Most people come across intermittent fasting because they want to achieve sustainable weight loss results. Nevertheless, the health benefits of intermittent fasting go far beyond that.
Intermittent fasting improves digestion, gut health, life expectancy, and even muscle gain when used correctly.
Unfortunately, most people fail to achieve these successes due to subtle mistakes. With these ten rules for intermittent fasting, that can’t happen to you!
What Are Intermittent Fasting Rules?
Intermittent fasting is an eating pattern that alternates between periods of eating and fasting.
Although there are different methods and rules for intermittent fasting, eating within a window of around 8 hours is the most popular method.
In this sense, this means that 16/8 intermittent fasting involves fasting for 16 hours per day. Nonetheless, you can also fast for 14, 18, or 20 hours daily, as we will cover later.
Because intermittent fasting is associated with health benefits such as increased insulin sensitivity or weight loss, it has recently gained popularity (Halberg et al. 20051).
Since intermittent fasting is a broad and flexible term, various methods and rules. But this is not necessarily a disadvantage.
Intermittent Fasting Rules by Method
Thanks to the flexibility of intermittent fasting, you can tailor your eating habits around your daily routine. Only in this way can you achieve long-term results with intermittent fasting.
Nevertheless, different methods have individual advantages and disadvantages. Therefore, let’s find out which intermittent fasting plan suits your everyday life.
16/8 Intermittent Fasting
The 16/8 method, also known as the peak fasting or lean gains method, allows you to gain muscle while losing body fat.
In this method, you eat between 12 and 8 pm. For this reason, your digestive tract can rest for the remaining 16 hours. After you sleep 8 of the 16 fasting hours, 16/8 intermittent fasting is easier than you might think.
- Fasting window: 16 hours
- Eating window: 8 hours
The Crescendo Method is a softer form of 16/8 Intermittent Fasting.
Instead of fasting every day, you fast on several days throughout the week, for example, Monday, Wednesday, and Friday.
It is especially suitable for starting intermittent fasting. You can try out how your body and its hormonal balance react to the change. If you feel comfortable, you can move on to the 16/8 Intermittent Fasting plan.
- Fasting window: 12-16 hours
- Eating window: 8-12 hours
Alternate Day Fasting (ADF)
This method is just as simple as it sounds – eat one day, fast one day.
However, most people do this by eating a small meal of about 500 calories on a fasting day.
Not only does a small meal make you hungry, but it also negates the health benefits of fasting. Additionally, the insulin release caused by the meal stops fat loss (Meijssen et al. 20012).
For this reason, I would not advise this method.
In addition, ADF is more difficult for many people to integrate into their daily routine than other methods.
- Fasting window: 12-16 hours
- Eating window: 8-12 hours
24-Hour-Fasting or 6:1 Diet
The better version of ADF is 24-hour fasting. Here you do not eat at all on one day of the week and drink only water, coffee, or tea (without additives).
Since you usually fast for two nights, fasting often lasts longer than 24 hours. From dinner to breakfast the day after next, it is usually 36 hours.
You can benefit more from the anti-aging effect of autophagy and burn body fat much more efficiently for energy.
Especially for athletes and people who don’t want to restrict themselves daily, 1-day fasting is a popular option on a rest day.
- Fasting window: 24-40 hours
- Eating window: Rest of the week
48-Hour-Fasting or 5:2 Diet
In the popular version of the 5:2 diet, calorie intake is limited to 500 calories per day for two consecutive days per week (with two meals of 250 calories each).
For the remaining five days of the week, you usually eat. For example, you might eat only 500 calories daily on Monday and Tuesday and typically on Wednesday through Sunday.
The body can no longer break down fat if the insulin level rises due to the meal.
Moreover, fasting periods of 48+ hours are better used selectively as therapeutic fasting methods than to put the body under stress with them every week.
- Fasting window: 48 hours (with small meals)
- Eating window: 5 days of the week
One Meal A Day (OMAD)
OMAD is a more extreme form of the classic 16/8 method.
Therefore, One Meal A Day means nothing more than that you only eat once a day and fast the rest of the day. With this in mind, OMAD is not the proper method for beginners.
