Cravings During Intermittent Fasting: Causes and What May Help
Cravings are not proof that you are too weak. They are a message from your body. Here you can read which causes may be behind them and where you can start.
When cravings overwhelm someone during fasting, the usual advice is: more discipline. I believe the better question is: What is your body trying to tell you right now?
It's 3 pm. Your eating window doesn't open until 6 pm. And suddenly you can think of nothing but chocolate.
Or it's 9 pm, and the window closed long ago. You're standing in front of the fridge and not quite sure how you got there.
If this sounds familiar, you are not alone. And you are not broken. Cravings are rarely a character flaw. More often they are a signal pointing to something: your blood sugar, your meals, your sleep or your stress level.
Why is hunger during fasting not the same as a craving?
Do you know the difference between a quiet rumble in your stomach and a feeling that almost pulls you toward food? Both are called hunger. But they are two different things.
Normal hunger arrives slowly. It's like an ebb tide announcing itself. You could wait another hour, and it would be fine. A craving, by contrast, is like a wave that suddenly breaks. It wants something specific, usually sweet or fatty, and it wants it now.
Your body has its own messenger for hunger: ghrelin. It is produced mainly in the stomach. Imagine it as an alarm clock your body sets to your usual mealtimes.
A team led by Cummings at the University of Washington took blood samples 38 times over 24 hours from healthy people. Ghrelin levels rose to almost double before each meal and fell again within an hour after eating. What this means for you: your hunger follows a learned rhythm and can also relearn.
Cummings DE et al. Diabetes. 2001. DOI: 10.2337/diabetes.50.8.1714This explains why the first days of intermittent fasting are often the hardest. The alarm clock still rings at your old breakfast time. It doesn't know that you've changed your routine.
A team led by Elsworth at the University of Bristol analysed 17 randomised trials on intermittent fasting and appetite. Hunger, fullness and desire to eat did not clearly differ from classic calorie restriction. So intermittent fasting is neither a hunger booster nor a magic remedy against hunger.
Elsworth RL et al. Nutrients. 2023. DOI: 10.3390/nu15112604The research group led by Varady at the University of Illinois Chicago followed people with obesity for eight weeks of alternate day fasting. Although ghrelin rose, hunger did not increase by the end, and fullness even went up. So your body can adapt, even if the start is bumpy.
Hoddy KK et al. Clin Nutr. 2016. DOI: 10.1016/j.clnu.2016.03.011Hunger during fasting is to be expected. Cravings that don't quiet down over weeks are something else. They are not a test of your willpower but an invitation to take a closer look.
And now you know why hunger is allowed to be loud at the beginning, and why persistent cravings raise a different question.
The blood sugar rollercoaster: when the crash after eating wakes up hunger
Maybe you've experienced this: you break your fast with a big plate of pasta or a croissant. An hour later you feel great. Two hours later you're tired, irritable and hungrier than before.
Imagine your blood sugar as a rollercoaster. A very quickly digested meal pushes the car steeply upward. Your body releases a lot of insulin to bring the sugar into the cells. Sometimes it overshoots. The car then plunges below its starting point. And your brain appears to read exactly this dip as an alarm.
Researchers led by Wyatt and Valdes at King's College London used glucose sensors to measure blood sugar after standardised meals in more than a thousand people. It was not the peak after eating that best predicted later hunger, but the drop two to three hours afterwards. People with larger dips became hungrier, ate again sooner and took in more energy over 24 hours.
Wyatt P et al. Nat Metab. 2021. DOI: 10.1038/s42255-021-00383-xThe associations in this study were statistically clear but not huge. So blood sugar is not the only lever for hunger. It is, however, one you can help shape through your meals.
Seen through the KPNI lens, this touches several systems at once. The dip arises in your metabolism. The nervous system reacts with restlessness because the brain depends on a stable sugar supply. The hormonal system sends out counterparts such as adrenaline and cortisol to raise blood sugar again. No wonder a dip sometimes feels like stress.
Fast meal
Lots of easily digested starch or sugar, little protein, little fibre.
Steep rise
Blood sugar rises quickly, and the pancreas releases a lot of insulin.
Dip after two to three hours
In some people, blood sugar then falls below its starting value.
Hunger signal
The brain may respond with restlessness and cravings, often right when your fasting window begins.
