Breaking a fast properly: the first meal shapes the whole effect
You held out for 16 hours. Or 24. Or five days. And then you open the window with a bread roll. Why exactly this moment can shape a large part of the result.
Most people invest all their discipline in the hours without food. And then they give away, carelessly, the ten minutes that really offer room to shape things. Fasting is not the pause. Fasting is the pause plus what you do afterwards.
I bet you know this moment. The timer says you may. You stand in front of the fridge, slightly euphoric, slightly light headed, and your body reports only one number: now.
And then you reach for whatever is fastest. A bread roll. A banana. A bowl of muesli. The juice that is already open. Twenty minutes later you are full, pleasantly warm, and an hour after that you sit tired at your desk wondering why you are hungry again.
This is not a character problem. This is physiology. And it is one of the few points in fasting where a small change can make a measurable difference, without you having to go without for longer.
So that you know what you are getting into: the data on food order come from small, controlled studies. None of them was carried out in people who are just ending a fasting period. Each one measured after a normal overnight fast.
The transfer to breaking a fast is physiologically well founded, but it is an inference and not direct evidence. Everything in this article is therefore a reasoned consideration, not a proven rule. I put this at the top rather than in the small print because you should know it while you read.
What awaits you in this article
- What happens in your body while you fast, and what it unlearns
- Why blood sugar can rise particularly steeply after a fasting pause
- The concrete order: what first, what after, with what gap
- Why protein and fat might protect the state you have just reached
- The four KPNI lenses on the moment of breaking a fast
- Refeeding protocols for 16:8, 24 hours and multi-day fasting
- Refeeding syndrome: placed in context, without scaremongering
- Three levers you can put into practice tomorrow morning
What happens inside you while you fast
Imagine your metabolic system as a house with two heating systems. One runs on glucose, fast and convenient. The other runs on fatty acids and ketone bodies, slower, but with a huge tank in the basement.
As long as you eat regularly, the fast heating stays on. It is never switched off entirely, so the house never really learns to operate the second one. Fasting is, at its core, nothing other than the moment when the first heating goes out and the second one has to start up.
A research group around Anton compiled in 2018 in Obesity when this switching point occurs in physiology. They describe it as the point of negative energy balance at which the glycogen stores of the liver are depleted and fatty acids are mobilised, typically beyond twelve hours after the last food intake.
What that means for you: everything you do before hour twelve is a break from eating. Everything after it is a different biochemical situation. And the further you go into that situation, the more your body has adapted, which it also has to reverse when you come back in.
Anton SD et al. Obesity (Silver Spring). 2018. DOI: 10.1002/oby.22065A lot happens at once during this changeover. Insulin drops to a very low level. Glucagon rises. The pancreas can provide fewer digestive enzymes, because there is nothing to digest right now. Gastric emptying and the transport activity of the intestinal lining can adapt as well.
Much of this we know above all from investigations of longer food deprivation and from animal models. For a 16 hour window it is a plausible inference, not a measured finding. I mention it anyway, because it describes the setting your first meal lands in.
All of this makes sense. It is an adaptation, not a defect. But it also means: the apparatus your first meal meets is not the same one as yesterday at lunchtime.
You are not eating into the same body you got up with in the morning. You are eating into a body that has just rebuilt itself. And that rebuilding is exactly the reason you fasted in the first place.
What fasting actually did in studies
Before we talk about breaking it, a brief word on what this is all about. Because there is a lot of euphoria circulating, and honest science is more differentiated at this point.
Sutton and colleagues carried out in 2018 in Cell Metabolism the first controlled feeding study in which men with prediabetes were given enough to eat for their weight to stay constant. For five weeks they ate within a six hour window with dinner before 3 pm, and alternately within a twelve hour window.
What was observed were improvements in insulin sensitivity, beta cell responsiveness, blood pressure, oxidative stress and appetite. And this without weight loss. That is the genuinely interesting point: the effect did not hang on the kilos alone.
Sutton EF et al. Cell Metab. 2018;27(6):1212-1221.e3. DOI: 10.1016/j.cmet.2018.04.010An umbrella review in JAMA Network Open summarised in 2021 eleven meta-analyses with a total of 130 randomized trials and assessed 104 individual associations between intermittent fasting and health parameters. 28 of them were statistically significant. But only a single one was supported by high quality evidence.
And a meta-analysis in Advances in Nutrition with 28 studies found no advantage of intermittent fasting over continuous calorie reduction for body weight. So fasting is not magic. It is a tool that is more practicable for some people than daily counting, and one that addresses certain metabolic pathways. It does not need a bigger claim than that.
If part of the benefit hangs on insulin sensitivity and on the calm of your blood sugar curve, then the first meal is not the end of the fast. It is the last, most active part of it. You are not closing the door. You are deciding how you close it.
The most common mistake: opening the window with carbohydrates
May I ask you an uncomfortable question? What was the first thing you ate last time you opened your eating window?
With most people I speak to, the answer is something starchy or something sweet. Bread, fruit, oats, rice, a smoothie, a bar on the way. There are good reasons for that. The body is calling for rapidly available energy, and carbohydrates are the fastest answer there is.
