How Good is Fasting?

Those who fast lose weight, live healthier and find their spiritual center. Is that correct or not? The scientific facts.

What is fasting?

Fasting is not a crash diet where you stop eating overnight – even if it seems so at first glance. The medical association for therapeutic fasting and nutrition defines fasting in its guideline on fasting therapy as “voluntarily abstaining from solid food and stimulants for a limited period of time”. On so-called relief days, on which only light fare is on the menu, you feel your way towards giving up.

It is important that fasting people drink a lot : 2.5 liters per day, of course sugar-free. However, up to 500 calories can be consumed daily via vegetable broth or fruit and vegetable juices. Despite this low energy intake (about 2000 calories per day is normal), the body should not be spared, but exercised regularly. Towards the end of the cure, it’s time to gradually get back to normal food – so not two cups of vegetable broth today and burgers and fries tomorrow.

Different approaches and spirituality

There are different methods of fasting , one of the best known is Buchinger’s. Depending on the state of health, the concrete forms differ and range from therapeutic to preventive fasting to fasting for healthy people.

In addition to the health side, fasting also has a spiritual side: a culture of fasting can be found in all major world religions. The goals behind it are similar – to get closer to one’s own faith through abstinence.

What happens in the body when we fast?

If the body suddenly only has 500 calories of energy available instead of the daily 2000, it has to adapt. The metabolism changes, switches to economy mode and draws on its energy stores : glycogen, fat and protein.

First it goes to the stored sugar, which is found as glycogen in the liver. However, these reserves are empty after 24 hours at the latest. Next, protein is broken down: Proteins, which are found in the intestines or muscles, for example, provide energy. But only for a limited time – if the body loses too much of its own protein, it becomes life-threatening. By the way: So that the muscles don’t suffer during fasting, there are usually a few carbohydrates in professional fasting cures, for example honey or fruit juices.

Fat is only broken down after four days

The most important source of energy, however, is in the hips, legs or buttocks. The adipose tissue of a healthy man weighing 70 kilograms would theoretically be enough to provide him with enough energy to survive for 70 days without food . After about four days of fasting, the body begins to digest fat. However, this actually positive development (keyword: losing weight!) has an unpleasant side effect: you start to stink. The body disposes of acetoacetic acid, a so-called ketone body, which is produced when fat is burned, through sweat and the air we breathe.

Is Fasting Harmful?

From an evolutionary point of view, the constant supply of food as we know it today is rather unusual. If you think of hunters and gatherers in the Stone Age or even of self-sufficient farmers a few hundred years back, it becomes clear: There have always been phases of hunger. And the human body had to find a way to deal with it.

Risk-free despite possible side effects

Since today’s fasting is not a long-term zero diet, the change in diet does not affect you that much. Fasting is therefore generally considered to be well tolerated and risk -free for healthy adults . Of course there can be side effects , for example: circulatory problems, slight hypoglycaemia, disturbances in the electrolyte balance, headaches, migraine attacks, lumbago, muscle cramps, blurred vision (temporary), water retention and sleep changes.

Pregnant women should not fast

Some people are explicitly advised against fasting therapy, for example with certain pre-existing conditions. These include: Pregnant and breastfeeding women, people with eating disorders, dementia, type 1 diabetes or impaired liver or kidney function.

Does fasting detoxify the body?

“Detox” and “purification” are two words that are often used in connection with fasting. And at least “slag” isn’t a medical term. It is often used because it symbolizes substances that are supposed to leave the body through the fasting metabolism. Lay people think of these substances as bad waste, similar to the slag that is a by-product of the metal industry.

“Detoxification” unscientific

The Medical Society for Therapeutic Fasting and Nutrition criticizes that the non-scientific term “detoxification” is often used by opponents of fasting to question the effectiveness of fasting therapy in general. In doing so, they could use the correct medical term to specify which substances leave the body.

However, it has not been scientifically proven whether toxins, such as gout-triggering urate crystals, really disappear from the system during fasting . Organs such as the liver or kidneys are normally responsible for internal detoxification. When fasting according to Buchinger, their activity should therefore be stimulated – in the case of the liver with hot compresses and in the case of the kidneys with the large amount of liquid.

Does Fasting Have Long-Term Benefits?

As so often in naturopathy, there are two very different camps when it comes to fasting. On one side are the supporters, who conclude on the health benefits of fasting from smaller research, clinical and personal experience. On the other hand, there are critics who complain about the lack of solid scientific evidence and question the effectiveness of fasting. The truth probably lies somewhere in the middle.

Studies insufficient

The fact is: There are no large clinical studies in which a representative number of people have fasted regularly for years and compared them with a non-fasting control group. However, such experiments would be important and necessary in order to clearly prove the effect of fasting cures.

