Water fasting
During an X period, only pure water is consumed, with the aim of giving the body and mind the opportunity to reset, recover and regenerate. It is a process of deep cellular cleansing, hormonal recalibration and mental clarity, activating the body's self-healing capacity.
Fasting: a natural reset for body and mind
We live in a time when food is everywhere. Advertisements, smells, photos of meals, flavourings, colours, supermarket promotions — everything is designed to make us eat, all day long.
We hear that breakfast is the most important meal of the day (which is not a lie when taking in the TCM perspective), preferably with a bowl of sugar-filled cornflakes. Water must have flavour, otherwise we find it too boring. And in winter, we still want to be able to eat strawberries, just because we can.
As a result, our senses are constantly “on”. We taste, smell and crave — often not because we are hungry, but because we are stimulated. Our bodies hardly get a chance to recover.
In the past, people fasted out of necessity, because there simply wasn’t always food available.
Today, it’s the other way around: we have abundance, but as a result, we no longer have natural breaks.
Yet our bodies still need those moments of rest.
By fasting, you break through the constant stream of stimuli and temptations.
You are saying, as it were: “For a moment, nothing but listening to what my body really needs — to recover, to detoxify, to regenerate. A natural reset, not only for your body, but also for your mind.
Types of fasting
There are different types of fasting, each with its own intensity and purpose:
- Intermittent fasting (time-restricted eating): you eat within a fixed time window, for example 8 hours a day, and let your body rest for 16 hours.
- Fasting every other day or 5:2: occasionally a day with very few calories or only water and tea.
- Longer water fasting (this is the version I have done and write about in my blogs): a therapeutic form of fasting where you drink only water for several days, usually under medical supervision.
- Fasting-mimicking diet (FMD): a short period of minimal, specific nutrition that biologically mimics the effect of fasting.
Each of these forms can help the body lower insulin, activate fat burning and reduce inflammation — at its own pace and in a way that suits your situation.
The physiological phases of fasting
During fasting, your body goes through a number of natural phases:
Glycogen phase (0–24 hours): the body uses stored sugars from the liver as an energy source.
Transition to fat burning (24–48 hours): glycogen is depleted, fat burning begins.
Ketosis and autophagy (from 2–3 days): the body converts fats into ketones (a clean fuel for the brain and cells) and starts clearing out old or damaged cells.
Recovery and regeneration (from day 4–5): many people experience a sudden increase in energy, mental clarity and inner peace.
It is normal to feel tired, have headaches or feel slightly dizzy during the first few days — these are transitional symptoms as the body switches from burning sugar to burning fat.
After about day 4-5, this usually stabilises and you will actually have more energy.
Why fasting can help with Long COVID
Long COVID often causes the body to become dysregulated: the immune system remains overactive, metabolism is disrupted and energy metabolism falters.
Fasting can help in such situations by:
Reducing insulin resistance, which restores the flow of energy to the cells.
Calming inflammatory processes, allowing immune cells to function better.
Activating autophagy, which clears away damaged cells.
Calming the nervous system by stabilising blood sugar and stress hormones.
Although research is still ongoing, more and more doctors are seeing fasting as a powerful natural aid in the recovery from chronic fatigue, metabolic complaints and long-term inflammation.
When to be cautious
Prolonged water fasting is not suitable for everyone.
Be cautious if you have POTS, heart palpitations, are taking medication, are underweight or have hormonal imbalances.
Always start with shorter fasting periods (such as 14–16 hours) and listen carefully to your body. If necessary, consult a doctor or specialist therapist.
Interrupt the fast if you feel dizzy, anxious or too exhausted.
Why no flavours, lemon or coffee?
During fasting, you want to allow the nervous system and digestion to completely relax.
When you taste something — even a few drops of lemon, a flavouring or a sip of coffee — it activates the sensory system: your tongue, sense of smell and brain send signals to the stomach and pancreas that “food is on its way”.
This triggers digestive juices and insulin, interrupting the recovery process that takes place in silence.
That is why pure water is the safest choice during a water fast.
With intermittent fasting, black coffee or herbal tea is sometimes allowed, but if you are hypersensitive to stimuli (as with POTS or long COVID), even that can be too stimulating. In that case, it is better to opt for rest and water.
Women and the cycle
For women, it is important to align fasting with the hormonal cycle.
The first day of menstruation is often seen as an ideal time to start a mild fast: the body is then focused on letting go and cleansing.
The follicular phase (days 1–14) is usually the best period for longer or deeper fasting — oestrogen rises, energy is more stable and the body recovers more easily.
Around ovulation and especially in the luteal phase (the week before menstruation), the body actually needs more nutrition, minerals and rest. It is better not to fast too strictly and to eat sufficient protein and healthy fats.
Listening to your cycle also means listening to your natural rhythm — fasting should be supportive, not burdensome.
How to get started if you think ‘I can’t do this’
Start small!
Replace breakfast with a cup of herbal tea and move your first meal a little later in the day. Or take breakfast, eat dinner early and go through the evening with water only.
Slowly build up to 14 or 16 hours without food.
Don’t focus on persevering, but on observing what changes in your body.
With every small step, you train your metabolism, your discipline and your confidence in your ability to recover.
Refeeding: The art and importance of it
After a period of fasting, perhaps the most important part begins: the refeed — the moment when you gradually reintroduce food to the body.
Many people focus their attention on the fasting itself, but forget that the real recovery takes place in the days that follow, when you start fuelling your body again.
During fasting, the body is in a deep recovery mode.
Digestion, enzymes and intestinal activity are slowed down. When you suddenly eat too much — or too much fat, salt or protein — the body can become overstimulated.
The result?
Abdominal pain, nausea, swelling, palpitations or fatigue. Believe me! Even after two weeks of refeeding, eating the wrong foods will cause your body to react violently.
A good refeed is therefore not a “feast”, but a gentle transition back to food.
You give your digestive system time to wake up, produce enzymes and learn to process nutrients again.
If you have fasted for three days, allow yourself three days to fully rebuild.
Start with light, water- and fibre-rich foods such as steamed vegetables, thin soups or soft vegetable dishes.
Then slowly add healthy fats and proteins.
The goal is not to quickly return to “normal” eating, but to prolong the recovery process.
During fasting, the body enters a state of autophagy — a natural cleansing mechanism in which old or damaged cells are broken down and reused. As soon as you start eating protein again, this process slows down.
That’s not a bad thing — it means your body is switching from cleaning up to building up.
That’s why it’s good to make the transition consciously.
A plant-based, whole food refeed (think vegetables, light soups, fruit, some rice or lentils) keeps the body in that restorative, calm state for a while longer.
Only then is it time to add more protein and fat, so that the body can regenerate and repair tissue.
My biggest tip: listen carefully to the signals your body gives you throughout the process!
All right, one more free tip: A great deal of knowledge and experience is shared on forums and groups on Facebook or Reddit. If you need a support group, you may want to check them out. The Longcofit community is also there for you to join.
Inspiring experts to follow
Dr Alan Goldhamer – specialist in medically supervised water fasting
Dr. Jason Fung – nephrologist and author of The Complete Guide to Fasting
Prof. Valter Longo – researcher of the fasting-mimicking diet and cell rejuvenation
Dr. Peter Attia – explains the link between fasting, metabolism and longevity
Dr. Krista Varady – scientist specialising in intermittent fasting