Therefore, I see OMAD as a situational method for people who have already practiced 16/8 for a longer time. If it fits into your daily routine, you simply skip another meal.
Accordingly, OMAD is similar to 16/8 and is called the 23/1 fasting or 23/1 diet.
Anyway, with the following fasting pattern, OMAD is even simpler than 16/8 intermittent fasting:
- Fasting window: 23 hours
- Eating window: 1 hour
Do We Need Intermittent Fasting Rules for Weight Loss?
Intermittent fasting sounds very simple. For example, standard 16/8 intermittent fasting has just two rules:
- No breakfast
- No snacks
But even simple concepts hide complex relationships.
You’ve probably read about countless intermittent fasting success stories. You’ve done your research, tried things out, and still aren’t convinced?
Achieving lasting success with intermittent fasting comes down to supposed subtleties.
This article sets up rules for intermittent fasting that get to the heart of all the essential basic principles. If you don’t know this basic information, you will find yourself disappointed over and over again.
In addition, people need clear rules that they can always keep in mind to bring the necessary continuity into their daily lives.
Intermittent Fasting Rules to Get You Results
Here are the top ten rules for intermittent fasting beyond the usual “listen to your body.”
Reflecting the basic principles of years of experience, this concise set of rules has provided both beginners and experts with lasting success in intermittent fasting.
1. What You Eat Matters
Many people abuse intermittent fasting to maintain their habitual Western diet, which is dominated by refined carbohydrates.
However, what you eat makes a big difference, even with intermittent fasting.
People especially like to lie to themselves with alternate day fasting. Perhaps you, too, have acquaintances who practice this method in exchange for stuffing themselves with low-nutrient, high-carbohydrate foods.
Nonetheless, intermittent fasting revolves around two effects:
- Fat burning
- Sustainable health
People tend to forget that research has shown that both goals depend on hormone balance.
For this reason, the desired results fail to materialize when people use intermittent fasting to cheat.
In addition, the constant switch between sugar and fat metabolism also brings physical side effects, such as headaches or diarrhea.
2. Intermittent Fasting Is Not a Diet
Diets have been failing consistently for 50 years. Their lowest common denominator? Calorie counting!
However, the masses have learned little from it to this day.
An empirical study from the United Kingdom shows that 99.5 percent of 99,791 women and 76,704 men failed to lose weight successfully through conventional calorie reduction, even though they were overweight (Fildes et al. 20155).
While calorie balance does impact weight loss, hormonal pathways must first be set to allow fat burning to occur in the first place.
For example, scientists can now predict up to 75% possible gain and loss in overweight people using insulin levels (Kong et al. 20136).
Are you wondering what the most effective way to lower the storage hormone is? It’s fasting.
After a strict fasting period, where you don’t trigger insulin production, insulin levels drop, so you can burn more fat while maintaining your calorie intake throughout the day.
As long as you don’t cheat, intermittent fasting will give you enough daily calories to lose weight. For a woman, that’s about 1,900 kcal per day.
However, this does not mean that you will necessarily eat less. Instead, you fetch your nutrients in fewer, but larger, meals.
According to studies, people who eat fewer meals also consume fewer calories during the day, making them more likely to fall short of their daily requirements (Stubbs et al. 20017).
However, you are still responsible for the quality of the food you eat. If your diet is based on baked goods, pasta, and other refined carbohydrates, hours will pass before the body can burn fat again.
3. Eating Habits Can Be Unlearned
Over the years, we have learned to feel hungry at certain times.
This fact is especially actual for snacks and breakfast. Contrary to popular belief, breakfast is only the most critical meal for the food industry.
In our society, skipping breakfast is almost considered a crime, even if we are not hungry.
But otherwise, we lack energy for the day, don’t we?
Not really. We wake up in the morning at peak levels of adrenaline, glucagon, growth hormone, and cortisol, which provide enough energy to start the day.
Therefore, at no other time in the day are we more energized than after we wake up.
Nevertheless, you can also successfully do Intermittent Fasting by skipping dinner. The great advantage of Intermittent Fasting is that you can build it around your daily routine.
If it fits you and doesn’t cause you to stress, according to my experience, the successes with intermittent fasting are the greatest. Ultimately, the whole package has to fit for a happy personal life.