Only this fast answer meets a digestive tract that is on receive as rarely otherwise. The stomach is empty. There is no food pulp buffering the uptake. Gastric emptying has little to slow down. And the pancreas has to ramp up within a second from a very low baseline insulin level.
This can lead to a blood sugar curve that does not rise, it jumps. And what follows is often an equally strong drop.
This has so far been measured after a normal overnight fast, not after a long fast. So it is a reasoned assumption, not a measured value.
Why peaks are more relevant than average values
Here a study comes into play that I consider one of the most instructive in all of metabolic medicine.
Monnier and colleagues compared in 2006 in JAMA 21 people with type 2 diabetes with 21 control subjects. They measured oxidative stress via the urinary excretion of 8-iso-prostaglandin F2alpha and set this against blood sugar data from continuous glucose monitoring.
What was observed: the excretion rate was 482 versus 275 picograms per milligram of creatinine in the people with diabetes. And the strongest association was not with the long term value HbA1c, but with the mean amplitude of blood sugar fluctuations. The authors concluded that acute blood sugar fluctuations may represent a more specific trigger for oxidative stress than persistently elevated values.
What that means for you: not only how high your sugar is on average, but how strongly it jumps back and forth, might play a biological role. And in many people who fast, the steepest curve of the day is precisely the first meal.
Monnier L et al. JAMA. 2006;295(14):1681-1687. DOI: 10.1001/jama.295.14.1681This investigation was carried out in people with type 2 diabetes, not in healthy people who fast. I cannot conclude from it that a single steep curve is harmful for you. What I can conclude: the assumption that the range of fluctuation may have a biological meaning of its own is well founded. It is an argument for calm, not for fear.
"Fasting trains your body to manage without a constant supply. If you then open the window with the steepest curve of the day, you send two opposing signals into the same metabolism."
Shukri Jarmoukli, ViveCura BerlinThe order logic: what first, what after, with what gap
Now comes the part that excites me most as a physician. Because here there really are clean data, and they say something surprisingly practical.
The research question was simple: what happens when the same meal with the same calories and the same nutrients is eaten in a different order? Not different foods. Not less. Only a different sequence on the plate.
Shukla and colleagues had fifteen people with prediabetes eat the same meal on three days in 2018 in Diabetes, Obesity and Metabolism, each time in a different order: carbohydrates first, then protein and vegetables ten minutes later. Or protein and vegetables first, carbohydrates ten minutes later. Or vegetables first, then protein and carbohydrates.
What was observed: the blood sugar peaks in both variants with carbohydrates last were more than 40 percent lower than with carbohydrates first. The area under the glucose curve was 38.8 percent lower with protein and vegetables first. And while the curve with carbohydrates first fluctuated markedly, it stayed stable in the other two variants.
What that means for you: ten minutes of spacing and a deliberate order could have an effect that otherwise only a substantial reduction in portion size achieves.
Shukla AP et al. Diabetes Obes Metab. 2019;21(2):377-381. DOI: 10.1111/dom.13503The PATTERN study around Sun examined in 2019 in Clinical Nutrition whether this effect also occurs in healthy people. Sixteen healthy Chinese adults in Singapore ate five isocaloric meals of vegetables, chicken breast and white rice in five different orders, that is a typically Asian meal.
What was observed: compared with rice first, the blood sugar response was clearly attenuated in all other orders. With vegetables, then meat, then rice, the insulin area in the first hour was additionally lower than in most of the other variants, and GLP-1 release the highest. So less blood sugar with less insulin needed.
What that means for you: you do not need a metabolic disease for the order to change something. It can change something in healthy people too. How well an Asian rice meal transfers to a European plate remains an open question.
Sun L et al. Clin Nutr. 2020;39(3):950-957, published online ahead of print 2019. DOI: 10.1016/j.clnu.2019.04.001Shaheen and colleagues had eighteen healthy adults in the United Arab Emirates eat two isocaloric meals in 2024: once as a standard mixed meal, once with vegetables and protein first and carbohydrates afterwards.
What was observed: the glucose area over two hours was 40.9 percent lower in the variant with carbohydrates last, the insulin area 31.7 percent lower. The feeling of fullness was higher at two single time points, after 60 and after 120 minutes, both just at the threshold of significance. Across the whole course there was no difference in hunger rating.
What that means for you: the order might influence not only the curve, but perhaps also how long you stay full. I read this hint carefully, because it only showed at single time points. It stays interesting nonetheless, because breaking a fast is where most people go back for seconds.
Shaheen A et al. Diabetes Metab Syndr Obes. 2024;17:4257-4265. DOI: 10.2147/DMSO.S468628A Japanese investigation by Nishino arrived at the same picture in 2018: eight healthy young adults ate rice, vegetables and meat in three different orders. The areas under the glucose and the insulin curve over 120 minutes were smallest when the rice came last, and largest when it came first.
And a review by Astbury in Diabetes, Obesity and Metabolism now explicitly counts the food order vegetables before protein before carbohydrates among the simple strategies that come into question for dampening the blood sugar peak after eating.
