Intermittent Fasting 16/8: The Complete Hands-on Guide

fact-checked article

16/8 | Intermittent Fasting | Pros | Cons | Tips | Schedule | Recipes

Almost every culture and religion ingrains fasting. Its scientifically proven health benefits best show why it has been effectively practiced for thousands of years.

For this reason, intermittent fasting has gained immense popularity, with 16/8 being the most widespread method.

In addition, 16/8 intermittent fasting is mainly considered sustainable and safe.

What Is Intermittent Fasting 16/8?

In 16 to 8 intermittent fasting, you eat within a specific time window and fast during the day’s rest.

For this reason, this intermittent fasting protocol is also known as time-restricted eating (TRE) or peak fasting. Since you can also use the method excellently for building muscle mass while losing body fat, it is also called the lean gains method.

Although many forms of intermittent fasting exist, 16/8 is the most common method. 

In addition to 16/8 intermittent fasting, the following intermittent fasting schedules are popular:

  • 1-Day Fasting or 6:1 diet – you don’t eat at all one day a week.
  • Alternate Day Fasting (ADF) – eat and fast one day.
  • One Meal A Day (OMAD) – 23/1 Intermittent Fasting where you eat once daily.

Because of the simple framework, 16/8 has proven to be the best intermittent fasting method for beginners, particularly in my experience.


The classic 16/8 intermittent fasting protocol has just two rules:

  • No breakfast
  • No snacks

That’s it. Health can be that simple.

There is no eating during the fasting period. If you feel hungry or thirsty, you may consume the following beverages at any time:

However, you must avoid additives such as milk, sugar, or sweeteners in these drinks to avoid breaking the fast.

Fasting Times

For example, in the 16/8 method, you eat lunch at noon and dinner at 8 p.m. During this 8-hour eating window, snacks are generally allowed.

This way, your body can fast for the remaining 16 of the 24 hours per day.

Since you sleep 8 hours during fasting,  there are only 8 hours of fasting while awake.

The fasting period from 8:00 p.m. to the next day’s noon ensures that your entire digestive tract rests for 16 hours at a stretch.

Therefore, to start 16/8 Intermittent Fasting, all you have to do is skip breakfast.

After mainly highly processed products are put on the table, breakfast is the most important meal of the day, but only for the food industry.

Because the body increases adrenaline, glucagon, growth hormone, and cortisol levels, we wake up in the morning. For this reason, energy levels are even more stable when fasting until noon than in the case of breakfast.

You will recognize this in increased productivity once you get used to 16/8 and unlearn the hunger in the morning.

However, if you have exceptional work schedules, you can just as quickly eliminate evening or lunch and have success.

If you maintain a fasting period of 16 hours, you can flexibly integrate 16/8 intermittent fasting into any daily routine.

Weight Loss

People successfully lose weight with intermittent fasting for a good reason: fasting is the best way to lower insulin levels. 

Insulin is responsible for signaling cells to take up glucose from the bloodstream and store excess energy as fat. 

Accordingly, using insulin levels, researchers can predict 75% of the gain and loss in overweight people (Kong et al. 20131).

Moreover, high insulin levels prevent the breakdown of body fat (Meijssen et al. 20012).

The 16-hour fasting stops nutrient intake and lowers insulin levels, ending the body’s storage mode. 

For this reason, the body can deplete carbohydrate stores (glycogen). Once these are empty, they can tap into body fat for energy. 

This natural process is called ketosis. After most people want to lose weight, ketosis is the essential goal of intermittent fasting 16/8. 

Consequently, our bodies build up fat reserves during times of abundance to burn for energy during food shortages. 

Because we now eat all seasons around the clock, we gain weight. In contrast, intermittent fasting can restore the natural balance between eating and fasting. 

Accordingly, fasting corrects the hormonal imbalance that causes obesity (Lustig 20013). 


As we have just learned, a strict fasting period forces the body to break down stored carbohydrates and burn body fat for energy.

This completely natural state of particularly effective fat-burning is called ketosis. Moreover, ketosis is the eponym of the ketogenic diet.

This way of eating is a special low-carb, high-fat (LCHF) diet. Hence, you consume about 75-80% of your calories from fats, 20-25% from proteins, and about 5-10% from carbohydrates on keto.

Furthermore, it does nothing but mimics the state of fasting. In this process, despite food intake, insulin levels are lowered, carbohydrate stores are emptied, and the metabolic state of ketosis is achieved.

Because a ketogenic diet aims for the same benefits as fasting, keto and intermittent fasting are excellent to combine.

By following a low-carb diet, you get a head start on 16/8 intermittent fasting. This way, you don’t have to deplete your glycogen stores first to tap into body fat as a primary energy source.

Even if you break the fast with a meal, you are still in ketosis and, therefore, in a fasting mode.

Hence, the benefits of intermittent fasting 16/8 can be even more significant when you combine it with low-carb or keto:

  • No side effects like headaches, upset stomach, keto flu
  • Better fat burning because you get into ketosis faster with low-carb
  • Constant energy level without switching between burning glucose and fat
Low-carb meals harmonize with 16/8 intermittent fasting

Women and Men

You, too, have probably read that there are unique fasting methods for women, such as crescendo fasting.