No matter your daily routine, you will have to unlearn the hunger for snacks to achieve success. Neither anyone needs a snack before noon nor in the afternoon.
Either way, you’ll only become more sluggish and unproductive – wasting valuable time.
Although this may sound challenging, even morning hunger is unlearned in two weeks at the latest. Yet consistency is the key to success.
Regardless of which eating window you choose, you will only eat during this time.
However, after this eating habit can also be learned, your new eating times will become frighteningly regular.
4. Low-Carb and Keto Improve Results
Low-carb and ketogenic diets act as an after-burner on intermittent fasting.
Intermittent fasting and the keto diet pursue the common goal of lowering insulin levels, emptying carbohydrate stores, and entering ketosis.
In this process, your body draws energy preferentially from glycogen stores in the liver, kidneys, and muscles. Once these carbohydrate stores are empty, the body must turn to stored fat for energy.
This fat-burning process is called ketosis and is a natural mechanism that once ensured our survival.
For this reason, the body builds up fat stores during times of abundance to draw on them during a food shortage, such as fasting.
You lose weight as soon as your body burns its fat for energy. When this happens is individual and depends mainly on your diet.
If your carbohydrate stores are full at the beginning of the fast, you won’t lose a gram of fat in the next 24 hours, as they cover your daily requirements.
Depending on your body size, these glycogen stores can hold 1700-2200 calories. For this reason, intermittent fasting works better with a low-carb or keto diet.
If you are already in nutritional ketosis, the body can quickly switch back to burning fat after eating.
Likewise, exercise helps get you into ketosis faster by drawing energy from glycogen stores.
5. Do Not Fear the Shaker
When emptying glycogen stores, the body loses plenty of water. There are about 3 grams of water bound to each gram of carbohydrate.
Therefore, especially when you start intermittent fasting or a ketogenic diet, the body flushes out plenty of electrolytes with water.
As a result, sodium deficiency, in particular, leads to headaches and dizziness.
Although salt has been demonized for decades, we cannot live without sodium. In contrast to the daily requirement of two grams recommended by authorities, our ancestors instinctively consumed 2-3 times as much sodium.
Furthermore, it is the country with the highest salt consumption with the lowest cardiovascular disease rates (Park et al. 20168).
In addition, salt is the natural antagonist of sugar. It takes the bitter taste out of food and counteracts cravings.
Unlike sugar, salt also has a negative feedback loop. The more salt the body gets, the less it craves.
While sugar consumption promotes insulin resistance and body fat storage, salt increases insulin sensitivity and helps weight loss (Sakuyama et al. 20169).
The best options for adding natural salt to your diet are pink Himalayan salt or Celtic sea salt.
So dare to salt as you wish during Intermittent Fasting! Your body will thank you for it.
6. Stay Hydrated
During intermittent fasting, the body loses more water due to the depletion of glycogen stores.
Therefore, it is essential to drink enough to prevent dehydration and headaches. In addition, there are other reasons for increased fluid intake.
For example, people tend to confuse thirst with hunger during intermittent fasting. When we give up habitual snacks, the body also lacks the fluids they had given us.
Accordingly, you often don’t have a craving for food but rather a hidden desire for fluids. However, how much you should drink per day cannot be generalized.
Neither do utopian recommendations of 5 liters of water per day apply to everyone, nor can water requirements be calculated based on body weight, size, or age.
Therefore, a simple rule of thumb applies: Drink when thirsty. In addition, it makes sense to drink a cup of tea or a glass of water when the hunter arises. If the hunger subsides after half an hour, you are just thirsty.
However, if you’re not thirsty, you don’t have to constantly force yourself to drink.
When in doubt, a glass of water or tea won’t hurt. With more extended periods of fasting and experience, you will get a better sense of when you are thirsty.
Since carbohydrates bind water in the body, a low-carb approach also makes sense from this perspective.
If you eat, e.g., bread, cookies, or cereal bars between fasting periods, water is stored, flushed out again along with sodium, and causes headaches.
With this in mind, my tip is to drink mineral water during intermittent fasting. Highly mineralized natural water can give you the electrolytes you lose during fasting.
You will find information about sodium, potassium, magnesium, calcium, and chloride on the label of good mineral water.
