Even if you're only vaguely interested in health and nutrition, you've probably heard of intermittent fasting, right? This eating trend has become hugely popular in recent years and, unlike crash diets with their yo-yo effect, it is praised as a simple and effective way to lose weight and improve your health. But what exactly is behind the idea of intermittent fasting? What are the rules and restrictions?
In this article we take a deep dive into the world of intermittent fasting to find out what is allowed and which principles guide this fasting routine. Whether you already have experience with intermittent fasting or are just thinking about it, this information will help you understand the basics and make the right choices for your own diet.
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Introduction to intermittent fasting
What is intermittent fasting and how does it work?
Intermittent fasting is a special form of fasting. You don't give up food completely, only during a certain time window. That means there is a set period when you can eat, and in the phase that follows you stay fasted and only have water and other calorie-free drinks.
There are different ways to divide up your eating and fasting periods, so you can pick the type of fasting that suits you best.
Popular methods of intermittent fasting
Intermittent fasting: the 16:8 method
16 hours of fasting - 8 hours of eating. That's the principle of 16:8 intermittent fasting. You can choose the eating window yourself. So if you're not a breakfast person, an eating window from 12:00 to 20:00 is a good option, for example. During the fasting phase no calories should be consumed. You can drink water, tea or black coffee.
Intermittent fasting: the 5:2 method
With the 5:2 method you fast on two days a week and eat normally on the other five days. Fasting here means limiting your calorie intake to a maximum of 500 calories for women and 600 calories for men.
The comparison: intermittent fasting 16:8 vs. 5:2
The advantage of the 5:2 method is that the longer fasting phase of two days leads to stronger autophagy than with the 16:8 method. However, the 5:2 method is also harder to fit into a busy daily life - especially if you do physically demanding work. So decide for yourself which of the two methods of intermittent fasting suits you and your routine better.
Intermittent fasting: the benefits
Weight loss and better metabolism with intermittent fasting
Intermittent fasting can lead to you eating fewer calories over the day. The shorter eating windows limit the times when you take in food, which lowers the chance of overeating and can create a natural calorie deficit, which in turn can lead to weight loss. Because your body isn't supplied with food continuously during the fasting periods, it starts to draw on stored fat reserves for energy. This increases fat burning, which also contributes to weight loss. Over time, your body also adapts to fasting, which can lead to more efficient use of the available energy sources.
Heart health and blood sugar control with intermittent fasting
Cellular recycling and autophagy
During fasting, cellular cleaning processes such as autophagy (cell repair and removal of damaged cells) can be activated. This may improve cell health and possibly lower the risk of age-related conditions.
Better hunger management with intermittent fasting
Some people report that intermittent fasting has helped them understand their hunger better and eat less impulsively and more mindfully. By contrast, many people say that conventional diets actually made their cravings worse. The fasting periods give you the chance to plan your next meals within your eating window in a relaxed way.
Hormonal adjustments and insulin sensitivity with intermittent fasting
Intermittent fasting can cause changes in hormones such as insulin, glucagon, leptin and ghrelin. These hormones influence appetite, metabolism and energy balance. Intermittent fasting may also increase insulin sensitivity, which means your cells respond to insulin more efficiently and your blood sugar level stays more stable. This may help lower the risk of type 2 diabetes.
These are the eating rules for intermittent fasting
With the intermittent fasting method, also known as "alternate day fasting", there are certain eating rules and recommendations to get the best results and stay in a fasted state. Here are some of the most important eating rules for intermittent fasting:
With this way of eating, set your eating window, which is the time during the day when you have your meals. This window should match the intermittent fasting method you chose, e.g. 16:8, 18:6, 5:2 or another one. During the eating window you can have meals and snacks, while during the fasting period you go without food.
During the fasting period you should have no solid food, snacks, drinks with calories or alcohol. This means you shouldn't eat meals or snacks and should stick to calorie-free drinks such as water, unsweetened tea or black coffee without sugar or milk.
Make sure you keep an eye on portion sizes during the eating window and keep your diet balanced. Intermittent fasting is not an excuse to overeat in everyday life.
During the eating window, choose healthy, nutrient-rich foods that fit your personal nutrition goals. That means you should focus on protein, fruit, vegetables, wholegrain products and healthy fats rather than highly processed foods, sugary snacks or junk food, to get lasting results.