This method is nothing more than modified 16/8 intermittent fasting. It involves fasting only every other day and limiting the fasting period to 12 hours.

After that, you extend the fasting period step by step to 16 hours, and finally, you also fast every day.

Moreover, sometimes it is even claimed that intermittent fasting is suitable only for men. Nevertheless, fasting is a natural state our ancestors usually did not choose.

We would not exist today if only the male body were built for it. For this, women, in particular, have had to survive food shortages.

However, hormonal and genetic differences exist between men and women, playing a role in intermittent fasting.

However, the fact that intermittent fasting is fundamentally unsuitable for women is a myth.

Accordingly, a randomized clinical trial in humans did not find different health effects of intermittent fasting for women and men. In this study, the researchers examined (Trepanowski et al. 20174):

  • Blood pressure
  • Blood glucose
  • Insulin levels
  • Insulin resistance
  • Blood lipid levels

These are essential health markers for disease prevention and sustainable weight loss.

Benefits of 16/8 Intermittent Fasting

Intermittent fasting has numerous health benefits proven in many places through studies.

In addition, it affects your life through practical benefits that you may not yet know. Below I have summarized the top 10 benefits of 16/8 intermittent fasting.

1. Autophagy

Although most people start intermittent fasting 16/8 because of weight loss, autophagy establishes probably the most significant health benefit of fasting.

This intracellular recycling system carries damaged, harmful, and toxic compounds out of the body and recycles proteins.

The effect of autophagy is so groundbreaking that it was rewarded with the Nobel Prize in Medicine in 2016 (Levine et al. 20175). 

After stopping food intake for about 14 hours to activate it, you enjoy its benefits daily with the 16/8 method (Yang et al. 20176).

Consumption of carbohydrates, fat, proteins, or even zero-calorie sweeteners, can interfere with autophagy and thus break the fast.

Autophagy can help fight cancer, diabetes, cardiovascular, liver, and autoimmune diseases.

Moreover, because it can slow the aging process, autophagy is arguably the most incredible health benefit of intermittent fasting (Nakamura et al. 20187).

In addition, intermittent fasting 16/8 may prevent neurodegenerative diseases such as dementia, Alzheimer’s disease, and Parkinson’s disease (Raefsky et al. 20178).

2. Weight Loss

With numerous diets, the question arises whether losing weight will work. Intermittent fasting, on the other hand, is different.

When you don’t eat, energy must come from your energy stores. Once the stored carbohydrates are used up, the body burns stored fat for energy (Heilbronn et al. 20059).

In doing so, the body burns unflattering subcutaneous and visceral fat in organs, which is particularly dangerous to health (Catenacci et al. 201610).

3. Savings

One of the enormous benefits of 16/8 intermittent fasting is the positive impact on your daily life.

The food industry loves diet tips that involve multiple meals because no human can cook six times a day. This way, they create a need for more highly processed convenience foods.

Intermittent fasting, on the other hand, is not only cost-effective but also saves you time:

  • No breakfast
  • No expensive exotic superfoods
  • Less processed foods
  • No special recipes
  • No gym subscription

Even though marketing has taught us otherwise, less can be better. You’ll feel it in your checking account.

Intermittent fasting 16/8 saves money on groceries

4. Muscle Gain

16/8 intermittent fasting has been known among bodybuilders for decades as a muscle-building strategy.

Moreover, fasting is the most effective way to stimulate human growth hormone naturally (Ho et al. 198811).

Growth hormone promotes bone, cartilage, and muscle development. As a result, you get more substantial muscles and protection against age-related bone and muscle loss (Rudman et al. 199012).

Accordingly, intermittent fasting combined with appropriate weight lifting helps build and maintain muscle mass.

5. Inflammation

In addition to autophagy, reducing inflammation in the body also contributes to the anti-aging effect of fasting.

Fasting lowers blood sugar and insulin levels, which reduces inflammatory markers and free radicals that cause disease.

Accordingly, a recent study found that lifespan extension significantly benefits intermittent fasting (Catterson et al. 201813).

In addition, numerous studies show that intermittent fasting can lower inflammatory markers contributing to weight gain and insulin resistance (Faris et al. 201214).

6. Insulin Resistance

In particular, our Western diet’s refined carbohydrates and sugars stimulate insulin secretion.

Since too high insulin levels can be life-threatening, the body must protect itself by making cells insulin-resistant. As a result, however, the body must produce more insulin.

In addition to type 2 diabetes, this vicious cycle causes (Ferreira et al. 201815Athauda et al. 201616Herman et al. 201717Orgel et al. 201418Kong et al. 201319):

  • Alzheimer’s disease 
  • Parkinson’s disease 
  • Cardiovascular disease 
  • Cancer 
  • Metabolic syndrome
  • Obesity

Nevertheless, researchers have known for over 50 years that intermittent fasting can combat insulin resistance (Jackson et al. 196920).