7. Do Not Put Milk in Your Coffee
When drinking water, coffee, or tea, mistakes repeatedly happen during intermittent fasting, which clear rules can prevent. In the end, many beginners usually just lack reliable information.
Thus, many fasting beginners get carried away and add a splash of milk or sugar to their black coffee.
But these subtle little things can have significant effects. By raising blood sugar and insulin levels, they break the fast. So, time and time again, a good portion of the health benefits and progress in losing weight are negated.
For example, ketogenic diet followers also tend to forget that Bulletproof Coffee breaks the fast.
So while butter, coconut, or MCT oil in coffee helps with hunger between meals, it prevents the full health benefits of fasting.
Finally, you also need to burn the fat from Bulletproof Coffee before the body into its fat stores.
Although bone broth is also a prime source of electrolytes and fat, it, too, technically breaks the fast and should only be used as a jump start. Once you get used to intermittent fasting, it’s just as taboo as Bulletproof Coffee.
Furthermore, many people don’t realize that while light and zero drinks are sugar-free, they can still break the fast.
8. Stay Away From Sweeteners
Sugar-free light drinks are popular not only for diets but in general. Nevertheless, it is these drinks that prevent success in intermittent fasting.
Contrary to the advertising message, zero sugar does not stand for fat burning in reality.
Moreover, they erase gut bacteria that guarantee our health (Ruiz-Ojeda und Plaza-Díaz 201911).
Because sugar-free drinks hardly increase blood sugar levels, they trigger cravings for sweets in the brain. Therefore, sweeteners make people hungrier than conventional sugar (Yang 201012).
People who consume diet products like water are more often overweight, a proven fact.
Accordingly, researchers at the University of Texas at San Antonio found that consuming light beverages increases the likelihood of weight gain by 47 percent (Fowler et al. 200813).
During the fasting period, fluid intake is essential. However, it should be limited to water, mineral water, tea, and coffee without additives.
On the one hand, diet sodas break the fast. On the other hand, they will push your goals further away, even during eating periods.
9. Fasting Must Not Be Stressful
Stress is a significant factor that tends to be overlooked in intermittent fasting. When stress levels are too high, it often happens that weight stagnates.
After being exposed to psychological stressors regularly, the body releases cortisol more often than is healthy for us.
Cortisol is the crucial steroid hormone for the body’s effective stress response.
For this reason, cortisol has been evolutionarily essential to prepare the body for fight or flight. For example, to escape the threat of an onrushing wild animal.
After cortisol is released, blood sugar rises. In short, the body mobilizes energy to escape danger as quickly as possible (Owen et. al 197314).
Since elevated blood glucose increases insulin secretion, cortisol can indirectly inhibit fat burning.
For this reason, prolonged stress promotes weight gain, insulin resistance, and diabetes in the long run (Rizza et al. 198215).
After it is one of the crucial rules that your stress does not increase, your intermittent fasting plan must also fit into your daily routine.
The primary advantage of intermittent fasting is the degree of flexibility. If you have a busy calendar and no time to prepare an authentic meal, you can always skip it.
While my preference is to skip breakfast, it may mean less stress for you to skip dinner. Some of my readers get the most results by eating only at lunchtime.
Ultimately, fasting is about less, not more. No longer dividing your day by fixed meals can be liberating and mean less stress.
10. You Don’t Have to Take It Easy
A popular myth about intermittent fasting is that you must take it easy.
If you’re already tired, the surest way into sluggishness is to rest even more. Instead, activities can help your body go fat-burning faster.
If you feel fatigued while fasting, it’s usually a sign that your carbohydrate stores are emptying. However, this is not a bad thing.
The body is telling us that readily available energy is running low by feeling sluggish. And that’s precisely what we want to achieve.
Nevertheless, the body does not immediately expend extra metabolic energy to burn fat, especially if you have just started fasting.
Accordingly, body fat is like a savings account. You only withdraw from it when the checking account (carbohydrate store) is empty.
That’s why it helps to increase your energy needs with exercise. This way, you force your body to switch to burning body fat for energy.
Nonetheless, when fasting, it is crucial to listen to your body. If you feel good about fasting and strength training, there is nothing wrong with it.