The order translated onto your plate
First liquid and fibre
A warm vegetable or bone broth, a small salad, steamed vegetables. Warm is often more pleasant than cold. There are no robust studies on this, it is experience from the fasting tradition and from my practice. The fibre can let what comes afterwards pass through the stomach more slowly.
Minute 0 to 5Then protein
Eggs, meat, poultry, organ meats, a plain yoghurt or quark if you tolerate dairy. Protein can slow gastric emptying considerably and can stimulate the satiating gut hormones GLP-1 and peptide YY. Fat works in the same direction. Which of the two effects is stronger in an individual case depends on amount and composition.
Minute 5 to 15Then fat
Olive oil, avocado, butter or ghee, a high quality omega-3 oil or algae oil. Fat can slow gastric emptying further and can improve the uptake of fat soluble vitamins from the vegetables.
together with step 2Only then starch or sweet foods
Potatoes, rice, bread, fruit. If you want them, eat them. But at the end, into a digestion that is already filled and slowed. With short fasts on the same day, with multi-day fasting rather on the following one. One important exception is in the box directly below this overview.
at the endYou are allowed to eat carbohydrates. Only afterwards and not before. There is one important exception, though. If you inject insulin or take a blood sugar lowering medication such as a sulfonylurea, the time gap between the medication and the carbohydrates is part of how your therapy is set. If you move the carbohydrates later on your own, a severe hypoglycaemia can result.
So discuss any change of the order beforehand with the physician who manages your therapy. All the food order studies cited here were carried out in people without insulin therapy, mostly in diet controlled or healthy participants. They do not transfer readily to an ongoing insulin or sulfonylurea therapy.
Carbohydrates remain part of the meal. In all the studies cited, exactly the same amount was eaten, only in a different sequence. That is precisely what makes this recommendation so usable in everyday life: it costs you nothing. No going without, no money, no additional discipline. Only a different order on a plate that is in front of you anyway. And now you know why.
Why protein and fat might protect the state you have reached
Let us stay with protein for a moment, because here the data are particularly clean and the mechanism particularly easy to follow.
When protein arrives in the stomach, a chain of things happens. The stomach empties more slowly. Amino acids reach the small intestine, where GLP-1 and GIP are released, the so called incretins. These hormones tell the pancreas: food is on its way, get ready. And they tell the brain: something is arriving, you can wind down.
Ma and colleagues examined in 2015 in Diabetes Research and Clinical Practice whether a small amount of protein before the meal retains its effect when taken regularly over weeks. People with diet controlled type 2 diabetes received 25 grams of whey protein as a preload.
What was observed: the ability of this preload to slow gastric emptying and to lower blood sugar after the meal persisted even after four weeks of regular intake. So the body did not get used to it.
What that means for you: this is not a one off trick, but a strategy that can be repeated.
Ma J et al. Diabetes Res Clin Pract. 2015;108(2):e31-e34. DOI: 10.1016/j.diabres.2015.02.019Particularly important for our topic is a detail from a review by Smith in Frontiers in Nutrition: the size of the effect appears to be greater when the protein is eaten before the meal rather than together with it. That is exactly the order logic, only in a different study design.
And what does that do to your hunger?
This is where it gets interesting, because breaking a fast rarely stays with one meal. The rest of the eating window is co-determined by what you opened it with.
Leidy and colleagues studied in 2013 in the American Journal of Clinical Nutrition twenty young women with overweight, on average 19 years old, who usually skip breakfast. Over six days they received either a breakfast with 13 grams of protein, one with 35 grams of protein from egg and beef, or none at all.
What was observed: only the protein rich variant lowered ghrelin over the day, raised peptide YY and reduced evening snacking on high fat foods. Imaging additionally showed lower activation in brain areas that respond to food cues.
What that means for you: the first meal might co-determine how much food still occupies you six or eight hours later.
Leidy HJ et al. Am J Clin Nutr. 2013;97(4):677-688. DOI: 10.3945/ajcn.112.053116Jakubowicz and colleagues compared in 2012 in Steroids a low carbohydrate breakfast with a breakfast rich in carbohydrates and protein in 193 people with obesity. After the breakfast rich in protein and carbohydrates, ghrelin fell by 45.2 percent, after the low carbohydrate one by only 29.5 percent. The group with the larger breakfast also maintained their weight better.
That is not an argument against the order, but it is an argument against dogmatism. It shows that the amount of protein in the first meal apparently plays a role of its own, independent of whatever else is on the plate. What I take from it: plenty of protein first is the most robust part of the recommendation. Whether you eat carbohydrates afterwards is a second, more individual question.
Four lenses on the same moment
In Clinical Psychoneuroimmunology we look at every event through four windows at the same time. Breaking a fast is a nice example, because all four have something to say at once.
Nervous system
Fasting pushes you towards the sympathetic side, meaning alertness and focus. Digestion needs the opposite: the parasympathetic side. If you eat standing, walking or in front of a screen, the switch stays off. That is why sitting down, smelling, chewing slowly is not a wellness gesture. It is the start button for saliva, stomach acid and pancreatic secretion.