Accordingly, a study of over 100 overweight women showed that intermittent fasting over six months could reduce insulin levels by 29% and insulin resistance by 19% (Harvie et al. 201121).

Furthermore, research has recognized intermittent fasting as a safe treatment for insulin resistance (Catenacci et al. 201622).

Some studies suggest intermittent fasting reverses insulin resistance and type 2 diabetes (Halberg et al. 200523).

7. Fertility

Polycystic ovary syndrome (PCOS) is women’s most common metabolic disorder. It characterizes the development of cysts on the ovaries based on hormonal imbalance.

Like type 2 diabetes, obesity, and hypertension are symptoms of PCOS. In short, it is even caused by strong insulin resistance, which increases the risk of diabetes in affected women (Ali 201524).

Nevertheless, in a recent study, intermittent fasting was able to help overweight women with PCOS. As a result, luteinizing hormone release was increased, which helps promote ovulation.

Furthermore, fasting, weight loss, and improved mental health may contribute to fertility (Nair et al. 201625).

Fasting promotes fertility

8. Independence

Intermittent fasting 16/8 positively impacts life by freeing you from letting meals dictate your daily routine.

Intermittent fasting does not require any special knowledge or preparation for beginners. You can start anytime and anywhere by simply skipping a meal.

Intermittent fasting is not a fad diet but an omission. Since fasting is about when you don’t eat, you don’t need new recipes and shopping lists.

9. Cognition

In addition, intermittent fasting can help reduce the accumulation of toxic proteins in the brain that promotes dementia (Li et al. 201726).

Therefore, intermittent fasting may counteract neurodegenerative diseases such as Parkinson’s or Alzheimer’s (Raefsky et al. 201727).

Additionally, fasting increases the brain-derived neurotrophic factor (BDNF), a neuronal growth hormone that increases memory function.

Hence, high levels of BDNF are also associated with increased intelligence. When you release BDNF, the brain can form new neural connections (Witte et al. 200928).

This could be another reason many testimonials speak of increased cognition and heightened awareness of intermittent fasting.

Moreover, in one study, intermittent fasting significantly reduced depression and cravings after only two months, increasing mental health (Hoddy et al. 201529).

10. Gut Health

Periods of fasting give the gut a rest, starve bad gut bacteria, and reduce inflammation.

Thus, according to a recent study, intermittent fasting increases gut health. In this regard, even short periods of fasting at a young age can extend life expectancy (Catterson et al. 201830).

Besides, intermittent fasting has the positive side effect of improving intolerance.

Side Effects of Intermittent Fasting 16/8

Due to the Western diet, many people are accustomed to burning only sugar (glucose) for energy.

Therefore, the initial switch to burning fat for energy through intermittent fasting can sometimes lead to the following side effects:

  • Headache
  • Dizziness
  • Low motivation
  • Nausea
  • Stomach pain

These physical symptoms are also known as the keto flu because the ketogenic diet similarly requires the body to get used to burning fat for energy.

The trigger for this is the depletion of carbohydrate stores. Before the body can enter ketosis, it preferentially consumes glucose from glycogen in the liver and skeletal muscles.

Glycogen is a branched multisugar, with about 2-3 grams of water for every gram of carbohydrate stored.

Physical symptoms- most notably headaches and dizziness- can occur since this causes the body to flush out a considerable amount of water and electrolytes.

However, these disappear permanently once your body is fat-adapted.

Tea and tissues due to flu symptoms

Beginner’s Tips for Intermittent Fasting 16/8

Starting intermittent fasting sounds easy. All you have to do is skip a meal and stop snacking.

However, subtleties often make the difference between weight loss success and failure.

If you understand the following facts about nutrition and daily routine, you will be miles ahead of most intermittent fasting beginners.

When it comes to nutrition, there is a lot of half-knowledge and myths on the web. Hence, intermittent fasting is no exception.

Therefore, beginners should take the following three essential tips to heart to start carefree and without physical side effects into 16/8 intermittent fasting.

1. You Do Not 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 to 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.

Feeling sluggish, the body tells us that readily available energy is running low. But that’s what we want to achieve.

Nevertheless, the body does not immediately expend extra metabolic energy to burn fat, especially if you are starting fasting.

Accordingly, body fat is like a savings account only attacked when the carbohydrate store (the checking account) 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.

Nevertheless, 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, intermittent fasting and muscle-building harmonize for me since fasting releases enormous amounts of growth hormones.

It is important to always exercise within the fasting period to maximize fat burning.

If you eat before exercise, insulin production may prevent fat burning (Meijssen et al. 200131).

2. Stay Hydrated

Especially when you start intermittent fasting, drinking a lot of water is crucial. Otherwise, the fluid loss caused by glycogen depletion will inevitably lead to headaches and other keto-flu symptoms.

Also, drinking is the best cure for cravings. One of the most common beginner mistakes in intermittent fasting is confusing thirst with hunger.

Instead of reaching for water or tea, we go for a snack since solid foods also keep us hydrated.

