.
The lesson I take from it: the best fasting step is the one you find boring. With habits, boredom is a mark of quality.
Early or late: where the window belongs
If you shrink the eating window, you have to decide which end to cut. Do you drop breakfast or the late dinner?
Most people drop breakfast because it sounds easier. The data speak rather for the opposite.
Sutton and a team at the Pennington Biomedical Research Center conducted the first supervised controlled feeding study to test whether intermittent fasting has effects independently of weight loss. Men with prediabetes ate for five weeks in a 6 hour window with dinner before 3 pm, then in the control scheme with a 12 hour window, or in the reverse order.
The framing is decisive: the participants were given enough to eat to maintain their weight. Even so, insulin sensitivity, beta cell responsiveness, blood pressure, oxidative stress and appetite improved.
For you that means: it could be not only about how much you eat, but also when. That was a small proof of concept study in men with prediabetes, so not evidence for all people and all situations.
Sutton EF, Beyl R, Early KS, Cefalu WT, Ravussin E, Peterson CM. Cell Metab. 2018;27(6):1212-1221.e3. DOI: 10.1016/j.cmet.2018.04.010 [RCT, crossover, supervised feeding study]Jamshed and a team at the University of Alabama at Birmingham compared an early 8 hour window from 7 am to 3 pm with a window of 12 hours and more over 14 weeks. Both groups received the same weight loss support. 90 adults with obesity took part, 80 per cent of them women.
The early window was superior for weight, with a difference of 2.3 kilograms. Diastolic blood pressure improved by 4 millimetres of mercury, and mood changed favourably, specifically fatigue, vigour and dejection. For body fat overall the difference was not significant. The authors convert the effect into an additional calorie saving of about 214 kilocalories per day.
Jamshed H, Steger FL, Bryan DR et al. JAMA Intern Med. 2022;182(9):953-962. DOI: 10.1001/jamainternmed.2022.3050 [RCT, n=90, 14 weeks]The counter-test comes from a study in Boston. Vujović and a team at Brigham and Women's Hospital and Harvard Medical School had people with overweight eat the same meals once early and once late, with strictly controlled nutrient intake, movement, sleep and light exposure.
Late eating increased hunger, shifted the ratio of ghrelin to leptin, lowered energy expenditure in the waking state and changed gene expression in adipose tissue in the direction of less fat breakdown and more fat build-up. At identical calorie intake.
When we think about fasting we think in terms of going without. The studies on timing suggest that it is just as much about synchronisation: eating when your metabolism is set up for it.
In practice that means for the start: if you cut from 14 to 12 hours, cut in the evening if possible. So rather bring the late dinner forward than drop breakfast. And now you know why I almost never ask beginners whether they want to skip breakfast.
What fasting can do, and where the data are honestly thin
This is where it gets uncomfortable, and I think that belongs here. Intermittent fasting is not a magic trick. The largest randomised study on 16:8 came to a rather sober result.
Lowe and a team at the University of California San Francisco compared 16:8 with three structured meals per day over twelve weeks. 116 people with overweight or obesity took part, and the fasting group ate freely between 12 noon and 8 pm.
Weight did fall significantly in the fasting group, but the difference between the groups was not significant. And in the subgroup that was examined in person, a significant difference showed in the appendicular lean mass index, meaning muscle mass in arms and legs. The authors' conclusion: time restricted eating without further measures is not more effective for losing weight than eating spread across the day.
Lowe DA, Wu N, Rohdin-Bibby L et al. JAMA Intern Med. 2020;180(11):1491-1499. DOI: 10.1001/jamainternmed.2020.4153 [RCT, n=116, 12 weeks]Other work comes to friendlier, but likewise moderate results. Cienfuegos and a team at the University of Illinois at Chicago compared a 4 hour with a 6 hour window against a control group over eight weeks. Both fasting variants led to comparable reductions in body weight of about 3 per cent, and in insulin resistance and oxidative stress. Energy intake fell by around 550 kilocalories per day, without anyone counting calories.
The summarising review by Varady and colleagues across all forms of fasting names mild to moderate weight reductions of 1 to 8 per cent compared with baseline and consistent reductions in energy intake of 10 to 30 per cent. It describes intermittent fasting overall as safe and records that it did not lead to drops in energy or to increased disordered eating behaviour.
Established by randomised trials: time restricted eating may lower energy intake and favourably influence individual metabolic markers. Mechanistically plausible, but not yet established in humans with large endpoint trials: that gradually approaching a smaller eating window brings better long term results than starting directly. Clinical assessment without a strong study basis: that the intermediate step at 12 hours is the decisive difference for many people. What I describe here is a reasoned position, not a proven rule.
Muscle, protein and the question of resistance training
If you shrink an eating window, you usually eat less. And if you eat less, you do not only lose fat. That is the point at which many beginner guides stop telling the story.