If you feel unwell, you can always break the fast.
For example, gaining muscle on intermittent fasting works excellently since it amplifies growth hormone secretion.
The golden rule is to always exercise during the fasting period to maximize fat burning.
If you eat before exercising, the increased insulin spike will hinder fat burning (Meijssen et al. 200116).
Intermittent Fasting Rules Path the Way to Success
The timing of eating is the most critical factor in losing weight, and it has been overlooked for decades.
Anyone who still believes that eating many small meals a day helps with weight loss is far from the reality of science.
Accordingly, studies confirm that people who eat snacks eat more daily (Stubbs et al. 200117).
In addition, it is a fact that snacks do not help with weight loss (Cameron et al. 201018).
You need clear rules to reap the myriad health benefits of intermittent fasting. Ultimately, fasting means not just going without sporadically.
The simple approach quickly becomes complex.
If you use these rules as a guide, you can find your path to intermittent fasting and achieve visible success.
Intermittent Fasting Rules FAQ
What is allowed during intermittent fasting?
During the fasting period, eating is prohibited. However, coffee ☕ and tea 🍵 without milk and sugar are allowed.
What can you eat or drink while intermittent fasting?
There is no eating during the fasting period, but you may drink water, coffee ☕, and tea 🍵 without milk and sugar.
What can you not eat during intermittent fasting?
There is no eating during the fasting period. However, you may eat during the eating window (e.g., 8 hours a day). For best results, stick to a low-carb or keto diet.
What liquids can you drink while intermittent fasting?
You may drink water, mineral water, coffee ☕, and tea 🍵 without milk, sugar, or sweeteners while intermittent fasting.
1Halberg N, Henriksen M, Söderhamn N, Stallknecht B, Ploug T, Schjerling P, Dela F. Effect of intermittent fasting and refeeding on insulin action in healthy men. J Appl Physiol (1985). 2005 Dec;99(6):2128-36. doi: 10.1152/japplphysiol.00683.2005. Epub 2005 Jul 28. PubMed PMID: 16051710.
2Meijssen S, Cabezas MC, Ballieux CG, Derksen RJ, Bilecen S, Erkelens DW. Insulin mediated inhibition of hormone sensitive lipase activity in vivo in relation to endogenous catecholamines in healthy subjects. J Clin Endocrinol Metab. 2001 Sep;86(9):4193-7. doi: 10.1210/jcem.86.9.7794. PubMed PMID: 11549649.
3Levine B, Klionsky DJ. Autophagy wins the 2016 Nobel Prize in Physiology or Medicine: Breakthroughs in baker’s yeast fuel advances in biomedical research. Proc Natl Acad Sci U S A. 2017 Jan 10;114(2):201-205. doi: 10.1073/pnas.1619876114. Epub 2016 Dec 30. PubMed PMID: 28039434; PubMed Central PMCID: PMC5240711.
4Meijssen S, Cabezas MC, Ballieux CG, Derksen RJ, Bilecen S, Erkelens DW. Insulin mediated inhibition of hormone sensitive lipase activity in vivo in relation to endogenous catecholamines in healthy subjects. J Clin Endocrinol Metab. 2001 Sep;86(9):4193-7. doi: 10.1210/jcem.86.9.7794. PubMed PMID: 11549649.
5Fildes A, Charlton J, Rudisill C, Littlejohns P, Prevost AT, Gulliford MC. Probability of an Obese Person Attaining Normal Body Weight: Cohort Study Using Electronic Health Records. Am J Public Health. 2015 Sep;105(9):e54-9. doi: 10.2105/AJPH.2015.302773. Epub 2015 Jul 16. PubMed PMID: 26180980; PubMed Central PMCID: PMC4539812.
6Kong LC, Wuillemin PH, Bastard JP, Sokolovska N, Gougis S, Fellahi S, Darakhshan F, Bonnefont-Rousselot D, Bittar R, Doré J, Zucker JD, Clément K, Rizkalla S. Insulin resistance and inflammation predict kinetic body weight changes in response to dietary weight loss and maintenance in overweight and obese subjects by using a Bayesian network approach. Am J Clin Nutr. 2013 Dec;98(6):1385-94. doi: 10.3945/ajcn.113.058099. Epub 2013 Oct 30. PubMed PMID: 24172304.
