Intermittent fasting: how to do it, benefits, risks, and experiences

Intermittent fasting: what you need to know before you start

Woman and illustration of intermittent fasting with healthy food and drinking regime, Hemnia logo at bottom right

Fasting has been practised by humans for thousands of years, and some studies suggest possible benefits for metabolism and regeneration. However, fasting is not for everyone – if done incorrectly, it can actually harm the body. In this article, we look at popular types of fasting, the benefits and possible risks, and how to fast properly while respecting your own body. It also includes an interview with Markéta, CEO of Hemnia, who shares her personal experiences with us 💚.

What is fasting and why do we fast?

Fasting is the conscious restriction or complete omission of food for a certain period of time. Some people fast for religious or spiritual reasons, others for health, lightness of body or weight loss.

In recent years, intermittent fasting has become particularly popular – alternating between periods of eating and periods of giving the body a break. However, there are other forms, such as water fasting, where only water is consumed for a certain period of time 💧.

Intermittent fasting: principles and popular methods

Intermittent fasting is a way of eating that involves regularly alternating between periods of not eating and periods of eating. So it's not so much about what we eat, but rather when we eat ⏱️.

The 16/8 fasting method

The most common form is to extend the fasting period during the day – for example, 16 hours without food and an 8-hour window for eating (the 16/8 method). Usually, breakfast or dinner is skipped to create a longer break between meals.

In practice, this method is the most popular because it is easy for most women to manage and fits naturally into the day.

For example, you have dinner at 6 p.m. and don't eat again until around 10 a.m. the next morning. Within the 8-hour "eating window", you can then divide 2-3 meals according to what suits you.

Compared to stricter options, this rhythm seems more sustainable and less stressful – and long-term sustainability is key for such regimes 💚.

Other popular methods

Other fasting options include:

  • 5/2 regime: Five days a week you eat as usual, and on two (non-consecutive) days you significantly reduce your calorie intake, usually to around 500-600 kcal per day.
  • Alternate-day fasting: You fast or eat very little every other day, and in between you eat as usual.
  • One-day fasting: For example, a 24-hour fast once a week or occasionally as needed, then return to your normal diet.
  • OMAD ("one meal a day"): A more extreme form, where you eat only one larger meal during the day and fast the rest of the time.

 

Intermittent fasting 16/8 – illustration of a healthy plate and fruit as part of a balanced diet during intermittent fasting, Hemnia logo at bottom right

Health benefits of fasting

Many people are interested in fasting mainly because of its potential health benefits. The most common goal is weight loss, but research suggests other positive effects as well.

With intermittent fasting, you will often naturally consume fewer calories, which can lead to gradual weight loss. Studies report an average decrease of around 0.25 kg per week if you stick to the regime.

It is also interesting to note that many women report feeling less hungry in the evening. Hormone levels associated with appetite (such as ghrelin) may stabilise over time, making fasting easier for the body to tolerate.

In addition to weight loss, other positive changes in health indicators have been observed with fasting.

📚 Possible benefits according to studies:

  • lower blood pressure
  • reduction in oxidative stress (which damages cells and contributes to ageing and lifestyle diseases)
  • improved insulin sensitivity
  • more stable blood sugar levels
  • decrease in blood fats and LDL ("bad") cholesterol
  • possible link to lower risk of heart disease and type 2 diabetes

💡 Autophagy – cellular "recycling": During prolonged fasting, cells switch to a more economical mode and remove damaged or unnecessary parts. This process may be responsible for some of the regenerative effects of fasting. (Research on autophagy was awarded the Nobel Prize in 2016.)

Risks of fasting and who should avoid it

Although fasting can be beneficial for healthy adults, it is not suitable for everyone. Side effects (intense hunger, irritability, headache, dizziness or fatigue) may occur, especially at the beginning. It is important to ensure adequate fluid intake.

❌ Fasting is generally not recommended for:

  • pregnant and breastfeeding women
  • children and adolescents
  • people with eating disorders
  • diabetics without medical supervision
  • cancer patients and people with serious illnesses
  • seniors (due to the risk of muscle loss)

Caution is also necessary when taking medication for blood pressure or other chronic conditions.

If you are unsure whether fasting is safe for you, ask your doctor 👩‍⚕️.