In the feasibility study by Chow and a team at the University of Minnesota, participants ate for twelve weeks in an 8 hour window. Weight, fat mass and visceral fat fell. So did fat free mass, by about 3 per cent. No accompanying training programme was planned.
Moro and a team at the University of Padua had 34 resistance trained men eat for eight weeks either in an 8 hour window or in their normal rhythm. Both groups received the same calorie amount and the same nutrient distribution, with about 22 per cent protein, and completed the same standardised resistance training programme.
Fat mass fell more strongly in the fasting group. Fat free mass, muscle cross section in arm and thigh, and maximal strength were maintained in both groups. What stood out was a decline in testosterone and IGF-1 in the fasting group, without muscle mass or strength suffering from it. The twelve month follow-up study by the same working group confirmed this picture.
Moro T, Tinsley G, Bianco A et al. J Transl Med. 2016;14(1):290. DOI: 10.1186/s12967-016-1044-0 [RCT, n=34, with resistance training]The difference between these two studies is for me the practically most important message of this article after the stepwise scheme: a smaller eating window without resistance training and without a look at the protein amount is half a strategy.
Women, the cycle and an evidence base I do not want to talk up
The review by Cienfuegos and colleagues on reproductive hormones summarises the available human studies. In premenopausal women with obesity, androgen markers fell under intermittent fasting, meaning testosterone and free androgen index, while sex hormone binding globulin rose. This effect occurred more readily when eating took place earlier in the day. No effect showed on oestrogen, gonadotropins and prolactin.
The authors themselves write, however, that very few studies exist on this topic and that hardly any robust conclusions can be drawn at present. They discuss possible advantages in polycystic ovary syndrome as well as possible disadvantages in men.
My conclusion from that, and I name it as mine: with women, start more slowly, prefer the early window, observe cycle, sleep and energy level. And if things change, do not push through, but have it assessed medically.
Fasting is not an exam you pass. It is a signal your body first has to learn to read again. And learning needs repetition, not harshness.
Shukri Jarmoukli, ViveCura BerlinWhen fasting is not a good idea
This section matters more to me than anything else on this page. There are situations in which a smaller eating window is not a good path, and situations in which it should only take place with medical supervision.
When fasting is not a good idea
- With blood sugar lowering medication: if you take insulin or sulfonylureas, there is an increased risk of hypoglycaemia when fasting. The review by Rajpal and Ismail-Beigi names exactly that for people with type 2 diabetes. In this situation fasting is only justifiable with medical supervision, adapted self-monitoring and, where necessary, adapted medication. Dose changes never in your own hands and never after a blog article.
- With type 1 diabetes: here every change of the eating rhythm strictly belongs in the hands of the treating diabetes team. Grajower and Horne have formulated expert based recommendations on this and emphasise that the evidence base in diabetes is very thin.
- With underweight: a smaller eating window regularly lowers energy intake in the studies. Anyone who already weighs too little needs the opposite.
- With an eating disorder in the history or currently: a large survey by Ganson and colleagues among 2,762 adolescents and young adults in Canada found a significant association between intermittent fasting and eating disorder symptoms in women, men and trans as well as non-binary participants. That is a cross-sectional survey and cannot separate cause from consequence. For me it is enough to advise against it with a corresponding history and to discuss a different approach instead.
- In pregnancy and breastfeeding: the need for nutrients and energy is increased, and controlled data on safety are missing. Not a suitable time for fasting experiments.
- In children and adolescents: growth and development need reliable intake. The clinical studies on intermittent fasting were carried out predominantly in overweight young and middle aged adults, and the NEJM review explicitly records that the results cannot be transferred to other age groups.
- With diuretic medication, low blood pressure or a tendency to dizziness: eating less also means less fluid and less salt. That belongs in a conversation beforehand.
- With warning signs along the way: trembling, palpitations, cold sweat, confusion, visual disturbance or feeling close to fainting are not adjustment phenomena. End the fasting phase, eat, and have it assessed medically promptly.
If you take medication permanently, have a chronic illness or are unsure, please discuss the start personally with a physician beforehand. That is not a formula for covering myself, it is the difference between a sensible change and an avoidable risk.
Three levers for your first week
I deliberately give you no minute by minute plan and no meal prescription here. What suits you depends on your working rhythm, your findings and your medication. What I give you are directions.
Measure before you cut
For one week write down only two times of day: the first bite or sip with calories, and the last. Nothing else. Most people clearly underestimate their eating window, and in the study by Wilkinson and colleagues it was 14 hours and more in the participants. Your real starting value determines how big your first step may be.