7Stubbs RJ, Mazlan N, Whybrow S. Carbohydrates, appetite and feeding behavior in humans. J Nutr. 2001 Oct;131(10):2775S-2781S. doi: 10.1093/jn/131.10.2775S. Review. PubMed PMID: 11584105.
8Park J, Kwock CK, Yang YJ. The Effect of the Sodium to Potassium Ratio on Hypertension Prevalence: A Propensity Score Matching Approach. Nutrients. 2016 Aug 6;8(8). doi: 10.3390/nu8080482. PubMed PMID: 27509520; PubMed Central PMCID: PMC4997395.
9Sakuyama H, Katoh M, Wakabayashi H, Zulli A, Kruzliak P, Uehara Y. Influence of gestational salt restriction in fetal growth and in development of diseases in adulthood. J Biomed Sci. 2016 Jan 20;23:12. doi: 10.1186/s12929-016-0233-8. Review. PubMed PMID: 26787358; PubMed Central PMCID: PMC4719732.
10Anton SD, Martin CK, Han H, Coulon S, Cefalu WT, Geiselman P, Williamson DA. Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels. Appetite. 2010 Aug;55(1):37-43. doi: 10.1016/j.appet.2010.03.009. Epub 2010 Mar 18. PubMed PMID: 20303371; PubMed Central PMCID: PMC2900484.
11Ruiz-Ojeda FJ, Plaza-Díaz J, Sáez-Lara MJ, Gil A. Effects of Sweeteners on the Gut Microbiota: A Review of Experimental Studies and Clinical Trials. Adv Nutr. 2019 Jan 1;10(suppl_1):S31-S48. doi: 10.1093/advances/nmy037. PubMed PMID: 30721958; PubMed Central PMCID: PMC6363527.
12Yang Q. Gain weight by “going diet?” Artificial sweeteners and the neurobiology of sugar cravings: Neuroscience 2010. Yale J Biol Med. 2010 Jun;83(2):101-8. Review. PubMed PMID: 20589192; PubMed Central PMCID: PMC2892765
13Fowler SP, Williams K, Resendez RG, Hunt KJ, Hazuda HP, Stern MP. Fueling the obesity epidemic? Artificially sweetened beverage use and long-term weight gain. Obesity (Silver Spring). 2008 Aug;16(8):1894-900. doi: 10.1038/oby.2008.284. Epub 2008 Jun 5. PubMed PMID: 18535548.
14Owen OE, Cahill GF Jr. Metabolic effects of exogenous glucocorticoids in fasted man. J Clin Invest. 1973 Oct;52(10):2596-605. doi: 10.1172/JCI107452. PubMed PMID: 4729053; PubMed Central PMCID: PMC302520.
15Rizza RA, Mandarino LJ, Gerich JE. Cortisol-induced insulin resistance in man: impaired suppression of glucose production and stimulation of glucose utilization due to a postreceptor detect of insulin action. J Clin Endocrinol Metab. 1982 Jan;54(1):131-8. doi: 10.1210/jcem-54-1-131. PubMed PMID: 7033265.
16Meijssen S, Cabezas MC, Ballieux CG, Derksen RJ, Bilecen S, Erkelens DW. Insulin mediated inhibition of hormone sensitive lipase activity in vivo in relation to endogenous catecholamines in healthy subjects. J Clin Endocrinol Metab. 2001 Sep;86(9):4193-7. doi: 10.1210/jcem.86.9.7794. PubMed PMID: 11549649.
17Stubbs RJ, Mazlan N, Whybrow S. Carbohydrates, appetite and feeding behavior in humans. J Nutr. 2001 Oct;131(10):2775S-2781S. doi: 10.1093/jn/131.10.2775S. Review. PubMed PMID: 11584105.
18Cameron JD, Cyr MJ, Doucet E. Increased meal frequency does not promote greater weight loss in subjects who were prescribed an 8-week equi-energetic energy-restricted diet. Br J Nutr. 2010 Apr;103(8):1098-101. doi: 10.1017/S0007114509992984. Epub 2009 Nov 30. PubMed PMID: 19943985.