The craving at 4 pm may have its roots in the meal at 1 pm. Instead of pushing it away, it's worth asking: How was my last meal built?
And now you know why the meal before your fasting break can be at least as important as the break itself.
Too little protein: the silent hunger maker
When the eating window gets shorter, many people unknowingly eat less protein. A quick sandwich, a bowl of muesli, something warm in the evening. It feels filling. For a few hours.
For your satiety, protein is something like a long log in the stove. Sugar burns fast and bright. Protein keeps glowing for a long time. It stimulates satiety hormones in the gut and takes time to digest.
A team led by Weigle at the University of Washington raised dietary protein from 15 to 30 percent while keeping carbohydrates the same. Satiety rose noticeably, and when participants were allowed to eat freely, they ate on average around 440 kilocalories less per day. More protein may therefore feel to you like a natural hunger dampener.
Weigle DS et al. Am J Clin Nutr. 2005. DOI: 10.1093/ajcn.82.1.41A group led by Leidy at the University of Missouri gave young women who usually skipped breakfast either a normal or a high protein breakfast. Both breakfasts reduced sweet and savoury cravings compared with skipping, and the high protein version tended to dampen savoury cravings more strongly. At the same time, a blood marker for dopamine, the messenger for reward, increased.
Hoertel HA et al. Nutr J. 2014. DOI: 10.1186/1475-2891-13-80This study was small, and it was about breakfast, not fasting. The direction is still interesting: a protein rich meal might engage the reward system in a way that lessens the urge for a quick hit. In my clinical experience, many people notice their cravings easing when the first meal of the eating window is truly filling. That is experience, not proof from studies.
Good protein sources can include eggs, yoghurt, quark, legumes, tofu, tempeh or meat. You can read more about protecting your muscles while fasting in the article Fasting and muscle loss.
You don't have to eat less to have fewer cravings. Sometimes it may help more to eat more of the right things during your eating window. That can feel paradoxical, but it is physiologically plausible.
And now you know why your plate sometimes matters more than your clock.
Stress hormones and sleep: when your nervous system eats with you
Have you noticed that cravings are worse on stressful days? Or after a night when you slept only five hours? That's no coincidence.
Cortisol is your alarm hormone. In the short term it's useful: it raises blood sugar and makes you alert. But when the alarm runs constantly, it may tune the brain's reward system toward quick energy. Your body believes it has to prepare for danger. And danger calls for calories.
A team led by Epel at Yale University observed healthy women on a stress day and on a calm day. Women with a strong cortisol response ate more calories on the stress day than women with a weak response, and overall they reached for sweets more often. So your craving for chocolate after a hard day may be a physical stress response.
Epel E et al. Psychoneuroendocrinology. 2001. DOI: 10.1016/s0306-4530(00)00035-4Adam and Epel at the University of California San Francisco brought together animal and human data on stress and eating. They describe a model in which cortisol and the reward system together may increase the desire for calorie dense foods. Interesting for you: repeated, unsuccessful diet attempts are also discussed there as a possible amplifier.
Adam TC, Epel ES. Physiol Behav. 2007. DOI: 10.1016/j.physbeh.2007.04.011Fasting itself is also a small stress stimulus. In the right dose, it can train you. But stress adds up. A full working day, a short night and a long fasting window together may be more than your system can carry right now.
A team led by Spiegel and Van Cauter at the University of Chicago had young men sleep briefly for two nights and long for two nights. After short sleep, the satiety hormone leptin fell by 18 percent, ghrelin rose by 28 percent, and hunger increased by 24 percent. Appetite for calorie dense, carbohydrate rich foods rose in particular.
Spiegel K et al. Ann Intern Med. 2004. DOI: 10.7326/0003-4819-141-11-200412070-00008Cravings after a bad night are not a failure. It is your body trying to make up for missing recovery with energy. Once you understand that, you stop fighting yourself. And that is a kind of freedom.
If you notice that your nervous system is constantly running at full throttle, the article Breathing techniques and the vagus nerve offers approaches that may help you calm it.
On days after short nights or high stress, your fasting window is allowed to be wider. That's not an excuse but smart dosing. Fasting is meant to strengthen you, not add to your load.
And now you know why sleep and stress also have a seat at the table when you fast.