Cut in the evening, not in the morning
The data on the early eating window are more consistent than those on the late one. In the study by Jamshed and colleagues the more favourable window lay between 7 am and 3 pm, with Sutton and colleagues it ended before 3 pm, and with Vujović and colleagues late eating went along with more hunger and lower energy expenditure. For the start it is quite enough to bring the last meal forward by an hour and to stay there for two to three weeks.
Plan protein and resistance training in from the start
The difference between the studies by Chow and Moro does not lie in the window, but in everything around it. Without training, fat free mass fell there as well, while with training and enough protein it was maintained. If you shrink a window without looking at the protein amount and the resistance training, you are optimising the wrong half.
The line about starting 16:8 straight away is well meant and still misses the point. It treats an adaptation like a decision. Your metabolism decides nothing. It adapts, and adaptation needs repetition in a tolerable dose.
Ketone bodies begin to rise after 8 to 12 hours. The initial complaints usually disappear within a month. The example scheme in the NEJM review takes four months to reach the goal. All three numbers say the same thing: time is not an obstacle here, it is the mechanism.
You do not have to fast harder. You are allowed to practise longer.
More from the Fasting guide
Read on in the guide
Where this topic connects
Fasting touches metabolism, nervous system, hormonal system and movement at the same time. These articles go deeper into the neighbouring levels.
Blood sugar and insulin resistance
How glucose curves and insulin interact and what that may mean for the rhythm of your day.
MetabolismUnderstanding hunger and satiety
Why hunger gets louder in the first weeks of fasting and which messenger substances are behind it.
NutritionExercise as medicine
What muscle contraction sets off at the cellular level and why resistance training belongs with fasting.
SportBreathing techniques and the vagus nerve
How you can take your foot off the accelerator of the nervous system in restless fasting hours.
Nervous systemFrequently asked questions
How do I best start with intermittent fasting as a beginner?
Why is 16:8 often too much at once for the start?
How long does it take for the body to get used to fasting?
At what point does metabolism switch to fat burning?
Is the morning or the evening the better eating window?
Do you automatically lose weight with intermittent fasting?
Do I lose muscle mass with intermittent fasting?
Should intermittent fasting be judged differently for women?
What may I drink during the fasting window?
Who should not start with intermittent fasting?
What can you do about headaches and irritability in the first days?
Sources
All studies were checked via PubMed against title, authors, year, journal and DOI. Figures come directly from the respective abstracts or full texts and were not converted. The study type is given in square brackets. A note on interpretation: the studies on time restricted eating are predominantly small and short, mostly over 8 to 14 weeks. Large endpoint trials on heart attack, the course of diabetes or life expectancy are so far not available for this dietary form. The stepwise scheme described in this article comes from a review and is an example proposal, not a protocol tested in a study. The statement that a gradual start is superior to a direct start is biologically plausible and is recommended in this way by professional societies and reviews, but it is not established by a direct randomised comparison.
- de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. N Engl J Med. 2019;381(26):2541-2551. DOI: 10.1056/NEJMra1905136 · PMID 31881139 [Review, NEJM review]
- Anton SD, Moehl K, Donahoo WT et al. Flipping the Metabolic Switch: Understanding and Applying the Health Benefits of Fasting. Obesity (Silver Spring). 2018;26(2):254-268. DOI: 10.1002/oby.22065 · PMID 29086496 [Mechanism review]
- 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. DOI: 10.1016/j.cmet.2018.04.010 · PMID 29754952 [RCT, crossover, supervised feeding study]
- Wilkinson MJ, Manoogian ENC, Zadourian A et al. Ten-Hour Time-Restricted Eating Reduces Weight, Blood Pressure, and Atherogenic Lipids in Patients with Metabolic Syndrome. Cell Metab. 2020;31(1):92-104.e5. DOI: 10.1016/j.cmet.2019.11.004 · PMID 31813824 [Real-world, single-arm intervention study, n=19]
- Lowe DA, Wu N, Rohdin-Bibby L et al. Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial. JAMA Intern Med. 2020;180(11):1491-1499. DOI: 10.1001/jamainternmed.2020.4153 · PMID 32986097 [RCT, n=116, 12 weeks]