Fasting and the female body: what you need to know

The female body may react differently to fasting than the male body, mainly due to hormonal changes 🌸. In women of reproductive age, overly strict fasting can act as a stress signal and disrupt the hormonal balance in some.

This can manifest itself, for example, in:

  • irregular menstruation or missed periods
  • fatigue, irritability or mood swings
  • hot flashes or general discomfort

Therefore, women are often advised to start cautiously and choose milder regimes (for example, 12-14 hours of fasting instead of 16+). The main thing is to monitor how your body reacts and not to overdo it, especially in the period before menstruation, when the body is more sensitive.

🤰 Fasting is generally not recommended during pregnancy and breastfeeding, as the need for nutrients is increased during this period.

After menopause, hormonal fluctuations no longer play such a big role, but even then it is important to ensure that you have enough protein and a generally high-quality diet.

 

Intermittent fasting – plate, clock, and healthy foods as part of a balanced diet, Hemnia logo at bottom right

How does fasting affect weight loss?

The most common reason women try fasting is to lose weight. Intermittent fasting can facilitate weight loss simply by reducing the time spent eating – and thus often the total energy intake.

For example, if we skip evening snacks, we naturally consume fewer calories than if we snack throughout the day.

📚 Research shows that intermittent fasting is as effective for weight loss as traditional calorie restriction. Weight loss is mainly due to eating less, not because fasting causes some kind of special "magical fat burning".

📚 Some studies even suggest that if calorie intake is the same, fasting may not be more effective than the usual even distribution of meals throughout the day.

💡 Simply put, fasting can be a useful tool, but the key is still total energy intake and long-term sustainability.

From a practical point of view, however, many people find fasting more convenient than constantly counting calories. For some, it is easier to skip meals for a few hours than to watch their portions all day long.

However, it is very individual – while some women feel great on the 16/8 regime and do not feel the need to "catch up", others may tend to compensate for everything in the eating window with larger portions or caloric rewards.

In such cases, the weight loss effect can easily diminish. That is why it is necessary to think about the quality and quantity of food we consume during the day, even when fasting, and to give our bodies exactly the amount of energy they really need 🧘‍♀️.

How to do it, or how to fast properly

If you are new to fasting, take it slowly and without pressure. The key is to find a regime that is sustainable in the long term.

  • Start simple: Try a 12-hour fast overnight (e.g. from 8 p.m. to 8 a.m.). For most people, this is a natural and easy start.
  • Gradually extend the interval: Once your body gets used to it, you can add an extra hour, for example. Gradually, you will reach a 16/8 routine.
  • Listen to your body: If you experience severe weakness, dizziness, extreme hunger or irritability, slow down or stop fasting. Your body always gives you signals.
  • Stay hydrated: During fasting, drink water, unsweetened teas and, if necessary, black coffee without sugar or milk. Sweetened drinks or juices interrupt fasting.
  • Stay active: Light exercise such as walking or yoga is fine. It is better to plan more strenuous training for when you are eating and replenishing your energy.
  • Eat a balanced diet on "eating days": When you are not fasting, try to eat a healthy and balanced diet. Fasting does not mean that you can eat anything without restriction – on the contrary, your body needs to replenish proteins, vitamins and minerals.
  • Don't forget protein: It is especially important to consume enough protein to prevent muscle loss. With fewer meals, it is easy to fall short of the recommended amount (about 1 g of protein per kg of body weight). Each meal should therefore contain a high-quality source of protein (fish, eggs, lean meat, legumes or dairy products).
  • End your fast gently: After prolonged fasting, do not start with heavy, sweet or fatty foods. It is best to eat something small first, such as broth or a few nuts, and then a full meal after 15-30 minutes.
  • Choose a balanced meal after fasting: Focus on a combination of protein, fibre and healthy fats to avoid a sharp spike in blood sugar.
  • Eat slowly and calmly: Your body needs to get used to eating again after fasting. Gorging on food can cause unpleasant digestive problems.
  • Consider consulting a professional: Before embarking on more extreme forms of fasting, consult your doctor or nutritionist, especially if you have health problems or are taking medication. A professional will help you set up a regimen that is safe and sustainable in the long term.

Intermittent fasting experience: interview with Markéta, CEO of Hemnia

Markéta Novák Matějková is the CEO of Hemnia, a mother of four, and a Tabata and Pilates instructor. She has tried intermittent fasting herself and shares her experiences with us in this interview. She speaks openly about how she combines business, family, and an active lifestyle.

