Fasting and Health: Is It Really Good for You?

Voluntary fasting has moved well beyond its ancient and religious roots to become a modern wellness fixation, embraced as much for what it seems to promise psychologically as for any physiological effect. For some, it offers a sense of control that feels almost restorative in itself: eating is no longer a simple instinctive act, but something disciplined, even spiritual. That helps explain the strength of its appeal. Yet the science remains far less certain than the confidence surrounding it, particularly when it comes to immunity, inflammation and the broader claims often made in its name.

In short: fasting and health

Fasting and health belong in the same conversation only when benefits, risks, medical context and personal suitability are all kept in view.

Use this article as a practical map: keep what helps attention become steadier, question anything that sounds absolute, and connect the idea back to repeatable daily practice.

There is also something deeply revealing in the way fasting is discussed today. It is rarely presented merely as a dietary pattern; more often, it is wrapped in the language of purification, reset, clarity and self-mastery. That vocabulary is not accidental. It speaks to a culture that often feels overfed yet undernourished, overstimulated yet oddly depleted. In that atmosphere, fasting can seem less like deprivation and more like relief. The difficulty, of course, is that emotional resonance is not the same thing as medical proof.

Why Fasting Appeals and Where the Health Risks Begin

Why fasting feels so compelling

Unlike animals, which fast through necessity when food is scarce, people often choose fasting deliberately. That choice helps explain why it has become such a powerful social trend. For some, it promises a reset for the body; for others, it offers a sense of discipline, clarity or even elevation. Yet the science remains far less settled than the confidence of many online claims would suggest, especially when it comes to the immune system and inflammatory disease.

As Bruno Falissard, professor at the Faculty of Medicine at Paris-Sud University, points out, fasting can create the feeling of regaining control: eating is no longer experienced as something purely instinctive, but as an act with a spiritual dimension, closer in spirit to practices such as yoga, where one seeks to master the body and the breath — and, in this case, food itself.

That sense of regained control should not be dismissed too quickly. For many people, food is tied up with habit, comfort, stress, reward and guilt. A fast can therefore feel psychologically clean in a way ordinary healthy eating often does not. It creates a boundary. It simplifies decisions. It can even produce a temporary sense of sharpness or moral clarity that people understandably find persuasive. But what feels clarifying in the moment is not always a reliable guide to what is beneficial over time.

There is also a social dimension to its appeal. Fasting carries a certain prestige in wellness culture because it appears demanding. It suggests discipline, resilience and seriousness. In a world crowded with convenience and excess, restraint can look almost noble. Yet that image can be misleading. Some people are drawn not by health at all, but by the seductive idea of proving something to themselves. When that happens, fasting can quietly shift from a considered practice into a test of will, and that is often where judgement begins to fray.

That appeal is understandable, but it can also blur judgement. Dr Bruno Raynard, head of the Dietetics and Nutrition Unit at Gustave Roussy, reminds us that fasting does two things at once: it removes nutrient intake — proteins, carbohydrates, fats, vitamins, trace elements and therefore calories — while also interrupting certain harmful cellular processes, including some involved in inflammation. This is precisely why the subject is so difficult to reduce to slogans. The problem is that many people begin fasting on the strength of unfounded promises and dubious diet marketing, without considering whether their health might make the practice risky.

In people with diabetes, existing anaemia or low blood pressure, for instance, an unsupervised fast can worsen an already fragile situation.

It is worth lingering on that point, because the body does not experience fasting as an abstract wellness concept. It experiences it as altered fuel availability, hormonal change, fluid shifts and metabolic stress. For a healthy person under sensible conditions, that may be manageable. For someone already vulnerable, it may not be. The same practice that one person describes as invigorating may leave another dizzy, depleted, anxious or unwell. This is one reason fasting advice becomes so muddled online: personal testimony is vivid, but it is not universally transferable.

• Fasting may feel psychologically empowering.
• Scientific evidence is still incomplete in several key areas.
• Underlying health conditions can make self-directed fasting unsafe.

Where caution matters more than enthusiasm

The same need for perspective applies to some of the boldest claims made in favour of fasting. Assertions that it can replace cancer care are not supported by current scientific evidence, even if some contemporary oncology research — particularly around chemotherapy — is encouraging. Nor should religious traditions be used as a shortcut to justify modern fasting remedies: in many cases, those traditions involve only partial calorie restriction for less than 24 hours, which is very different from prolonged therapeutic fasting. In practice, fasting calls for precautions before, during and after the process, starting with something basic but essential: regular hydration, with around 1.5 litres of water a day on average.

Hydration sounds almost too obvious to mention, yet it is often treated casually by people who romanticise fasting as a pure act of abstinence. In reality, the body tolerates restriction far less well when fluid intake is neglected. Headaches, fatigue, light-headedness and poor concentration may be interpreted as signs of “detox” or adaptation, when they are sometimes simply signs that the body is struggling. That is one of the recurring problems with fasting culture: discomfort is too easily rebranded as progress.