On the other hand, there are studies on a smaller scale, for example over three months. They provide evidence that speaks for positive effects of fasting, both for healthy and sick people. Rheumatism patients in particular can benefit: symptoms improve, inflammation parameters decrease. Data from some observational studies also suggest that fasting helps with chronic musculoskeletal pain.

Blood pressure drops

Further studies indicate a reduction in blood pressure. Although this rises again after the end of the fast, it does not reach the initial values ​​– even in the longer term. Doctors attribute this primarily to weight loss, but also to the change in diet . Because fasting can help overweight people lose weight , above all, because it is a good starting point for a change in eating habits.

Fountain of youth fasting cure? There was evidence in animal studies that fasting has an anti-aging effect and slows down cell aging. However, it is unclear to what extent this can be transferred to humans.

Recent smaller studies also indicate that fasting alongside chemotherapy can have positive effects for cancer patients: the chemo would be better tolerated. Cell-level experiments also showed that fasting could be bad for cancer cells. However, there is still too little scientific evidence for both aspects.

What fasting methods are there?

There are different methods of fasting. One of the best known is the therapeutic fasting method according to Otto Buchinger , a German doctor. This form of fasting often takes place under medical supervision, sometimes even as part of a hospital stay. People don’t eat, but drink more: at least 2.5 liters of calorie-free liquid a day, sometimes with vegetable broth, fruit or vegetable juices. The triad of body, mind and soul is also important in the Buchinger method. In addition to the medical aspects and mutual psychosocial motivation, for example in group sessions, a spiritual dimension should also be taken into account.

A related method from naturopathy is the FX Mayr therapy , a three-stage “intestinal rehabilitation cure”. You keep a tea-water or a milk-bread diet. FX Mayr focuses heavily on gastrointestinal disorders.

The so-called Schroth cure focuses on carbohydrates. Fasting people are only allowed to eat vegetarian food and alternate dry and drinking days. There are also various elimination processes.
A variant of Buchinger’s therapeutic fasting is the whey cure . The liquid food is enriched with proteins, for example with whey. Whey is a by-product of cheese making.

Different approaches to intermittent fasting

In addition to these traditional fasting methods, so-called interval fasting can also be carried out, which is also known under the term “intermittent fasting”. There are many different variants here. Depending on the model, fasting people do without solid food for 16 hours to two days. With 16:8 fasting, for example, you can eat eight hours a day, but not the remaining 16. In addition, you can fast every other day or, in the five-to-two model, two freely selectable days a week. Usually, a maximum of a quarter of the calories actually required is eaten on the fasting days – similar to Buchinger fasting. There are no dietary rules on the fast-free days.

How long should you fast?

Christians traditionally fast for 40 days, Muslims for 29 to 30 days during Ramadan. Fasting cures for health reasons have nothing to do with this religious fasting . That is why they also differ significantly in their duration: the individual state of health and the chosen fasting method are decisive for the length.

Intermittent fasting such as 16:8, in which you fast for 16 hours and eat eight, can probably also be integrated into everyday life in the longer term . On the other hand, more radical fasting diets, in which you only consume a few calories, are intended for a limited time. With Buchinger therapeutic fasting, the Medical Society for Therapeutic Fasting and Nutrition recommends a minimum of eight to ten days of fasting plus a day of rest beforehand and three recovery days afterwards. Shorter periods of fasting can be useful for people who are underweight, but also longer periods for some other indications. You should not fast for more than six weeks. Healthy people can do a so-called fasting week: one day of relief, five days of fasting, two days of recovery.

What is the fasting high?

Fasting often makes you feel unwell at first: there is nothing to eat, at some point you will inevitably be hungry. However, once the body has gotten used to the condition and the metabolism has adjusted, the mood rises. Fasting people report feelings of happiness, good mood and the so-called ” fasting high” .

For the scientific explanation behind it, a look into the brain is necessary. Even with short-term food deprivation, the brain begins to ramp up serotonin production. Serotonin is also commonly known as the happiness hormone. If the fasting period lasts longer than a few days, there is a second effect – the hormone remains in the blood longer and can unfold its mood-enhancing effect there.

Experimental research has shown that, in addition to serotonin, endogenous opioids, i.e. painkillers, and endocannabinoids are available in larger numbers in the brain as a result of fasting. Endocannabinoids are cannabis-like substances that are produced by the body itself. Due to the analgesic and cheering effect of the substances, there are considerations of using fasting in the therapy of patients with chronic pain . In order for this to have a scientifically sound basis, however, more studies with larger numbers of participants must be carried out.

By the way: People with eating disorders or mental problems are sometimes advised against fasting because of the psychological effects. Anyone who only feels good and happy by not eating can easily slip into a kind of dependency.