Magnesium and micronutrients: what is supported by evidence and what isn't
Maybe you've read that a craving for chocolate is a sign of magnesium deficiency. It sounds plausible, since cocoa contains magnesium. But honesty is worth it here.
Magnesium is something like a lubricant for hundreds of enzymes. Among other things, your body needs it so that insulin can dock properly at the cell. If it is lacking, blood sugar regulation might become a bit bumpier. And bumpy blood sugar can, as you saw above, fuel hunger.
A team led by Veronese at the University of Padua analysed 18 double blind trials on magnesium in people with diabetes or at increased risk of diabetes. In diabetes, fasting blood sugar decreased, and in people at risk, the glucose value in the tolerance test improved. This does not show a direct effect on cravings, but a possible pathway through more stable blood sugar.
Veronese N et al. Eur J Clin Nutr. 2016. DOI: 10.1038/ejcn.2016.154Researchers led by Boyle at the University of Leeds reviewed studies on magnesium and subjective anxiety. About half of the studies in vulnerable groups showed a favourable effect, but study quality was weak. So magnesium might also play a role via the stress axis, but this has not been established yet.
Boyle NB et al. Nutrients. 2017. DOI: 10.3390/nu9050429That is why, in functional medicine, we look not only at willpower when cravings are persistent, but also at micronutrient status. Besides magnesium, iron and vitamin B12, for example, can influence energy and drive. Only a laboratory test can show whether a deficiency is present. Supplementing blindly does not replace it. If you're interested in which form of magnesium may suit you, read Which magnesium is best?
Not every chocolate craving is a cry for magnesium. But when cravings come together with fatigue, muscle cramps or inner restlessness, a look at your lab values may make more sense than yet another resolution.
And now you know where the science stands on micronutrients and where speculation begins.
When you eat during the day may shape your hunger
Many people fast in the morning and eat in the evening. It fits their daily life. But your body has an internal clock, and it doesn't tick evenly.
Researchers led by Ravussin and Peterson at the Pennington Biomedical Research Center had people with overweight eat either from 8 am to 2 pm or from 8 am to 8 pm, with the same amount of calories. The early eating window lowered the average ghrelin level and made hunger more even across the day. So when you eat might help determine how strongly hunger grips you later.
Ravussin E et al. Obesity. 2019. DOI: 10.1002/oby.22518A team led by Sutton and Peterson had men with prediabetes eat within an early six hour window for five weeks, with dinner before 3 pm. Alongside insulin sensitivity and blood pressure, appetite also improved, without the men losing weight. The group was small, but the direction matches the study above.
Sutton EF et al. Cell Metab. 2018. DOI: 10.1016/j.cmet.2018.04.010Such an early window doesn't fit every life, and it doesn't have to. Even a slightly earlier dinner may be worth an experiment. You can find more on the basics in the article Understanding 16:8 intermittent fasting.
The best eating window is not the one with the longest fast. It is the one in which your hunger stays calmest and that you can live with in the long run.
And now you know why the time of day can also be a lever.
Reading cravings as a signal: your personal search for causes
Instead of asking yourself "Why am I so weak?", you could ask: "What am I missing right now?" This question can change a lot. It turns self criticism into curiosity.
Two to three hours after eating
A possible hint of a blood sugar dip. Check how much protein, fibre and fat your meal contained.
After short nights
A possible hint that lack of sleep is a driver. Leptin falls, ghrelin rises.
On stressful days
A possible hint of the stress axis. Sweets become quick comfort.
With fatigue and cramps
A possible hint of a micronutrient deficiency. A lab check may bring clarity here.
Questions for your hunger diary
- When exactly do the cravings appear, and what did I eat before?
- How much protein was in my last meal?
- How did I sleep the night before?
- How high was my stress level that day, on a scale from one to ten?
- What exactly am I craving: something sweet, salty, fatty or simply anything?
Just two weeks of such notes can reveal patterns you hadn't noticed before. Conventional medical assessment, for example if diabetes or a thyroid disorder is suspected, remains important. What an integrative view can add is a look at the interplay of meals, sleep, stress and micronutrients.
An important note: if cravings turn into binge eating, or if food hardly leaves your mind, fasting may not be the right tool for you right now. In that case, a break and medical or psychotherapeutic support make more sense than more strictness.