Immune system
The largest part of your immune cells sits around the gut. After a fasting pause the mucosa is in a different state, and a large, heavily processed meal meets a system that was just downregulated. A gentle, well chewed start can spare this interface.
Metabolism
Insulin is at a low point, the liver has switched to ketone production, fat burning is running. A steep carbohydrate stimulus can end this state abruptly. A start centred on protein and fat ends it too, but probably more softly and over a longer period.
Hormonal system
Ghrelin, GLP-1, peptide YY and cortisol respond within minutes to what arrives. The first meal may therefore set not only a blood sugar value, but a hormonal baseline melody for the next few hours. That is exactly why it can shape more than itself.
"The body does not regulate itself in separate parts, and it does not eat in separate parts either. A meal is always at the same time a nervous, an immune, a metabolic and a hormonal event."
Shukri Jarmoukli, ViveCura BerlinRefeeding protocols: 16:8, 24 hours, multi-day
The longer you have fasted, the more your body has adapted, and the more gently the way back should be shaped. That is the only rule you have to remember. Everything else follows from it.
16:8 and similar short windows
- A normal meal is fine, no refeeding phase needed
- Mind the order: vegetables, then protein and fat, then starch
- A realistic portion instead of catching up on missed calories
- Eat slowly, at least 20 minutes for the first meal
- Drinks without sugar, no juice as the opening
20 to 36 hours
- First a small warm broth or steamed vegetables
- After about 30 to 60 minutes a small protein meal
- Portion size about half of a usual meal
- Starch and sweet foods only with the second meal of the day
- Mind enough fluid and salt, especially with headache
- Potassium and magnesium supplements not on your own, only after talking to a physician
Several days
- Belongs in medical care as a matter of principle, refeeding included
- Rule of thumb: about one refeeding day per three to four fasting days
- Start with very small, soft, warm portions
- Increase carbohydrates slowly over several days, not on the first day
- Electrolytes and vitamin B1 belong in the plan, not left to chance
These are directions, not recipes. I deliberately give no gram and calorie figures here, because the appropriate amount depends on how long you fasted, how you started, which medications you take and what your lab values say. Anyone taking diabetes medication, blood pressure medication, diuretics or anticoagulants should plan fasting and breaking a fast exclusively in coordination with their physician.
Insulin and sulfonylureas. The time gap between the medication and the carbohydrates is part of how the therapy is set. Anyone who moves the carbohydrates later on their own can trigger a severe hypoglycaemia. A change like that belongs in a conversation with a physician beforehand.
SGLT2 inhibitors. Under this prescription only class of drugs, fasting can trigger a so called euglycaemic ketoacidosis, meaning a dangerous acidification of the blood at an almost normal blood sugar level. This is rare, but potentially life threatening and hard for those affected to recognise, because the glucose meter stays unremarkable. Please do not fast without medical coordination.
Potassium and magnesium. These supplements are available without prescription, but they are not harmless. With impaired kidney function and under blood pressure medication such as ACE inhibitors, sartans or potassium sparing diuretics, additional potassium can lead to a dangerous overload of the blood. So take them only after talking to a physician.
Children and adolescents. Intermittent fasting and multi-day fasting are not suitable for minors. During growth and development an energy deficit is a different matter than in adults, and strict eating rules can set off disordered eating at that age.
Pregnancy and breastfeeding. I advise against multi-day fasting during this time. Longer gaps between meals also belong in a conversation with a physician beforehand.
Underweight and eating disorders. With a body mass index below 18.5 and with a current or past eating disorder, fasting is not a suitable method. If this concerns you: in Germany the eating disorder helpline of the Federal Centre for Health Education can be reached on 0221 892031. Outside those hours the medical on call service is available on 116 117, and in an acute emergency the number is 112.
What the classical fasting tradition says about it
In the Buchinger tradition, breaking a fast classically begins with an apple. Strictly speaking that is carbohydrate first, so the opposite of what I described above. I find this contradiction interesting enough not to talk it away.
The apple has a logic of its own: tiny amount, long chewing, plenty of pectin as fibre, very low total load. The gesture is ritual and signal more than nutrient supply. And supervised fasting therapy according to Buchinger is one of the best documented forms of longer fasting there is.
Wilhelmi de Toledo and colleagues documented in 2019 in PLoS One 1422 people over the course of a year who fasted between 4 and 21 days in a specialised clinic, with 200 to 250 kilocalories daily and an accompanying exercise programme.
What was observed were reductions in weight, waist circumference and blood pressure, a rise in ketone bodies as evidence of the metabolic switch, and improvements in blood lipids and blood sugar regulation. 93.2 percent reported no feeling of hunger. Of the 404 participants with pre-existing complaints, 341, that is 84.4 percent, reported an improvement. Adverse effects were documented in fewer than one percent of participants.
This figure needs context: it comes from an observational study without a control group, in a specialised clinic, in people who had chosen it for themselves and were looked after daily. It says something about supervised fasting in that setting. It does not transfer to fasting on your own.