Drink enough water to stay hydrated while fasting. Water is an important building block for avoiding dehydration and keeping your metabolism going.
Enough good-quality sleep is important to support the fasting process during your fasting cleanse. A regular sleep cycle can help regulate your hormone balance and control your appetite.
Physical activity can help boost your metabolism and promote fat burning, which can help with losing weight in the long run. Adapt your training to your fasting routine and make sure you have enough energy for your activities.
Keep in mind that intermittent fasting doesn't work the same for everyone. You can adjust the method to your individual needs and preferences. Some people prefer longer fasting periods, while others prefer shorter ones. Listen to your body and make adjustments if needed.
Before you start intermittent fasting, it's wise to talk to a doctor or nutrition expert to make sure it suits your individual health goals and needs and to get more valuable tips. Following these eating rules can be a reason to get the most out of the benefits of intermittent fasting and support your health.
Mistakes in intermittent fasting - what can I get wrong with intermittent fasting?
Whether it's the 16:8 method, where you eat for eight hours a day and fast for the other 16, or the 5:2 method, where you fast on 2 days a week and eat normally on the other 5: with every variant of fasting cleanses there are rules you should stick to, so you reach your goals and don't just blindly run after a trend.
With intermittent fasting there are some common mistakes you should avoid to get the best results and not put your health at risk. Here are some of the most common mistakes in intermittent fasting:
Overeating during the eating window
A common mistake is eating too much during the eating window to make up for the hunger built up in the fasting phase. This can lead to a calorie surplus and cancel out the potential benefits of fasting. It's important to watch portion sizes and keep your diet balanced.
Unhealthy eating during the eating window
Intermittent fasting doesn't mean you can eat whatever you like during the eating window as long as it fits the time slot. An unhealthy diet with lots of sugar, processed foods and saturated fats can cancel out the positive effects of fasting on your health. It's important to keep paying attention to a balanced diet.
Fasting too often
Some people tend to practise intermittent fasting too often, by fasting every day or choosing fasting periods that are too long. This can lead to a lack of nutrients and energy. It's wise not to practise intermittent fasting every day and to take breaks now and then. Find out for yourself how long the 'recycling programme' is good for you and your body, and don't fast for more than 7 days in a row without medical supervision.
Not drinking enough during intermittent fasting
During the fasting phase it's important to drink enough fluids to stay hydrated. Nothing is more important than drinking plenty of water, unsweetened tea and coffee without calories to avoid dehydration.
Ignoring your individual needs
Everybody is different, and what works for one person may not work for another. It's important to listen to your own body's needs, get a picture of how you're doing and make adjustments if necessary.
Overdoing the training
Intense training during the fasting phase can be challenging for some people and lead to exhaustion. It's wise to adapt your training accordingly and make sure you have enough energy. Do you have questions on this topic? Then click the link and read our blog article on exercise while fasting.
Not listening to your body
If you feel unwell during intermittent fasting, you should listen to your body and, if needed, talk to a doctor or nutrition expert. Fasting should never lead to strong physical or emotional strain.
What is allowed during fasting and eating phases?
Foods allowed during the eating phases
With intermittent fasting there are certain foods and drinks that are allowed during the eating window. In general, during this time you can eat most of the foods you would also eat in a normal, balanced diet. Here are some examples of foods that are allowed during intermittent fasting:
Protein during intermittent fasting
Lean meat (such as chicken, turkey breast, beef, fish), tofu, tempeh, legumes (such as beans, lentils) and eggs.
Vegetables during intermittent fasting
All kinds of vegetables are allowed. The more colourful and varied, the better, since different vegetables contain different nutrients.
Fruit during intermittent fasting
Fresh fruit is a healthy choice, but it should be eaten in moderation because it contains sugar. Go for whole fruit rather than juices.
Wholegrain products during intermittent fasting
Wholegrain bread, wholegrain pasta, brown rice, oats and other wholegrain products are a good source of fibre and long-lasting energy.
Healthy fats during intermittent fasting
Avocados, nuts, seeds and olive oil are rich in healthy unsaturated fatty acids and can be part of a balanced diet.
Dairy during intermittent fasting
If you tolerate dairy, low-fat or fat-free options such as yoghurt, cheese and milk are allowed. Alternatives such as almond, soy or oat milk are also an option.