Cravings are not a defeat in a battle against yourself. They are a message. The better you learn to read it, the less you have to fight it.
And now you know why curiosity may carry you further than discipline when you fast.
Your three levers for this week
- Rebuild the last meal before your break: Start it with protein and vegetables, and move fast carbohydrates toward the end.
- Make sleep a fasting rule: After a night of less than six hours, your eating window is allowed to be wider that day.
- Two weeks of a hunger diary: When cravings come, note the time, your last meal, your sleep and your stress.
More from the Fasting Guide
Further articles in the Fasting Guide
- Understanding 16:8 intermittent fasting
- Fasting for beginners
- Fasting and blood sugar
- Fasting and muscle preservation
- Fasting for women and the cycle
- Fasting during menopause
- Fasting with Hashimoto's
- What breaks a fast?
- Breaking your fast the right way
- Autophagy: when does it begin?
- The fasting mimicking diet (FMD) explained
- Water fasting and its risks
Where this topic connects
Cravings touch metabolism, the nervous system, the hormonal system and nutrition all at once. These articles go deeper into the neighbouring layers.
Blood sugar and insulin
What insulin resistance means and how your eating rhythm may influence it.
MetabolismThe first meal
How you can break your fast so that blood sugar may stay calmer.
NutritionMagnesium compared
Which forms of magnesium exist and how they differ.
MicronutrientsBreathing techniques and the vagus nerve
How you may calm your nervous system during stressful phases.
Nervous systemFrequently asked questions about cravings during intermittent fasting
Are cravings during intermittent fasting normal?
Cravings in the first few weeks are common and not a sign of weakness. Your hunger hormone ghrelin follows familiar mealtimes and needs time to adjust to a new rhythm. If strong cravings persist for weeks, though, it may be worth looking at possible causes such as blood sugar swings, too little protein, stress or lack of sleep. At that point they are more likely a signal than a discipline problem.
Why do I crave sweets when I fast?
Sweet cravings can have several reasons. A large study in Nature Metabolism found that a sharp drop in blood sugar two to three hours after a meal was associated with more hunger and higher calorie intake. Stress can also increase the desire for sweets: in a laboratory study, women with a strong cortisol response ate more sweet foods. That is why the last meal before your fasting break may play an important role.
How long does it take for hunger to settle during intermittent fasting?
Many people report that their hunger calms down after a few weeks. In a study of alternate day fasting over eight weeks, hunger did not increase despite weight loss, and fullness even rose. How quickly this happens for you depends, among other things, on sleep, stress and the composition of your meals. Regular mealtimes may make the adjustment easier.
Does protein help against cravings while fasting?
Protein can noticeably support satiety. In a University of Washington study, satiety increased when dietary protein was raised from 15 to 30 percent, and participants spontaneously ate around 440 kilocalories less per day. A small pilot study found that a high protein breakfast tended to dampen savoury cravings more strongly. A protein rich first and last meal may therefore be a useful lever.
Can magnesium deficiency trigger cravings?
Direct proof that magnesium deficiency causes cravings is still lacking. Magnesium is, however, involved in glucose metabolism: a meta-analysis of randomised trials showed that magnesium can improve blood sugar levels and insulin sensitivity in people with diabetes or at increased risk. A systematic review found hints that magnesium might have a favourable effect on subjective anxiety in vulnerable people, although study quality was weak. A laboratory test can show whether a deficiency is present.
Why am I hungrier while fasting after a bad night's sleep?
Lack of sleep changes your hunger hormones. In a study at the University of Chicago, two nights of restricted sleep lowered the satiety hormone leptin by 18 percent and raised the hunger hormone ghrelin by 28 percent. Hunger increased by 24 percent, especially for carbohydrate rich, calorie dense foods. On days after short nights, a gentler fasting break may make sense.
Does intermittent fasting cause more hunger than a regular diet?
According to a meta-analysis of 17 randomised trials with more than 1,100 participants, hunger during intermittent fasting does not clearly differ from classic calorie restriction. So intermittent fasting is neither a hunger booster nor a hunger stopper. How you feel depends strongly on how you build your meals and what your daily life looks like.
What can I do when cravings hit me in the evening?