- Cienfuegos S, Gabel K, Kalam F et al. Effects of 4- and 6-h Time-Restricted Feeding on Weight and Cardiometabolic Health: A Randomized Controlled Trial in Adults with Obesity. Cell Metab. 2020;32(3):366-378.e3. DOI: 10.1016/j.cmet.2020.06.018 · PMID 32673591 [RCT, 8 weeks, adults with obesity]
- Jamshed H, Steger FL, Bryan DR et al. Effectiveness of Early Time-Restricted Eating for Weight Loss, Fat Loss, and Cardiometabolic Health in Adults With Obesity: A Randomized Clinical Trial. JAMA Intern Med. 2022;182(9):953-962. DOI: 10.1001/jamainternmed.2022.3050 · PMID 35939311 [RCT, n=90, 14 weeks]
- Ravussin E, Beyl RA, Poggiogalle E, Hsia DS, Peterson CM. Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans. Obesity (Silver Spring). 2019;27(8):1244-1254. DOI: 10.1002/oby.22518 · PMID 31339000 [RCT, crossover, n=11, metabolic chamber]
- 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. DOI: 10.1016/j.cmet.2022.09.007 · PMID 36198293 [RCT, crossover, strictly controlled]
- Chow LS, Manoogian ENC, Alvear A et al. Time-Restricted Eating Effects on Body Composition and Metabolic Measures in Humans who are Overweight: A Feasibility Study. Obesity (Silver Spring). 2020;28(5):860-869. DOI: 10.1002/oby.22756 · PMID 32270927 [RCT, feasibility study, n=20]
- Moro T, Tinsley G, Bianco A et al. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016;14(1):290. DOI: 10.1186/s12967-016-1044-0 · PMID 27737674 [RCT, n=34, with resistance training]
- Moro T, Tinsley G, Pacelli FQ, Marcolin G, Bianco A, Paoli A. Twelve Months of Time-restricted Eating and Resistance Training Improves Inflammatory Markers and Cardiometabolic Risk Factors. Med Sci Sports Exerc. 2021;53(12):2577-2585. DOI: 10.1249/MSS.0000000000002738 · PMID 34649266 [RCT, n=20, 12 months]
- Varady KA, Cienfuegos S, Ezpeleta M, Gabel K. Cardiometabolic Benefits of Intermittent Fasting. Annu Rev Nutr. 2021;41:333-361. DOI: 10.1146/annurev-nutr-052020-041327 · PMID 34633860 [Review, human studies]
- Manoogian ENC, Chow LS, Taub PR, Laferrère B, Panda S. Time-restricted Eating for the Prevention and Management of Metabolic Diseases. Endocr Rev. 2022;43(2):405-436. DOI: 10.1210/endrev/bnab027 · PMID 34550357 [Mechanism review]
- Goodpaster BH, Sparks LM. Metabolic Flexibility in Health and Disease. Cell Metab. 2017;25(5):1027-1036. DOI: 10.1016/j.cmet.2017.04.015 · PMID 28467922 [Mechanism review]
- Cahill GF Jr. Fuel metabolism in starvation. Annu Rev Nutr. 2006;26:1-22. DOI: 10.1146/annurev.nutr.26.061505.111258 · PMID 16848698 [Review, human physiology]
- Trepanowski JF, Kroeger CM, Barnosky A et al. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med. 2017;177(7):930-938. DOI: 10.1001/jamainternmed.2017.0936 · PMID 28459931 [RCT, n=100, 12 months]
- Gabel K, Hoddy KK, Haggerty N et al. Effects of 8-hour time restricted feeding on body weight and metabolic disease risk factors in obese adults: A pilot study. Nutr Healthy Aging. 2018;4(4):345-353. DOI: 10.3233/NHA-170036 · PMID 29951594 [Real-world, pilot study, n=23]
- Finnell JS, Saul BC, Goldhamer AC, Myers TR. Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complement Altern Med. 2018;18(1):67. DOI: 10.1186/s12906-018-2136-6 · PMID 29458369 [Real-world, chart review of 768 treatment courses]
- Grajower MM, Horne BD. Clinical Management of Intermittent Fasting in Patients with Diabetes Mellitus. Nutrients. 2019;11(4):873. DOI: 10.3390/nu11040873 · PMID 31003482 [Review, expert based recommendation]
- Rajpal A, Ismail-Beigi F. Intermittent fasting and 'metabolic switch': Effects on metabolic syndrome, prediabetes and type 2 diabetes. Diabetes Obes Metab. 2020;22(9):1496-1510. DOI: 10.1111/dom.14080 · PMID 32372521 [Review, safety in diabetes]
- Cienfuegos S, Corapi S, Gabel K et al. Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials. Nutrients. 2022;14(11):2343. DOI: 10.3390/nu14112343 · PMID 35684143 [Review, human studies]
- Ganson KT, Cuccolo K, Hallward L, Nagata JM. Intermittent fasting: Describing engagement and associations with eating disorder behaviors and psychopathology among Canadian adolescents and young adults. Eat Behav. 2022;47:101681. DOI: 10.1016/j.eatbeh.2022.101681 · PMID 36368052 [Real-world, cross-sectional survey, n=2,762]
This article is for information and does not replace medical advice. It describes connections from research and clinical experience, not individual dietary or treatment instructions. If you take medication, in particular insulin or sulfonylureas, if you have diabetes, are pregnant or breastfeeding, are underweight, have an eating disorder in your history or live with a chronic illness, please discuss a change to your eating rhythm personally with a physician beforehand.