An ancient and time-honoured practice, long embraced for spiritual purposes, fasting has in recent years become better known for the health benefits attributed to it. But is fasting actually good for you? What is a 24-hour water fast, what can you drink during those 24 hours without food, and what benefits is it said to offer? Here is how it works, 5 lesser-known benefits, and answers to the most common questions: how to get started, which precautions to take and what we know about its effects on weight.
What is a 24-hour fast?
A 24-hour fast is a water fast, meaning its principle is based on the complete absence of food intake but the freedom to drink, as long as the drinks contain no calories. So during these 24 hours without food, you can drink:
- water, as much as you like;
- herbal teas;
- optionally, a lemon juice diluted in water in the morning;
- a clear vegetable broth with no salt or fat.
It also means avoiding all stimulants, such as tea, coffee or tobacco.
It’s also worth noting that during the fasting period, it is advisable to avoid stressful situations while staying physically active, that is, continuing to stretch and even walk a little.
This form of intermittent fasting , much like sequential fasting or the 5:2 diet, is growing increasingly popular. It is credited with a wide range of benefits. But what exactly are they?
Benefit no. 1 of the 24-hour fast: giving your digestive system a rest
During a 24-hour fast, the digestive organs are given a complete break. The stomach no longer needs to digest any food, since none is consumed. Even more interesting: the pancreas secretes less insulin, the hormone responsible for converting dietary glucose into energy reserves. The same applies to the liver and gallbladder, which are no longer called upon by the digestive process. The feeling of lightness experienced during a 24-hour fast is therefore not only due to the absence of food in your stomach, but also to the absence of digestion itself, a process that, as we know, demands a great deal of energy from the body!
Benefit no. 2: encouraging you to stay well hydrated
A 24-hour fast is a water fast: it encourages you to drink plenty. And we all know that more often than not, we simply don’t drink enough. Yet we cannot survive without water, and beyond that, water plays a key role in keeping the body functioning well. This is one of the real advantages of fasting: it encourages you to stay well hydrated throughout the day. Think of it as a short pause in your usual routine, alongside other everyday habits worth adopting! There’s another reason to drink more: you’re not eating during the fast. Staying well hydrated is therefore all the more welcome throughout those 24 hours.
Benefit no. 3: what is said about oxidative stress
Fasting triggers a paradoxical phenomenon: it causes a slight increase in oxidative stress (an excess of free radicals in the body, which attack cells and in particular DNA), but also a greater resistance to it. In reality, the rise in free radicals is only temporary: the body would respond by ramping up its production of antioxidant enzymes. By inducing mild oxidative stress, a 24-hour fast would therefore prompt the body to adapt. This mechanism has yet to be confirmed for each individual.
Benefit no. 4: a suggested benefit where insulin is concerned
Could a 24-hour fast have a benefit where insulin is concerned? When practised regularly (for example, one day per week, every week), it is said to lead the body to secrete less insulin. Over the course of a full day, the body no longer needs to metabolise any carbohydrates:
- the pancreas secretes less insulin;
- blood sugar levels drop;
- the body draws on its reserves to find energy sources;
- when normal eating resumes, the body would be more sensitive to insulin.
This is a medical matter, however: if you have diabetes or any questions about your blood sugar, ask a doctor for advice before any fast.
Benefit no. 5: reconnecting with the feeling of hunger
What happens when you stop eating? You get hungry — of course! And that’s actually a good thing, because eating is all too often driven by the clock (“it’s time to eat”) rather than by genuine hunger signals. The 24-hour fast has the distinct advantage of helping you reconnect with your body’s physiological hunger cues: a rumbling stomach, a dry mouth, a passing wave of fatigue (low blood sugar), sometimes a headache or a shift in mood. When you return to your normal eating routine, you’re better equipped to recognise when you’re truly hungry and when to stop eating (the much-talked-about satiety), because you’ve become more attuned to your body’s signals.
Common questions about the 24-hour fast
How do you start a 24-hour fast?
Whenever you feel ready — ideally choosing a quiet day with no particular social commitments: no family gatherings, no work, no plans with friends. It’s also advisable to begin your fast after dinner and break it at dinner the following day.
Is fasting for 24 hours dangerous?
It isn’t suitable for everyone, and you need to be in good health. One important note: a 24-hour fast is not recommended for pregnant women or those who are breastfeeding, nor for people with eating disorders or chronic conditions (including diabetes). Seeking medical advice beforehand is always a good idea!
Does this type of fast help with weight loss?
Opinions are divided. A single 24-hour fast, done once in a lifetime, will have virtually no impact on weight. If it becomes a regular habit (for example, once a week), it could potentially have an effect on weight, but this appears to vary a great deal from person to person: it remains uncertain. Fasting is no substitute for a balanced diet, and if you have any questions about your weight, ask a doctor for advice.
What are the side effects of a 24-hour fast?
They can be a little unpleasant: headaches, low energy, as well as effects on mood — including heightened emotionality and irritability — and on concentration (the brain needs glucose to function properly). That said, a 24-hour fast is short-lived, and everything returns to normal as soon as it’s broken.
Frequently asked questions
What is a water fast?
It’s a fast with no food at all, during which you can only have calorie-free drinks. The list of what you can drink, and what’s best avoided, is in the first section of the article, “What is a 24-hour fast?”.
What should you eat after a 24-hour fast?
The article suggests breaking your fast at dinner the following day, then returning to your usual routine while paying attention to your hunger and feeling of fullness. If you’re unsure or have a particular medical condition, ask a doctor or another medical professional for advice.
How long can a person go without food?
This article only covers the 24-hour fast and doesn’t discuss longer periods without food. For any questions on this subject, ask a doctor or another medical professional for advice.
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