 

Markéta Novák Matějková, founder of Hemnie – intermittent fasting experiences and an active lifestyle

What led you to try intermittent fasting? Did you have any specific motivation to start fasting?

Yes, my motivation was my mum, who started intermittent fasting and praised it. My motivation was probably to lose a few kilos. I run regularly and thought I might feel lighter.

What fasting regime did you choose and how long did you stick to it?

At first, I was strict and did it every day, eating for 10 hours and fasting for 14. The problem for me was that I get up very early and am used to eating breakfast, so I would finish eating at around 3:30 p.m.

What did your typical day look like during intermittent fasting? Which meal of the day did you skip and how did you feel physically and mentally?

I skipped dinner. Mentally, I felt fine, but physically it was sometimes difficult because I do a lot of sport. In the end, it turned out that coming home from training and not eating was not a good idea.

Was it difficult to get used to the new eating rhythm? What were the biggest challenges you had to overcome, especially in the beginning?

Not really, but the biggest problem was the hunger I felt after evening training.

Did you notice any changes in yourself during the fasting period?

Yes, my weight went down, but slowly, which suited me. I would also say that I had more energy in the evening.

Did you have to adjust your diet during the fast?

I didn't change my diet. I think I've been eating a balanced diet my whole life. I've never overeaten, and I have the advantage of not liking sweet drinks, crisps or fried foods. I also monitor my vitamin intake, so that wasn't a problem. The only thing I've been paying more attention to lately is my protein intake.

Did fasting have any impact on your working day and performance? As a CEO, you have a demanding schedule – was it difficult to combine your work responsibilities with a period of not eating?

It wasn't difficult at all because I stopped eating when I was at home.

The only problem was that, as I am active in the afternoon, I was sometimes hungry in the evening. And that was the stumbling block. That's why I don't do intermittent fasting every day now, but only two days a week, for example. From my experience, however, I can say that you feel lighter and your mind is clearer.

How did those around you react to your fasting? How did you deal with situations such as family dinners?

No one made a fuss about it. I just cooked for the family and didn't eat dinner, which wasn't surprising because I often eat different meals than my children.

They probably wouldn't be thrilled about avocado or millet porridge for dinner. And my husband took it completely normally, because it wasn't anything extreme.

Would you recommend intermittent fasting to other people around you? What advice would you give to someone who is thinking about fasting and is a complete beginner?

I think it's worth trying, and if someone wants to manage their weight, I think it's an ideal and healthy way to lose weight.

I would start gradually and not drastically, eating only for a few hours and then fasting. It also depends on what your daily routine is like. There is definitely no ideal guide for everyone.

Some people sleep longer but work late into the night, so they can afford to eat later and have their last meal in the evening. I get up at 5 a.m., so if I want to fast for 14 hours, I should ideally finish eating after 3 p.m., because I usually have breakfast shortly after waking up. It's not for everyone.

Do you plan to continue fasting in the future? Are you considering other options, such as a longer water fast? What has this experience given you personally?

I'm not tempted by a longer fast at the moment, but I'm not ruling it out. Otherwise, it definitely gave me the insight that when you don't burden your digestion so much, you really feel better and your mind is clearer. It's nothing groundbreaking, but the difference is really noticeable.

Did any Hemnia products help you during the fast?

I didn't use anything extra that I hadn't used before. I use CBD products, collagen, our green drink and creatine every day, so there was no need to add anything else.

What would you recommend to someone who wants to make fasting as pleasant as possible?

Don't overdo it. Try it, stick with it for a while, but if you find that it's not for you, don't worry about it and set up a routine that suits you.

I'm not a fan of forcing things. I think everyone should ask themselves why they're doing it and whether it suits them. When we're motivated, everything is easier. And definitely don't do it just because it suits your friend.

My mum has been intermittent fasting for over six months and can't praise it enough, but it's also worth mentioning that she has a different lifestyle and spends her afternoons relaxing. Meanwhile, I'm under a lot of mental pressure because I pick up and drive my children to their afternoon activities, have evening classes at the gym, and cook dinner for the next day in the evening, so it's logical that I need a little energy boost in the evening.

But what I found to be an advantage was that every evening I looked forward to breakfast, which I was able to enjoy and definitely didn't just settle for a sweet bun. It's definitely worth a try 😊. 