Drinks during intermittent fasting
Water is the best choice and should be drunk in sufficient amounts to stay hydrated. Unsweetened tea and coffee without calories are also allowed during the fasting period. You can also reach for light or diet drinks, but these should be consumed in moderation.
Keep in mind that - even if these foods are allowed during the eating window - portion sizes and total calorie intake still matter. We advise you to keep your diet balanced and avoid eating too many sugary foods, highly processed foods and saturated fats.
If you have special dietary needs or preferences, feel free to adapt intermittent fasting to your individual wishes. Make sure you get enough nutrients during the eating window to support your health.
Intermittent fasting: which drinks are allowed on fasting days?
During the fasting period of intermittent fasting you should not take in any calories, so you stay in the fasted state. That means you shouldn't have solid food, snacks or drinks with calories during this time.
Water during intermittent fasting
Water is essential for general health and wellbeing. During the fasting phase you may lose water through sweating, breathing and urinating. That's why it's important to drink enough water to prevent dehydration.
Drinking water can help reduce hunger pangs during the fasting period. Thirst and hunger are often mixed up. If you feel hungry, it can help to drink a glass of water first and see if the hunger fades.
Water is needed for many basic body functions, including metabolism. Drinking enough water helps you keep your energy level up, which is especially important while fasting.
Water also plays an important role in digesting food and removing waste products from the body. Enough fluids support digestive functions and help the body get rid of toxins.
Drinking water can also help keep your blood sugar level stable by supporting the body in removing excess glucose from the blood.
Dehydration can have a negative effect on your cognitive function. Drinking enough water can help maintain concentration and alertness.
During the fasting period it's important to make sure you stay well hydrated. You can sip water in small amounts throughout the day to make sure you stay well hydrated. Besides water, unsweetened herbal teas and black coffee without sugar or milk are also allowed drinks during intermittent fasting.
Unsweetened tea during intermittent fasting
Tea is mostly water and contributes to hydrating the body. During the fasting period it's important to stay well hydrated to avoid dehydration.
Tea, especially herbal tea or green tea, can help reduce hunger pangs during the fasting phase. Warm tea can create a pleasant feeling of fullness and temporarily curb the desire for food.
Some studies suggest that tea, especially green tea, may boost metabolism and promote fat burning. This can be helpful for weight management and fat reduction during intermittent fasting.
Herbal teas such as peppermint tea or ginger tea help some people with digestion and may ease digestive discomfort.
Tea can be a welcome change from water, especially when you crave flavour without adding extra calories. Make sure to drink your tea without sugar or milk, as these can contain calories.
According to some studies, certain teas such as chamomile or lavender tea can have a calming effect and help reduce stress and tension. This can be especially useful while fasting, to prevent stress eating.
It's important to note that tea without calories should be consumed during the fasting period. If you add sugar, honey or milk to your tea, this can break the fasted state and kick-start calorie intake. Unsugared and unsweetened teas are therefore the best choice if you want to drink tea during intermittent fasting.
Coffee without calories during intermittent fasting
The caffeine in coffee can help suppress appetite and reduce feelings of hunger, which can help you get through the fasting period more easily.
The caffeine in coffee is known for improving alertness and concentration. While fasting, coffee can help reduce signs of fatigue and tiredness.
If you like the taste of coffee, it can be a pleasant change from water without adding extra calories. Choose black coffee without sugar or milk, though, so you don't break the fasted state.
It's important to drink coffee in moderation and not overdo it, as too much caffeine can cause side effects such as sleep problems, a racing heart and nervousness. Individual tolerance to caffeine varies, so it's wise to pay attention to your body's signals and watch how coffee affects you.
Sparkling mineral water during intermittent fasting
Drinking sparkling water during intermittent fasting can offer some benefits, depending on your individual preferences and needs.
Sparkling water can be a welcome change from still water, especially when you're looking for something fizzy and refreshing. This can help make drinking more enjoyable.
The carbonation in sparkling water can help boost the feeling of fullness and temporarily reduce appetite. This can be especially useful during the fasting period.
Some people find that sparkling water can help with digestive discomfort such as bloating or a feeling of fullness. It can help release gas from the digestive tract.
Sparkling water is still an excellent source of hydration and can help prevent dehydration while fasting.
It's important to note that sparkling water normally contains no calories or carbohydrates, as long as no extra flavourings or sweeteners are added.
Chewing gum: allowed during intermittent fasting or not?