When we forgo habitual snacks, we don’t automatically replenish the fluids they had previously given us.

As a result, we think we feel hungry. Accordingly, with 16/8 intermittent fasting, especially as a beginner, you often don’t have food cravings but thirst.

Three drinks, in particular, have proven to be effective against cravings:

  • Mineral water: Drinking water before a meal reduces hunger. Carbonic acid also helps with an unsettled stomach. In addition, mineral water contains electrolytes that the body has flushed out when emptying the carbohydrate stores.
  • Black coffee: while caffeine can boost metabolism, the antioxidants in coffee help suppress hunger. For this reason, decaffeinated coffee can also be a good option.
  • Green Tea: Green tea has proven to be a good choice when fasting after being full of polyphenols and other antioxidants. It reduces hunger, stimulates metabolism, and helps with weight loss.

Should we all drink 5 liters of liquid daily during intermittent fasting?

No. Drink when you are thirsty or feel cravings. No one needs to force themselves to drink ill, especially since overhydration can also have side effects.

In addition, fluid needs are individual, so there can be no blanket rule.

In case of doubt, however, a glass of water or green tea will not hurt.

3. Do Not Fear the Shaker

Salt helps against the keto flu

In addition to fluid loss, a second significant aspect is responsible for physical symptoms such as dizziness.

An undersupply of salt (sodium) is the primary trigger of keto flu. Therefore, even in strict autophagy fasting, natural salt is allowed in addition to water.

Along with other electrolytes, sodium, in particular, is flushed out of the body by breaking down carbohydrate stores. Unfortunately, salt still has an unhealthy image unjustly.

However, today we know that it is precisely those nations with the highest salt consumption with the lowest rates of cardiovascular disease (Park et al. 201632).

Moreover, salt takes the bitter taste out of food and acts against cravings. Since it also has a negative feedback loop, unlike sugar, your body will tell you when you’ve had enough salt.

While sugar consumption promotes insulin resistance and body fat storage, salt increases insulin sensitivity and helps with weight loss (Sakuyama et al. 201633).

Finally, salt is the natural antagonist of sugar. If you want to start 16/8 intermittent fasting without problems, salt your food as you like.

In addition, if you have a headache during the fast, you can dissolve natural Himalayan salt in water or drink homemade sole water.

Intermittent Fasting 16/8 Plan

With classic 16/8 intermittent fasting, it’s really up to you which 16 out of 24 hours you decide not to eat.

The only vital aspect, in my experience, is to fit the 8 hours of sleep into the fasting period. This way, you shorten the fast to 8 hours a day. That is only half.

For this reason, it makes little sense to skip lunch. Nevertheless, some people have successfully managed to do this because of their unique daily routines.

However, if you follow a standard 9-to-5 schedule at work, you’ll probably have more success skipping breakfast or dinner.

After most people like to eat in the evening in the company of their loved ones, skipping breakfast has largely proven best.

Intermittent Fasting 16/8 Schedule

Moreover, according to countless experiences, this approach is the most sustainable and easiest way for beginners to start intermittent fasting.

Foods to Eat and Avoid

Although you may eat whatever you want during the 8 hours of intermittent fasting, this will not result in success.

Many people try to fast and then reward themselves with junk food.

You must restrict your carbohydrate intake to lose weight noticeably with intermittent fasting 16/8.

Every time you fill up your glycogen stores, you must burn all those carbs before the body can switch back to burning fat.

As a result, you risk experiencing keto flu symptoms and gaining weight due to water retention.

If you are serious, avoid refined carbohydrates, such as:

  • Bread
  • Pasta
  • Rice
  • Crackers
  • Tortillas
  • Cookies
  • Cakes
  • Pretzels
  • Juices
  • Soft drinks
  • Energy drinks
  • Sweetened tea and coffee drinks

These highly processed foods drive insulin levels to unprecedented heights and promote inflammation and weight gain (Buyken et al. 201434).

After reducing carbohydrates leaves a gap in your daily energy intake, we can fill it with healthy fats.

While carbohydrates stimulate hunger hormones, fats release satiety hormones such as peptide YY, CCK, or leptin (Teff et al. 200435Austin et al. 200936).

Therefore, healthy fats keep you full longer and have been shown to reduce food intake (McLaughlin et al. 199837).

In particular, the best sources of fat include:

  • Coconut oil
  • Coconut milk
  • Extra virgin olive oil
  • Avocados
  • Mackerel
  • Sardines
  • Salmon
  • Anchovies
  • Pastured meat
  • Pasture butter
  • Organic lard
  • Free-range eggs
  • Walnuts
  • Macadamia nuts

Pure fats like olive oil do not stimulate insulin production and interfere with fat burning.

Therefore, you can also do fat fasting if you have trouble fasting for 16 hours. 

For this purpose, high-fat drinks, such as Bulletproof Coffee, Bone Broth, or Golden Milk, have proven effective. 

How Many Calories to Eat

Now that we understand weight gain as a hormonal rather than a caloric imbalance, we must go with the state of science and question the outdated calorie-counting regime.