 

Markéta Novák Matějková on the road – intermittent fasting, experiences, and the active lifestyle of the founder of Hemnia

Intermittent fasting: always with respect for yourself 💚

Fasting can be a functional tool for some, a dead end for others. It is not a universal solution or a shortcut to health, but one of the ways to work with your regime and relationship with food.

As Markéta's experience shows, it is important to find a rhythm that fits into your life – not the other way around.

If fasting makes you feel lighter, more focused and suits you in the long term, it can be a useful addition to a healthy lifestyle. If not, that's fine too. Health is not based on a single method, but on a balance   – between eating and pausing, performance and rest, discipline and kindness to yourself 🧘‍♀️💚.

FAQ

1. Does intermittent fasting differ according to age?

Yes ✔️. Expert sources point out that intermittent fasting is not suitable for all age groups. Fasting is not usually recommended for children and adolescents because they are in a growth phase and need more energy and nutrients.

Caution is advised for older adults due to the risk of insufficient protein intake and possible loss of muscle mass.

2. Is fasting therapeutic?

Fasting is not a panacea or a guaranteed "cure" for disease.

Some research suggests possible health benefits, but fasting should never replace professional care or a balanced diet. It can be a useful tool if you approach it in an informed manner, with respect for your body and without unnecessary pressure.

3. What is water fasting?

Water fasting means that you consume nothing but pure water 💧 for a certain period of time. It usually lasts 1-3 days and should not exceed 72 hours without medical supervision.

In the short term, it can trigger processes such as fat burning (ketosis) or autophagy. At the same time, however, it is one of the most demanding forms of fasting and carries risks – for example, a significant drop in blood pressure, mineral imbalance or complications when returning to eating.

❌ Water fasting is not suitable for pregnant and breastfeeding women, children, people with diabetes, gout or eating disorders.

If you are considering it, it is advisable to consult your doctor 👩‍⚕️ and return to eating very gradually.

4. What is a one-day fast?

A one-day fast (often referred to as a "24-hour fast") means that you do not eat for 24 hours – it is commonly practised from breakfast to breakfast or from lunch to lunch.

During the fasting period, non-caloric beverages such as water, tea or black coffee ☕ are usually allowed.

5. What should a meal plan for intermittent fasting look like?

There is no "special" diet just for fasting – even during the eating window, it is recommended to follow the usual principles of a balanced diet.

In practical terms, this means:

  • nutritious meals (not "catching up" on hunger)
  • lots of vegetables and fruit for nutrients
  • a balanced plate across the main food groups

6. How does fasting affect blood tests?

Short-term fasting can affect certain blood values, which is why fasting is recommended for certain tests. This most often applies to sugar levels (glycaemia) and lipid profiles (especially triglycerides).

"Fasting" usually means 8-12 hours without food, with only plain water allowed to drink. Coffee, tea or other beverages may skew the results unless otherwise instructed by your doctor.

However, not all blood tests require fasting – it is always best to follow the instructions of your doctor or specific laboratory 👩‍⚕️.

7. Does fasting help detoxify the body?

Fasting is often associated with detoxification, but expert sources point out that the body has its own detoxification system – the liver and kidneys play a major role in continuously breaking down waste products. Therefore, a healthy person does not need a special detoxification treatment.

Some research is investigating whether fasting can affect cellular processes such as autophagy, but it cannot yet be said that fasting works as a universal "cleansing" of the body.

💡 Fasting is not a proven detox, but it may have other metabolic effects.

8. How can you tell if fasting is good for you?

Fasting is not a universal recipe for health or weight loss, but it can be beneficial for some women.

Research shows that intermittent fasting can promote weight loss and improve certain health indicators – largely because we consume less energy overall and often adjust other habits as well.

However, the basis remains a balanced diet and regular exercise 🥗🤸‍♀️. Fasting can complement these, but not replace them. If you are healthy and this regime suits you, it can be one way to better manage your calorie intake and support your metabolic health.

However, it is not a miracle method – the positive effect only lasts if the regime is sustainable in the long term. Once you return to an unhealthy diet, the results usually disappear quickly.

Before you start fasting, always consider your individual situation – and if you are unsure, consult a professional.

 

Sources:

  

Author: Patricie Mikolášová

 

Foto: AI

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