The question of whether chewing gum is allowed during intermittent fasting is a bit more complex, as it depends on various factors and is debated.
If you chew calorie-free gum without sugar or calorie substitutes, it normally shouldn't disturb the fasted state. This kind of gum usually contains no significant calories and can help keep your mouth fresh and reduce the desire to eat during the fasting period.
Sugary chewing gum is generally not allowed during fasting, as it contains calories and carbohydrates that can raise blood sugar and would break the fasted state.
Some chewing gums can contain artificial sweeteners or other additives which, although calorie-free, can trigger insulin responses in some people. It's recommended to avoid gum with such additives if you want to be sure you stay in the fasted state.
Chewing gum can make you swallow air, which can lead to bloating or stomach discomfort. Some people may not tolerate chewing gum well while fasting.
Intermittent fasting: is broth allowed or not?
Yes, broth, especially clear broth or vegetable broth, can be allowed during intermittent fasting in many cases and can even offer some benefits.
Clear broth or vegetable broth normally contains only a few calories, especially if no extra ingredients such as oil or noodles are added. This lets you stay in your fasted state while drinking something warm.
Broth is mostly water and contributes to hydration, which is important during fasting to avoid dehydration.
Broth can help boost the feeling of fullness, especially if you feel hungry while fasting. The warm, salty taste can temporarily curb your appetite.
Broth often contains sodium and other electrolytes that can be lost during fasting. Drinking broth can help keep your electrolyte balance in check.
It's important to make sure the broth doesn't contain large amounts of fat, carbohydrates or calories. If you make broth yourself, you can control the ingredients and make sure it fits your fasting goals.
Are drinks with sweeteners allowed during intermittent fasting or not?
Using drinks with sweeteners during intermittent fasting is a controversial topic and depends on various factors, including personal preferences and goals. Here are a few things to consider:
Many sweeteners are calorie-free and contain no carbohydrates, which means that in theory they shouldn't break the fasted state, as they have no significant effect on insulin levels. Some examples of calorie-free sweeteners are stevia, aspartame, saccharin and sucralose.
Some people prefer the taste of sweetened drinks or find them helpful to make their fasting period more pleasant. Adding sweeteners can make drinks like tea, coffee or water tastier without adding extra calories.
Drinks with sweeteners can be an alternative to avoid sugary drinks during fasting, since sugar contains calories and can raise blood sugar.
Some studies suggest that consuming sweeteners in large amounts can increase appetite and the craving for sweet foods. This could lead to you eating more during the eating period.
Keep in mind that your individual response to sweeteners can vary. Some people tolerate them well and see no negative effects on their fasting experience, while others may find that sweeteners stimulate their appetite or cause digestive problems.
5:2 method - intermittent fasting with frank.
The 5:2 method is a particularly flexible type of intermittent fasting where you fast for 2 days and eat normally for 5 days a week, making it easy to reduce weight. You can freely choose your two fasting days per week and also decide whether you want to fast the 2 days in a row or separately from each other.
The 5:2 intermittent fasting programme from frank. gives you everything you need to get started! Here's a quick overview. For each fasting day you get three dried meals as main meals, a ginger shot, plus herbal tea. The meals serve as breakfast, lunch and dinner and are split into muesli, vegetable stir-fry and soup. They are fairly low in carbohydrates and keep you particularly full thanks to fibre, protein and high-quality fats.
On top of that you get our premium protein powder with a shaker, so you can make tasty protein shakes as meal replacements on your other 5 days. The extensive guide that comes with the programme gives you information and tips for your everyday life, plus plenty of recipes to follow.
A 5:2 intermittent fasting programme lasts 4, 8 or 12 weeks, depending on the length you want. This sets the programme clearly apart from a crash diet and supports you in reducing your body weight sustainably.
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Conclusion
To wrap up, intermittent fasting is more than just a short-lived trend. It offers a flexible, everyday-friendly way to improve your health and manage your weight at the same time. Whether you go for the 16:8 or the 5:2 method, the key is to find a routine that fits your lifestyle.
Make sure you eat healthy, balanced meals during the eating phases and stick to the fasting rules consistently. Listen to your body, adjust your fasting methods if needed, and don't forget that enough fluids and sleep are just as important as the fasting itself. If you follow these tips, you can make the most of the benefits of intermittent fasting. Good luck on your way to a healthier you!