With this in mind, an empirical study from the United Kingdom shows that 99.5 percent of overweight women and men failed to lose weight successfully through the conventional method (Flides et al. 201538).

We are not talking about three people here, but 99,791 women and 76,704 men!

So why is calorie counting still the standard of the fitness industry?

There are probably three main reasons:

  • The calorimeter was already invented back in 1892
  • Calories are a household word for everyone
  • Highly processed foods are way easier to sell when calorie counting
16/8 intermittent fasting doesn't require you to count calories with a watch

Nonetheless, this does not mean that calorie balance does not affect weight loss. However, proper timing of eating through intermittent fasting 16/8 allows for a significant hormonal benefit.

After insulin levels are low for an extended period during intermittent fasting, you can burn more fat while maintaining your calorie intake.

As long as you don’t cheat or reach your target weight, with 16/8 intermittent fasting, your daily calorie requirement will be enough to lose weight. For a woman, this is about 1,900 kcal.

According to studies, people who eat fewer meals consume fewer calories during the day but usually fall short of the daily requirement (Stubbs et al. 200139).

Finally, 16/8 intermittent fasting is not a conventional diet but a time-based eating pattern.

Breaking Through a Weight Loss Plateau

If you stick to fasting schedules and still have trouble losing weight, unconscious factors could be in your way.

In addition to diet, also lifestyle subtleties can keep you from losing fat:

  • Processed foods: If you prefer industrial products to natural foods, you’re unlikely to succeed – even if they’re labeled “low-carb.”
  • Too many carbohydrates: Although giving up may seem difficult in this age of sugar and side dish addicts, high insulin levels and full glycogen stores prevent fat burning.
  • Soft drinks, juices, shakes, and sports drinks: Beverages are the most common reasons losing weight doesn’t work. They all contain vast amounts of hidden sugar. Moreover, protein shakes stimulate insulin secretion enormously.
  • Sweeteners: Unfortunately, zero sugar does not stand for flawless fat burning, as the advertising teaches us. Common artificial and natural sweeteners increase insulin levels and arouse cravings in the brain’s reward center (Tey et al. 201740Yang 201041).
  • Stress: Psychological stress has been shown to cause fat in the abdomen, thus increasing body mass index and impairing metabolism (Rosmond et al. 199842).
  • Sleep deprivation: Insufficient sleep is one of the most significant stressors. Consequently, a meta-analysis has shown that less than six hours of sleep increases the risk of weight gain by 50 percent (Cappuccio et al. 200843).
  • Excessive exercise: Excessive exercise can cause chronic inflammation and is equally a stressor for the body (Hackney 200644). Moreover, the increased appetite caused by training with the wrong diet will inevitably lead to weight gain.

If you initially have lost some pounds and weight loss stalls after that, you should not despair.

The immediate weight loss is due to glycogen stores depletion and the resulting water weight loss. After that, the body may still need 2-6 weeks to burn fat more efficiently.

Recipes for Beginners

The essential recipes to get you started on intermittent fasting 16/8 are training wheels that can be limited to fats, extend your fast, and supply micronutrients.

Best Bone Broth Recipe (Keto & Fasting)
Whether for fasting, keto, or paleo, you can easily make a nutrient-dense ⚡ power tonic at home with this 🥣 bone broth recipe.
Check out this recipe
Best Bone Broth Recipe (Keto & Fasting)

After the bone broth is full of collagen, healthy fats, and electrolytes, it is an all-purpose weapon for beginners during prolonged and intermittent fasting.

It can help fight headaches, last longer, or replenish the body with essential nutrients when breaking the fast.

7 Amazing Health Benefits of Bulletproof Coffee
Learn how to make epic ☕ Bulletproof Coffee with 🧈 grass-fed butter to maximize your 🧠 health benefits on keto and intermittent fasting!
Check out this recipe
7 Amazing Health Benefits of Bulletproof Coffee

Bulletproof or keto coffee is a drink that sharpens mental focus when you initially struggle to concentrate while fasting.

Since it’s full of healthy fats, it can also replace a meal now and then when you’re short on time.

9 Amazing Golden Milk Benefits Plus Recipe
Reap the benefits of golden milk in no time with this simple recipe: 🌿 Vegan, 🥛 dairy-free, traditional Ayurveda, and even 🥑 keto-friendly.
Check out this recipe
9 Amazing Golden Milk Benefits Plus Recipe

Golden milk is a drink from Ayurvedic medicine known for its anti-inflammatory properties.

The mixture of healthy fats and cinnamon ensures that it will last you longer on intermittent fasting as a beginner.

The Bottom Line

Although many believe fasting could be dangerous, it is natural. In human history, we have been living in food abundance for only the blink of an eye.