Preparation matters as much as the fast itself. Someone who moves into a fasting period after days of erratic eating, poor sleep, high stress and too much caffeine is not beginning from a neutral baseline. Equally, the period after a fast deserves more respect than it usually receives. Returning abruptly to heavy meals, alcohol or highly processed food can leave people feeling distinctly worse, not better. The beginning, middle and end of a fast all matter; treating only the fasting window as important is a common mistake.

Even so, the subject remains open rather than closed. Canadian research has raised the possibility that intermittent fasting may help in the management of type 2 diabetes, and that helps explain why it is so often presented as the most sensible form of fasting. There are also studies suggesting that a three-day fast could renew the immune system more broadly, an idea reinforced by work from a team at the University of Southern California. These findings are intriguing, but they are not a licence to improvise. Fasting may hold real promise, yet it still demands medical judgement, especially when the body is already dealing with illness, medication or metabolic imbalance.

That is the more mature way to read the evidence: with interest, but without haste. Early findings can be valuable. They can open doors, challenge assumptions and point medicine towards useful therapeutic tools. But they do not justify turning a developing area of research into a mass-market certainty. The gap between a promising study and a safe public recommendation is often much wider than wellness culture likes to admit.

• Claims of cancer remedies remain unproven.
• Hydration is a non-negotiable part of any fast.
• Intermittent fasting is being studied for type 2 diabetes.
• Promising results do not remove the need for supervision.

What Intermittent Fasting May Offer, and Why It Still Demands Care

Promising findings, but not a licence to improvise

Some of the most encouraging claims around fasting come from research on intermittent or partial fasting, rather than from extreme unsupervised restriction. American researchers, in findings published in CELL after a pilot study in men, suggested that fasting for five days a month could benefit the heart by lowering cardiovascular risk. More broadly, many researchers now believe fasting may help reduce some of the so-called modern illnesses linked to poor diet and ultra-processed food. It has also been discussed as a possible support in certain recurring psychiatric disorders, though only under proper supervision.

In oncology too, the work presented at the Norris Cancer Hospital in Los Angeles by Professor Valter Longo has drawn attention, particularly in relation to chemotherapy and the potential value of partial fasting.

What makes intermittent fasting so attractive is that it appears to offer some of the possible benefits of fasting without demanding the severity of a prolonged fast. For many people, that makes it feel more realistic and less intimidating. It can be folded into ordinary life more easily, whether through time-restricted eating or occasional shorter fasts. That practicality partly explains its popularity. It feels less like stepping outside life and more like adjusting its rhythm.

Even so, “more practical” should not be confused with “automatically appropriate”. Intermittent fasting can still affect blood sugar, mood, energy, sleep and concentration. Some people adapt well; others become irritable, preoccupied with food or prone to overeating once the eating window opens. In those cases, the method may be technically fashionable but personally unhelpful. A protocol that looks elegant on paper can become quite clumsy in lived experience.

That said, none of this means people should start experimenting on themselves. Fasting may have real therapeutic promise, but it is not a harmless wellness challenge. The older practice of fasting is often associated with a wide range of possible benefits, from cognitive function and immune defence to skin regeneration, weight loss, diabetes management and even depression. Yet these possibilities only make sense when approached with caution. In practice, this kind of experience calls for medical guidance, ideally from a health professional working in a specialised setting, especially when the aim goes beyond simple dietary adjustment.

There is also a difference between using fasting as a structured therapeutic tool and using it as a vague answer to feeling unwell. The first belongs, if anywhere, in a careful clinical or professionally guided context. The second is where trouble often begins. People who are tired, inflamed, emotionally strained or unhappy with their weight are often especially vulnerable to grand promises. Fasting can then become a vessel for hope that is far larger than the evidence can carry.

• cardiovascular health
• metabolic disorders linked to poor diet
• supportive use in some psychiatric conditions
• partial fasting in oncology research

One body is not another

The wisest principle here may be the one John J. Medina highlights in his 12 Rules for the Brain: uniqueness. What suits one person may be ineffective, or even dangerous, for another. The old Chinese saying captures it neatly: “10,000 monks, 10,000 religions.” Even intermittent fasting, often presented as the gentlest option because it involves shorter but regular fasts, should not be started blindly. A health check matters, particularly if you take medication. The right approach is not to copy a trend, but to find a method that fits your own health profile, in agreement with your GP or treating doctor.

This principle of uniqueness is not a polite disclaimer; it is central to the whole question. Age, sex, medical history, stress load, sleep quality, medication, activity level and relationship with food all shape how fasting is experienced. A person with stable energy, good metabolic health and a calm eating pattern may respond very differently from someone who is already exhausted, hormonally vulnerable or prone to restrictive habits. To ignore those differences is to mistake a body for a theory.