What that means for you: longer fasting can be tolerable within a structured, medically supervised setting. The word "supervised" is not a detail here, it is the condition.
Wilhelmi de Toledo F et al. PLoS One. 2019;14(1):e0209353. DOI: 10.1371/journal.pone.0209353The fasting tradition looks at amount, pace and mindfulness. Metabolic research looks at the order of the macronutrients. Both lenses aim at the same thing: keeping the load small for a downregulated system. I consider it sensible to combine the two rather than to play one off against the other.
Refeeding syndrome: the safety topic without scaremongering
Now to the point where the internet either says nothing at all or goes straight to fear. I think both are wrong.
Refeeding syndrome is real, it is well described, and it is serious. But it concerns a clearly defined group of people and not everyone who skips a breakfast.
What happens in it
During a longer period without food, the body shifts minerals from the cells into the blood in order to keep blood levels stable. The blood values for phosphate, potassium and magnesium then look normal, although the body's total stores are already depleted. It is like an account that still shows a balance because the reserve keeps topping it up.
If calories now arrive suddenly, above all carbohydrates, insulin rises. Insulin pushes glucose, phosphate, potassium and magnesium back into the cells together. The blood levels of these minerals can drop rapidly in the process. And phosphate is the raw material for ATP, meaning the energy currency of every cell, including heart muscle, respiratory muscles and nerves.
The American society for parenteral and enteral nutrition published a consensus definition in 2020. It classifies a drop in serum phosphate, potassium or magnesium by 10 to 20 percent as mild, by 20 to 30 percent as moderate, and above 30 percent or with resulting organ dysfunction as severe. What matters is that it occurs within five days of restarting calorie intake. Thiamine deficiency is explicitly included.
da Silva JSV et al. Nutr Clin Pract. 2020;35(2):178-195. DOI: 10.1002/ncp.10474Heuft and colleagues summarised in 2023 in Deutsches Ärzteblatt why refeeding syndrome is so hard to recognise clinically: the symptoms are unspecific and awareness of the risk is often low.
What was observed in the literature reviewed: malnourished patients with refeeding syndrome had a higher mortality after six months with an odds ratio of 1.54, and a higher risk of intensive care admission with an odds ratio of 2.71.
What that means for you: this is a hospital topic in malnutrition, not a topic for your 16:8. But it is the reason why multi-day fasting belongs in medical care.
Heuft L et al. Dtsch Arztebl Int. 2023;120(7):107-114. DOI: 10.3238/arztebl.m2022.0381Who this is relevant for
An increased risk exists among others with
- Marked underweight: a low body mass index at the start of nutrition is, in investigations, a better predictor of a phosphate drop than the calorie amount itself.
- Eating disorders: anorexia nervosa and related conditions, also after a longer period of stability.
- Unintentional weight loss: more than about ten percent of body weight in recent months without intending it.
- Very low food intake over days: regardless of whether deliberate or caused by illness.
- Alcohol dependence: here thiamine deficiency comes in as a risk of its own.
- Chronic bowel disease: when nutrient absorption is impaired anyway.
- Certain medications: above all diuretics, insulin, chemotherapies and antacids.
- Advanced age with frailty: because the reserves are smaller and the distances shorter.
If you are healthy, of normal weight, none of the situations listed above applies to you and you fast for 16 or 24 hours, refeeding syndrome is not a realistic scenario. I write about it so that you know the boundary, not so that you fear it.
If, however, even one of the points applies to you, or if you want to fast for longer than about 48 hours, then discuss it with a physician beforehand. Not during. Beforehand.
A systematic review by Mosuka evaluated twenty papers in 2023 with a total of 2191 children and adolescents who were fed as inpatients because of anorexia nervosa. In only a single one of these twenty papers was there an actual clinical case of refeeding syndrome. The traditional rule "start low and go slow" is therefore being discussed increasingly in the field.
Important for understanding this: all of these children and adolescents were fed as inpatients, with daily laboratory monitoring and medical steering. That supervision is presumably the reason for the low number. It is expressly not an all clear for refeeding on your own. With a current or past eating disorder, fasting is not a suitable method.
I cite this because I do not want to tell a one sided fear story. The message is not "dangerous". The message is: in risk constellations, laboratory monitoring and supervision are part of it, and then refeeding is as a rule well manageable.
Three levers you can put into practice next time
I do not like lists with twenty points. You will remember three, so I name three.
1. Turn the plate around
Eat the same meal you were going to eat anyway, only in this order: vegetables or broth, then protein and fat, then starch. Let a few minutes pass between protein and side dish. In the studies, ten were enough. If you take insulin or another blood sugar lowering medication, do not change the order without talking to a physician.
2. Halve the first portion
Not the daily amount, only the first portion. What you eat in the first twenty minutes decides the steepest curve. If you are still hungry afterwards, eat more. That is allowed and usually not even necessary.
3. Sit down and chew
Digestion needs the parasympathetic side. Sitting, smelling, chewing slowly, not on the side in front of a screen. This is the only one of the three measures that has nothing to do with nutrition at all, and for many the most effective.