With this in mind, we still strive not to stuff food into ourselves every hour. On the other hand, if we give our digestive tract more rest through 16/8 intermittent fasting, we can achieve sustainable health goals, which include:

  • Permanent weight loss
  • Reduced inflammation in the body
  • Improved intestinal health
  • Extended life expectancy
  • Reduced risk of disease
  • Improved mental health

Although 16/8 intermittent fasting is generally considered safe, you should talk to your trusted doctor before doing it if you:

  • Have diabetes
  • Have other blood sugar problems
  • Are taking medication
  • Have low blood pressure
  • Are already underweight
  • Are breastfeeding

In addition, fasting may not be proper in some situations. For example, it can lead to serious health drawbacks under the following conditions:

  • Pregnancy: During pregnancy, the focus is on nourishing and growing your offspring.
  • Chronic stress: If you’re already going through a mentally challenging phase of your life, 16/8 Intermittent Fasting can cause additional stress.
  • Eating disorders: Fasting may not suit you if you develop a questionable relationship with food or have already suffered from eating disorders.

Frequently Asked Questions (FAQ)

How often should you do 16 8 intermittent fasting?

Daily, since breakfast is a habit that will ultimately be unlearned by practicing intermittent fasting 16/8, you won’t be hungry in the morning anymore after 1-2 weeks.

Does 16 8 intermittent fasting really work?

Since it forces the body to empty carbohydrate stores and burns fat, the 16/8 diet can be very effective. The fewer carbohydrates eaten during eating, the more effective it is.

How long does it take for 16 8 intermittent fasting to work?

You will feel the first weight loss within a week when water depots in the body empty. For efficient fat burning, your body may need 3-6 weeks.

How often should you do 20 4 intermittent fasting?

An easy and successful way is to incorporate 20/4 in your work life during the week and switch to 16/8 intermittent fasting on weekends. In any case, I would make intermittent fasting part of my lifestyle.



1Kong 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. 

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. 

3Lustig RH. The neuroendocrinology of childhood obesity. Pediatr Clin North Am. 2001 Aug;48(4):909-30. doi: 10.1016/s0031-3955(05)70348-5. Review. PubMed PMID: 11494643.

4Trepanowski JF, Kroeger CM, Barnosky A, Klempel MC, Bhutani S, Hoddy KK, Gabel K, Freels S, Rigdon J, Rood J, Ravussin E, Varady KA. Effect of Alternate-Day Fasting on Weight Loss, Weight Maintenance, and Cardioprotection Among Metabolically Healthy Obese Adults: A Randomized Clinical Trial. JAMA Intern Med. 2017 Jul 1;177(7):930-938. doi: 10.1001/jamainternmed.2017.0936. PubMed PMID: 28459931; PubMed Central PMCID: PMC5680777.

5Levine 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. 

6Yang JS, Lu CC, Kuo SC, Hsu YM, Tsai SC, Chen SY, Chen YT, Lin YJ, Huang YC, Chen CJ, Lin WD, Liao WL, Lin WY, Liu YH, Sheu JC, Tsai FJ. Autophagy and its link to type II diabetes mellitus. Biomedicine (Taipei). 2017 Jun;7(2):8. doi: 10.1051/bmdcn/2017070201. Epub 2017 Jun 14. PubMed PMID: 28612706; PubMed Central PMCID: PMC5479440. 


7Nakamura S, Yoshimori T. Autophagy and Longevity. Mol Cells. 2018 Jan 31;41(1):65-72. doi: 10.14348/molcells.2018.2333. Epub 2018 Jan 23. Review. PubMed PMID: 29370695; PubMed Central PMCID: PMC5792715. 

8Raefsky SM, Mattson MP. Adaptive responses of neuronal mitochondria to bioenergetic challenges: Roles in neuroplasticity and disease resistance. Free Radic Biol Med. 2017 Jan;102:203-216. doi: 10.1016/j.freeradbiomed.2016.11.045. Epub 2016 Nov 29. Review. PubMed PMID: 27908782; PubMed Central PMCID: PMC5209274. 

9Heilbronn LK, Smith SR, Martin CK, Anton SD, Ravussin E. Alternate-day fasting in nonobese subjects: effects on body weight, body composition, and energy metabolism. Am J Clin Nutr. 2005 Jan;81(1):69-73. doi: 10.1093/ajcn/81.1.69. PubMed PMID: 15640462. 

10Catenacci VA, Pan Z, Ostendorf D, Brannon S, Gozansky WS, Mattson MP, Martin B, MacLean PS, Melanson EL, Troy Donahoo W. A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity (Silver Spring). 2016 Sep;24(9):1874-83. doi: 10.1002/oby.21581. PubMed PMID: 27569118; PubMed Central PMCID: PMC5042570. 

11Ho KY, Veldhuis JD, Johnson ML, Furlanetto R, Evans WS, Alberti KG, Thorner MO. Fasting enhances growth hormone secretion and amplifies the complex rhythms of growth hormone secretion in man. J Clin Invest. 1988 Apr;81(4):968-75. doi: 10.1172/JCI113450. PubMed PMID: 3127426; PubMed Central PMCID: PMC329619. 