Evening cravings often have to do with how your day went: too little protein during the day, a blood sugar low in the afternoon or a high stress level. A study on early time restricted eating showed that an earlier eating window made hunger more even and lowered the hunger hormone ghrelin. An earlier eating window, a filling main meal and a calm evening may therefore be starting points.
When should I pause intermittent fasting because of cravings?
If cravings turn into binge eating, you are constantly preoccupied with food or you feel guilty after eating, a break makes sense. This applies especially if you have a history of an eating disorder. With diabetes treated with glucose lowering medication, and during pregnancy and breastfeeding, fasting should only happen after consulting a doctor.
Sources
- Cummings DE, Purnell JQ, Frayo RS et al. A preprandial rise in plasma ghrelin levels suggests a role in meal initiation in humans. Diabetes. 2001;50(8):1714-1719. DOI: 10.2337/diabetes.50.8.1714 [Pathophysiology, human study, n=10]
- Elsworth RL, Monge A, Perry R et al. The effect of intermittent fasting on appetite: a systematic review and meta-analysis. Nutrients. 2023;15(11):2604. DOI: 10.3390/nu15112604 [Meta-analysis, 17 RCTs, n=1,111]
- Hoddy KK, Gibbons C, Kroeger CM et al. Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clin Nutr. 2016;35(6):1380-1385. DOI: 10.1016/j.clnu.2016.03.011 [Pathophysiology, intervention study without control group, n=59]
- Wyatt P, Berry SE, Finlayson G et al. Postprandial glycaemic dips predict appetite and energy intake in healthy individuals. Nat Metab. 2021;3(4):523-529. DOI: 10.1038/s42255-021-00383-x [Real world cohort, n=1,070]
- Weigle DS, Breen PA, Matthys CC et al. A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. Am J Clin Nutr. 2005;82(1):41-48. DOI: 10.1093/ajcn.82.1.41 [Pathophysiology, intervention study, n=19]
- Hoertel HA, Will MJ, Leidy HJ. A randomized crossover, pilot study examining the effects of a normal protein vs. high protein breakfast on food cravings and reward signals in overweight/obese "breakfast skipping", late-adolescent girls. Nutr J. 2014;13:80. DOI: 10.1186/1475-2891-13-80 [RCT, crossover, pilot study, n=20]
- Epel E, Lapidus R, McEwen B, Brownell K. Stress may add bite to appetite in women: a laboratory study of stress-induced cortisol and eating behavior. Psychoneuroendocrinology. 2001;26(1):37-49. DOI: 10.1016/s0306-4530(00)00035-4 [Pathophysiology, laboratory study, n=59]
- Adam TC, Epel ES. Stress, eating and the reward system. Physiol Behav. 2007;91(4):449-458. DOI: 10.1016/j.physbeh.2007.04.011 [Review, human and animal]
- Spiegel K, Tasali E, Penev P, Van Cauter E. Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite. Ann Intern Med. 2004;141(11):846-850. DOI: 10.7326/0003-4819-141-11-200412070-00008 [RCT, crossover, n=12]
- Veronese N, Watutantrige-Fernando S, Luchini C et al. Effect of magnesium supplementation on glucose metabolism in people with or at risk of diabetes: a systematic review and meta-analysis of double-blind randomized controlled trials. Eur J Clin Nutr. 2016;70(12):1354-1359. DOI: 10.1038/ejcn.2016.154 [Meta-analysis, 18 RCTs]
- Boyle NB, Lawton C, Dye L. The effects of magnesium supplementation on subjective anxiety and stress: a systematic review. Nutrients. 2017;9(5):429. DOI: 10.3390/nu9050429 [Systematic review, 18 studies]
- Ravussin E, Beyl RA, Poggiogalle E et al. Early time-restricted feeding reduces appetite and increases fat oxidation but does not affect energy expenditure in humans. Obesity. 2019;27(8):1244-1254. DOI: 10.1002/oby.22518 [RCT, crossover, n=11]
- 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 [RCT, crossover, controlled feeding study]
All sources were checked via PubMed for title, authors, year, DOI and abstract. Figures are taken from the abstracts. Studies that examine cravings directly during intermittent fasting are still rare. Many statements are therefore based on studies of appetite regulation, blood sugar, protein, stress and sleep that are applied to fasting. A direct link between magnesium deficiency and cravings has not yet been demonstrated by studies.