It is also why blanket advice can be so unhelpful. The internet tends to reward certainty, and fasting is often sold in neat formulas: skip breakfast, compress the eating window, push through the hunger, trust the process. Real bodies are rarely that obedient. Some people feel better eating earlier in the day; others struggle if they delay food too long. Some tolerate short fasts but not repeated ones. Some discover that what they needed was not fasting at all, but steadier meals, less processed food and a more settled nervous system.

For that reason, it generally makes more sense to begin with intermittent fasting before considering anything longer than 72 hours, or more demanding approaches such as the Warrior Diet popularised by nutrition specialist Ori Hofmekler. A former member of the Israeli special forces, he studied how the human body reacts to extreme stress in survival conditions and linked those observations to the habits of ancient warriors, advocating food that is barely cooked and unprocessed. Even so, before embracing any fasting protocol, the more sensible first step is often much simpler: eat well.

At a time when food culture swings between fermented food trends showcased at SIAL Paris and the excesses of freeze-dried sweets, gold-flake chewing gum, collagen tea and relentless junk food, better-quality eating remains the soundest foundation. Fasting may well have a place in preventing or easing some of the ailments of modern life, and medicine would benefit from taking that possibility seriously. But it should never distract from the basics, especially when poor diet and emotional distress are already weighing heavily on younger generations.

That final point deserves emphasis. There is something slightly perverse in searching for salvation through fasting while ignoring the daily damage done by ultra-processed food, erratic eating, chronic stress and poor sleep. For many people, the most transformative step is not a dramatic fast but a quieter return to decent nourishment: real food, regular meals, fewer chemical novelties, less nutritional theatre. Fasting may sometimes build on that foundation. It cannot replace it.

And perhaps that is the most honest conclusion of all: fasting is at its most interesting when it is treated neither as a fad nor as a faith. It asks for discernment. It asks for humility. Above all, it asks us to remember that health is rarely restored by extremes alone, however elegant those extremes may look when packaged for modern life.

The Mental Waves Fasting Discernment Framework

The Mental Waves frame for fasting is not enthusiasm or rejection; it is discernment. Fasting changes the body. That means the first question is not whether the practice is fashionable, but whether it is appropriate for this person, this body and this moment.

• Clarify the goal: weight, metabolic health, spiritual discipline and curiosity are different motives.
• Check vulnerability: medication, blood sugar, pregnancy, eating history and illness change the risk profile.
• Prefer the foundation first: real food, hydration, sleep and stress regulation are not optional basics.
• Use supervision when stakes are high: illness, long fasts and therapeutic aims call for qualified guidance.

The Mental Waves Discernment Before Restriction Framework

The Mental Waves frame is to separate conscious discipline from pressure, trend and self-punishment. A fasting practice should never be used to override basic body signals or medical common sense.

Before changing food intake, clarify the reason, the duration, the support available and the warning signs that would make stopping the wiser choice.

If fasting attracts you because your mind feels overloaded or out of control, start instead with the free Mental Reset session and make decisions from a steadier state.

Editorial note from Mental Waves

This article is educational and does not recommend fasting for everyone. Pregnancy, eating disorders, diabetes, chronic illness, medication use or frailty require professional medical guidance before any fasting practice.

Conclusion

Fasting sits in an awkward but honest place: it can be both meaningful and medically interesting, without becoming a miracle solution. Part of its appeal is clearly physiological, but part of it is also psychological and even spiritual — the sense of regaining control in a culture shaped by excess, impulse and ultra-processed food. That helps explain its popularity. Still, popularity is not proof. The research remains incomplete, some findings are promising rather than definitive, and the gap between supervised practice and improvised restriction is where the real risks begin.

It is also worth resisting the temptation to force a simple verdict. People often want fasting to be either vindicated or dismissed, but the truth is less tidy. In some contexts it may prove useful, even genuinely valuable. In others it may be unnecessary, poorly tolerated or plainly unsafe. That ambiguity is not a weakness in the discussion; it is a sign that the subject deserves seriousness rather than slogans.

What emerges, then, is not a simple verdict of “good” or “bad”, but a call for proportion. Intermittent fasting may suit some people better than longer fasts, and certain therapeutic avenues deserve serious medical attention, particularly where inflammation, metabolism or treatment support are concerned. But none of that cancels a basic truth: one body is not another, and fasting can worsen fragile health when it is treated casually or sold as a universal answer. In most cases, the wiser starting point is less dramatic — eat better, know your own health, and seek proper guidance before testing your limits.

Used well, fasting may have a place; used blindly, it becomes just another illusion dressed up as discipline.