12Rudman D, Feller AG, Nagraj HS, Gergans GA, Lalitha PY, Goldberg AF, Schlenker RA, Cohn L, Rudman IW, Mattson DE. Effects of human growth hormone in men over 60 years old. N Engl J Med. 1990 Jul 5;323(1):1-6. doi: 10.1056/NEJM199007053230101. PubMed PMID: 2355952. 

13Catterson JH, Khericha M, Dyson MC, Vincent AJ, Callard R, Haveron SM, Rajasingam A, Ahmad M, Partridge L. Short-Term, Intermittent Fasting Induces Long-Lasting Gut Health and TOR-Independent Lifespan Extension. Curr Biol. 2018 Jun 4;28(11):1714-1724.e4. doi: 10.1016/j.cub.2018.04.015. Epub 2018 May 17. PubMed PMID: 29779873; PubMed Central PMCID: PMC5988561. 


14Faris MA, Kacimi S, Al-Kurd RA, Fararjeh MA, Bustanji YK, Mohammad MK, Salem ML. Intermittent fasting during Ramadan attenuates proinflammatory cytokines and immune cells in healthy subjects. Nutr Res. 2012 Dec;32(12):947-55. doi: 10.1016/j.nutres.2012.06.021. Epub 2012 Oct 4. PubMed PMID: 23244540. 

15Ferreira LSS, Fernandes CS, Vieira MNN, De Felice FG. Insulin Resistance in Alzheimer’s Disease. Front Neurosci. 2018;12:830. doi: 10.3389/fnins.2018.00830. eCollection 2018. Review. PubMed PMID: 30542257; PubMed Central PMCID: PMC6277874. 

16Athauda D, Foltynie T. Insulin resistance and Parkinson’s disease: A new target for disease modification?. Prog Neurobiol. 2016 Oct – Nov;145-146:98-120. doi: 10.1016/j.pneurobio.2016.10.001. Epub 2016 Oct 3. Review. PubMed PMID: 27713036. 

17Herman ME, O’Keefe JH, Bell DSH, Schwartz SS. Insulin Therapy Increases Cardiovascular Risk in Type 2 Diabetes. Prog Cardiovasc Dis. 2017 Nov – Dec;60(3):422-434. doi: 10.1016/j.pcad.2017.09.001. Epub 2017 Sep 25. Review. PubMed PMID: 28958751. 

18Orgel E, Mittelman SD. The links between insulin resistance, diabetes, and cancer. Curr Diab Rep. 2013 Apr;13(2):213-22. doi: 10.1007/s11892-012-0356-6. Review. PubMed PMID: 23271574; PubMed Central PMCID: PMC3595327. 

19Kong 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. 

20Jackson IM, McKiddie MT, Buchanan KD. Effect of fasting on glucose and insulin metabolism of obese patients. Lancet. 1969 Feb 8;1(7589):285-7. doi: 10.1016/s0140-6736(69)91039-3. PubMed PMID: 4178981. 


21Harvie MN, Pegington M, Mattson MP, Frystyk J, Dillon B, Evans G, Cuzick J, Jebb SA, Martin B, Cutler RG, Son TG, Maudsley S, Carlson OD, Egan JM, Flyvbjerg A, Howell A. The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women. Int J Obes (Lond). 2011 May;35(5):714-27. doi: 10.1038/ijo.2010.171. Epub 2010 Oct 5. PubMed PMID: 20921964; PubMed Central PMCID: PMC3017674. 

22Catenacci VA, Pan Z, Ostendorf D, Brannon S, Gozansky WS, Mattson MP, Martin B, MacLean PS, Melanson EL, Troy Donahoo W. A randomized pilot study comparing zero-calorie alternate-day fasting to daily caloric restriction in adults with obesity. Obesity (Silver Spring). 2016 Sep;24(9):1874-83. doi: 10.1002/oby.21581. PubMed PMID: 27569118; PubMed Central PMCID: PMC5042570. 

23Halberg 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. 

24Ali AT. Polycystic ovary syndrome and metabolic syndrome. Ceska Gynekol. 2015 Aug;80(4):279-89. Review. PubMed PMID: 26265416. 

25Nair PM, Khawale PG. Role of therapeutic fasting in women’s health: An overview. J Midlife Health. 2016 Apr-Jun;7(2):61-4. doi: 10.4103/0976-7800.185325. Review. PubMed PMID: 27499591; PubMed Central PMCID: PMC4960941. 

26Li X, Bi X, Wang S, Zhang Z, Li F, Zhao AZ. Therapeutic Potential of ω-3 Polyunsaturated Fatty Acids in Human Autoimmune Diseases. Front Immunol. 2019;10:2241. doi: 10.3389/fimmu.2019.02241. eCollection 2019. Review. PubMed PMID: 31611873; PubMed Central PMCID: PMC6776881. 


27Raefsky SM, Mattson MP. Adaptive responses of neuronal mitochondria to bioenergetic challenges: Roles in neuroplasticity and disease resistance. Free Radic Biol Med. 2017 Jan;102:203-216. doi: 10.1016/j.freeradbiomed.2016.11.045. Epub 2016 Nov 29. Review. PubMed PMID: 27908782; PubMed Central PMCID: PMC5209274. 