And if you have fasted for longer
From about 24 hours: start warm, start small, move carbohydrates to the following day. From several days: do not plan it alone. That is not a cautionary phrase, it is a medical recommendation.
Fasting is not the art of eating nothing. Fasting is the art of shaping the transition. Your body handles the pause on its own. The transition is yours.
And that is, in the end, the point that really interests me about this topic. It is not about a few percent of blood sugar area. It is about not feeling tired and empty after eating, but clear. About not thinking of food again two hours later. About your afternoon belonging to you and not to your digestion.
Energy is not a luxury. Energy is the difference between a day you shape and a day you get through. And part of it is decided in ten minutes that you have probably never paid attention to. And now you know why.
Where this topic also comes into play
Breaking a fast does not stand on its own. It touches blood sugar regulation, the nervous system, the intestinal lining and the hormonal balance at the same time. You will find further articles on these connections gathered in the fasting section.
Breaking a fast
The first meal and its order
this articleFasting Guide
All articles on fasting formats, effects and practice
Blood sugar
Insulin sensitivity, glucose peaks, a calm curve
Gut
Mucosa, enzymes and digestion after the pause
Frequently asked questions about breaking a fast
How do I break a fast properly?
Start small, chew slowly and mind the order. It makes sense to begin with some vegetables or a warm broth, then to eat a well tolerated protein source together with a high quality fat, and to add starchy or sweet foods only at the end.
Studies on so called food order show that carbohydrates last can flatten the blood sugar peak considerably, with an identical amount of nutrients. In Shukla's study the peak was more than 40 percent lower when protein and vegetables came first. That was measured after a normal overnight fast, not after a fasting period.
The longer the fast was, the more careful the refeeding should be. After 16 hours a normal, deliberately ordered meal is enough. After several days, a structured refeeding phase over several days in medical care is needed.
If you inject insulin or take another blood sugar lowering medication, please do not change the order on your own, but discuss it with a physician beforehand.
Why should I not open the eating window with carbohydrates?
Because your digestive tract is maximally ready to absorb at this moment. The stomach is empty, there is no food pulp slowing the passage, and the pancreas has to respond from a very low insulin level.
Rapidly available carbohydrates can therefore trigger a particularly steep blood sugar and insulin response. In controlled investigations the curve after carbohydrates first was clearly more restless than after vegetables and protein first.
On top of that comes the practical effect: the subsequent drop often shows up as tiredness and renewed cravings, which can co-determine the rest of the eating window.
What is the best first meal after 16 hours of fasting?
After 16 hours the digestive tract as a rule tolerates a completely normal meal. No refeeding phase is needed.
A combination centred on protein and fat works well: eggs with steamed vegetables and olive oil, meat or poultry with salad, quark or plain yoghurt with nuts if you tolerate dairy. A high quality omega-3 oil or algae oil goes well with it.
You are allowed to eat carbohydrates. Only afterwards and not before. And eat a realistic portion instead of catching up on the missed calories in one sitting.
One important exception: if you inject insulin or take a blood sugar lowering medication such as a sulfonylurea, the time gap between the medication and the carbohydrates is part of how your therapy is set. In that case do not move the carbohydrates on your own, but discuss the order beforehand with the physician who manages your therapy.
How long do the refeeding days after a multi-day fast last?
As a rule of thumb, the fasting tradition suggests about one refeeding day per three to four fasting days, but at least two to three days. During this time amount, energy density and carbohydrate share are increased step by step.
In practice this means: very small, soft, warm portions at the beginning, several small meals instead of a few large ones, and starch in relevant amounts only after the first one to two days.
For fasting periods lasting several days the refeeding phase belongs in medical care. In this phase shifts of phosphate, potassium and magnesium can occur. They are not the rule, but they are the reason to look closely during this time and to check the values if in doubt.
What is refeeding syndrome?
Refeeding syndrome is a metabolic derailment that can occur when a body that has been undernourished or fasting for a long time receives calories again, especially in the form of carbohydrates.
Insulin rises, and phosphate, potassium and magnesium move rapidly from the blood into the cells together with glucose. Since phosphate is the raw material for ATP, a strong drop can affect the heart, the respiratory muscles and the nervous system.
The ASPEN consensus recommendations define a drop of these electrolytes by 10 to 20 percent as mild, by 20 to 30 percent as moderate and above 30 percent or with organ dysfunction as severe, when it occurs within five days of restarting calorie intake.
Who is at increased risk of refeeding syndrome?
Affected are above all people who are markedly underweight, who have eating disorders, unintentional weight loss, alcohol dependence, a long period of very low food intake, chronic bowel disease with impaired absorption, or who take medications such as diuretics, insulin or chemotherapies.
A low body mass index at the start of refeeding was, in analyses, a better predictor of a phosphate drop than the amount of calories supplied itself.
A healthy person of normal weight without the risk factors listed above who fasts for 16 or 24 hours does not as a rule belong to this group. For multi-day fasting and for any relevant pre-existing condition the assessment should be made by a physician beforehand.