28Witte AV, Fobker M, Gellner R, Knecht S, Flöel A. Caloric restriction improves memory in elderly humans. Proc Natl Acad Sci U S A. 2009 Jan 27;106(4):1255-60. doi: 10.1073/pnas.0808587106. Epub 2009 Jan 26. PubMed PMID: 19171901; PubMed Central PMCID: PMC2633586. 

29Hoddy KK, Kroeger CM, Trepanowski JF, Barnosky AR, Bhutani S, Varady KA. Safety of alternate day fasting and effect on disordered eating behaviors. Nutr J. 2015 May 6;14:44. doi: 10.1186/s12937-015-0029-9. PubMed PMID: 25943396; PubMed Central PMCID: PMC4424827. 

30Catterson JH, Khericha M, Dyson MC, Vincent AJ, Callard R, Haveron SM, Rajasingam A, Ahmad M, Partridge L. Short-Term, Intermittent Fasting Induces Long-Lasting Gut Health and TOR-Independent Lifespan Extension. Curr Biol. 2018 Jun 4;28(11):1714-1724.e4. doi: 10.1016/j.cub.2018.04.015. Epub 2018 May 17. PubMed PMID: 29779873; PubMed Central PMCID: PMC5988561.

31Meijssen 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.

32Park 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. 

33Sakuyama 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.


34Buyken AE, Goletzke J, Joslowski G, Felbick A, Cheng G, Herder C, Brand-Miller JC. Association between carbohydrate quality and inflammatory markers: systematic review of observational and interventional studies. Am J Clin Nutr. 2014 Apr;99(4):813-33. doi: 10.3945/ajcn.113.074252. Epub 2014 Feb 19. Review. PubMed PMID: 24552752. 

35Teff KL, Elliott SS, Tschöp M, Kieffer TJ, Rader D, Heiman M, Townsend RR, Keim NL, D’Alessio D, Havel PJ. Dietary fructose reduces circulating insulin and leptin, attenuates postprandial suppression of ghrelin, and increases triglycerides in women. J Clin Endocrinol Metab. 2004 Jun;89(6):2963-72. doi: 10.1210/jc.2003-031855. PubMed PMID: 15181085. 

36Austin J, Marks D. Hormonal regulators of appetite. Int J Pediatr Endocrinol. 2009;2009:141753. doi: 10.1155/2009/141753. Epub 2008 Dec 3. PubMed PMID: 19946401; PubMed Central PMCID: PMC2777281. 

37McLaughlin JT, Lomax RB, Hall L, Dockray GJ, Thompson DG, Warhurst G. Fatty acids stimulate cholecystokinin secretion via an acyl chain length-specific, Ca2+-dependent mechanism in the enteroendocrine cell line STC-1. J Physiol. 1998 Nov 15;513 ( Pt 1):11-8. doi: 10.1111/j.1469-7793.1998.011by.x. PubMed PMID: 9782155; PubMed Central PMCID: PMC2231256. 

38Fildes 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.

39Stubbs 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.


40Tey SL, Salleh NB, Henry J, Forde CG. Effects of aspartame-, monk fruit-, stevia- and sucrose-sweetened beverages on postprandial glucose, insulin and energy intake. Int J Obes (Lond). 2017 Mar;41(3):450-457. doi: 10.1038/ijo.2016.225. Epub 2016 Dec 13. PubMed PMID: 27956737.

41Yang 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

42 Rosmond R, Dallman MF, Björntorp P. Stress-related cortisol secretion in men: relationships with abdominal obesity and endocrine, metabolic and hemodynamic abnormalities. J Clin Endocrinol Metab. 1998 Jun;83(6):1853-9. doi: 10.1210/jcem.83.6.4843. PubMed PMID: 9626108.

43Cappuccio FP, Taggart FM, Kandala NB, Currie A, Peile E, Stranges S, Miller MA. Meta-analysis of short sleep duration and obesity in children and adults. Sleep. 2008 May;31(5):619-26. doi: 10.1093/sleep/31.5.619. PubMed PMID: 18517032; PubMed Central PMCID: PMC2398753.

44Hackney AC. Stress and the neuroendocrine system: the role of exercise as a stressor and modifier of stress. Expert Rev Endocrinol Metab. 2006 Nov 1;1(6):783-792. doi: 10.1586/17446651.1.6.783. PubMed PMID: 20948580; PubMed Central PMCID: PMC2953272.

Mag. Stephan Lederer, MSc.

Mag. Stephan Lederer, MSc. is an author and blogger from Austria who writes in-depth content about health and nutrition. His book series on Interval Fasting landed #1 on the bestseller list in the German Amazon marketplace in 15 categories.

Stephan is a true man of science, having earned multiple diplomas and master's degrees in various fields. He has made it his mission to bridge the gap between conventional wisdom and scientific knowledge. He precisely reviews the content and sources of this blog for currency and accuracy.

Click on the links above to visit his author and about me pages.

Leave a Reply