Is an apple the wrong way to break a fast?
No, it is not wrong. The apple is the classic opening of the Buchinger fasting tradition and has a logic of its own that makes sense: small amount, slow chewing, plenty of pectin as fibre, very low total load. It is ritual and signal more than nutrient supply.
The newer data on food order do suggest, however, that an opening centred on protein and fat might keep the blood sugar curve calmer. Both approaches aim at the same thing, namely a small load for a downregulated system.
What matters in the end is amount, pace and what follows in the hours afterwards. An apple as the first bite is unproblematic. A large plate of pasta as the first meal after five days of fasting is something else.
How much time should pass between the components?
In the studies on food order, carbohydrates were typically eaten ten minutes after vegetables and protein. Even this short gap was enough for a clear difference in blood sugar and insulin.
In practice this means: you need neither separate meals nor a timer. It is enough to clear the plate in a deliberate order and to let a few minutes pass between protein and side dish.
If you eat in stages after a longer fast, the gap may be larger, for example 30 to 60 minutes between broth and the first solid meal.
The exception for insulin and other blood sugar lowering medication applies here too: any shifting of the carbohydrates belongs in a conversation with a physician beforehand.
Why am I sometimes tired or shaky after breaking a fast?
A very steep blood sugar peak is often accompanied by an equally strong insulin response. The subsequent drop can show up as tiredness, shakiness, loss of concentration or renewed cravings.
There is also a circulatory effect: after a large meal, blood is redistributed into the digestive tract, which can briefly lower blood pressure. After a fasting phase with already lower blood pressure this is more noticeable.
A smaller first portion, a slower pace, carbohydrates at the end and enough salt and fluid can ease this reaction. If complaints occur repeatedly or are pronounced, that belongs in medical assessment.
One important difference: anyone taking insulin or a blood sugar lowering medication has to think of a genuine hypoglycaemia first when shakiness, sweating and palpitations occur. Then the opposite of the advice above applies: measure blood sugar and eat fast carbohydrates immediately. With confusion, clouded consciousness or a seizure this is an emergency, and the emergency number should be called at once, which is 112 in Germany and across the EU.
Do I lose the benefit of fasting if I break it the wrong way?
No, the benefit does not disappear because of a single meal. Fasting is more robust than that.
But part of what makes fasting interesting in studies concerns precisely insulin sensitivity and the calm of the blood sugar curve. In Sutton's investigation these parameters improved even without any weight loss. Anyone who regularly opens the window with a large, rapidly available amount of carbohydrates is working against their own goal on this point.
The good news is how simple the correction is. It costs neither going without nor money nor additional discipline. Only a different order on a plate that is in front of you anyway.
Scientific sources
All sources were checked via PubMed for existence, authorship, journal and year, and the figures named in the text come from the respective abstract. The study type is given in square brackets so that you can judge the robustness yourself.
- Shukla AP, Dickison M, Coughlin N et al. The impact of food order on postprandial glycaemic excursions in prediabetes. Diabetes Obes Metab. 2019;21(2):377-381. DOI: 10.1111/dom.13503 [Controlled feeding study with randomized order, crossover, n=15, prediabetes]
- Sun L, Goh HJ, Govindharajulu P et al. Postprandial glucose, insulin and incretin responses differ by test meal macronutrient ingestion sequence (PATTERN study). Clin Nutr. 2020;39(3):950-957, published online ahead of print 2019. DOI: 10.1016/j.clnu.2019.04.001 [RCT, crossover, n=16, healthy Chinese adults in Singapore]
- Shaheen A, Sadiya A, Mussa BM, Abusnana S. Postprandial Glucose and Insulin Response to Meal Sequence Among Healthy UAE Adults: A Randomized Controlled Crossover Trial. Diabetes Metab Syndr Obes. 2024;17:4257-4265. DOI: 10.2147/DMSO.S468628 [RCT, crossover, n=18]
- Nishino K, Sakurai M, Takeshita Y, Takamura T. Consuming Carbohydrates after Meat or Vegetables Lowers Postprandial Excursions of Glucose and Insulin in Nondiabetic Subjects. J Nutr Sci Vitaminol (Tokyo). 2018;64(5):316-320. DOI: 10.3177/jnsv.64.316 [Controlled crossover study, n=8]
- Astbury NM. Interventions to improve glycaemic control in people living with, and at risk of developing type 2 diabetes. Diabetes Obes Metab. 2024;26 Suppl 4:39-49. DOI: 10.1111/dom.15855 [Review]
- Ma J, Jesudason DR, Stevens JE et al. Sustained effects of a protein preload on glycaemia and gastric emptying over 4 weeks in patients with type 2 diabetes: A randomized clinical trial. Diabetes Res Clin Pract. 2015;108(2):e31-e34. DOI: 10.1016/j.diabres.2015.02.019 [RCT, crossover, type 2 diabetes]
- Smith K, Bowden Davies KA, Stevenson EJ, West DJ. The Clinical Application of Mealtime Whey Protein for the Treatment of Postprandial Hyperglycaemia for People With Type 2 Diabetes. Front Nutr. 2020;7:587843. DOI: 10.3389/fnut.2020.587843 [Review]
- Mignone LE, Wu T, Horowitz M, Rayner CK. Whey protein: The whey forward for treatment of type 2 diabetes? World J Diabetes. 2015;6(14):1274-1284. DOI: 10.4239/wjd.v6.i14.1274 [Mechanism review]
- Pham H, Holen IS, Phillips LK et al. The Effects of a Whey Protein and Guar Gum-Containing Preload on Gastric Emptying, Glycaemia, Small Intestinal Absorption and Blood Pressure in Healthy Older Subjects. Nutrients. 2019;11(11):2666. DOI: 10.3390/nu11112666 [Human study, n=18, older adults]
- Monnier L, Mas E, Ginet C et al. Activation of oxidative stress by acute glucose fluctuations compared with sustained chronic hyperglycemia in patients with type 2 diabetes. JAMA. 2006;295(14):1681-1687. DOI: 10.1001/jama.295.14.1681 [Case-control study, n=42]
- Sutton EF, Beyl R, Early KS et al. 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 [Controlled clinical trial, crossover]
- 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 [Mechanism review]
- Wilhelmi de Toledo F, Grundler F, Bergouignan A, Drinda S, Michalsen A. Safety, health improvement and well-being during a 4 to 21-day fasting period in an observational study including 1422 subjects. PLoS One. 2019;14(1):e0209353. DOI: 10.1371/journal.pone.0209353 [Prospective observational study, n=1422]
- Patikorn C, Roubal K, Veettil SK et al. Intermittent Fasting and Obesity-Related Health Outcomes: An Umbrella Review of Meta-analyses of Randomized Clinical Trials. JAMA Netw Open. 2021;4(12):e2139558. DOI: 10.1001/jamanetworkopen.2021.39558 [Systematic review, 11 meta-analyses, 130 RCTs]
- Schroor MM, Joris PJ, Plat J, Mensink RP. Effects of Intermittent Energy Restriction Compared with Those of Continuous Energy Restriction on Body Composition and Cardiometabolic Risk Markers. Adv Nutr. 2024;15(1):100130. DOI: 10.1016/j.advnut.2023.10.003 [Meta-analysis, k=28 RCTs]
- Mehanna HM, Moledina J, Travis J. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ. 2008;336(7659):1495-1498. DOI: 10.1136/bmj.a301 [Review]
- da Silva JSV, Seres DS, Sabino K et al. ASPEN Consensus Recommendations for Refeeding Syndrome. Nutr Clin Pract. 2020;35(2):178-195. DOI: 10.1002/ncp.10474 [Review, consensus recommendation]
- Heuft L, Voigt J, Selig L, Stumvoll M, Schlögl H, Kaiser T. Refeeding Syndrome. Dtsch Arztebl Int. 2023;120(7):107-114. DOI: 10.3238/arztebl.m2022.0381 [Review]
- Mosuka EM, Murugan A, Thakral A et al. Clinical Outcomes of Refeeding Syndrome: A Systematic Review of High vs. Low-Calorie Diets for the Treatment of Anorexia Nervosa and Related Eating Disorders in Children and Adolescents. Cureus. 2023;15(5):e39313. DOI: 10.7759/cureus.39313 [Systematic review, k=20, n=2191]
- Leidy HJ, Ortinau LC, Douglas SM, Hoertel HA. Beneficial effects of a higher-protein breakfast on the appetitive, hormonal, and neural signals controlling energy intake regulation in overweight/obese, breakfast-skipping, late-adolescent girls. Am J Clin Nutr. 2013;97(4):677-688. DOI: 10.3945/ajcn.112.053116 [RCT, crossover, n=20]
- Jakubowicz D, Froy O, Wainstein J, Boaz M. Meal timing and composition influence ghrelin levels, appetite scores and weight loss maintenance in overweight and obese adults. Steroids. 2012;77(4):323-331. DOI: 10.1016/j.steroids.2011.12.006 [RCT, n=193]
Transparency on the evidence. The data on food order come from small but controlled studies with mostly 8 to 20 participants and short observation periods. They show consistent effects on blood sugar and insulin after a single meal. Whether this translates over years into an advantage for hard health outcomes has not so far been tested in large long term studies. None of the investigations cited was carried out specifically in people taking their first meal after a fasting period. The transfer to this situation is physiologically well founded, but it is an inference and not direct evidence.
No substitute for medical advice. This article serves as information and does not replace an individual medical examination, diagnosis or treatment. Anyone who takes medication, is pregnant or breastfeeding, has or has had an eating disorder, has diabetes, kidney, liver or heart disease, or wants to fast for longer than 24 hours should discuss the approach with a physician beforehand.
Where I clearly advise against it. For children and adolescents, during pregnancy and breastfeeding, with a body mass index below 18.5 and with a current or past eating disorder, multi-day fasting is not suitable. For eating disorders in Germany, the helpline of the Federal Centre for Health Education can be reached on 0221 892031, outside those hours the medical on call service on 116 117, and in an acute emergency the number is 112.