Can fasting improve your health?

Whether at home or in treatment centres, more and more people in Switzerland are fasting for prolonged periods or intermittently. In the majority of cases, their goal is to detox, take time for themselves, regain energy, and possibly lose a few kilos. These positive results, praised by several of her friends, convinced Chantal, a sixty-year-old from Neuchâtel, to go on a retreat in the South of France. “We first had a week of preparation at home in Switzerland, a so-called food reduction with a gradual decrease in calorie intake, as well as, according to each person’s preferences, a colon cleaning or a juice-based purge. Then, we went to a place in the wilderness for the week of fasting. There, we mainly drank herbal teas and broths, walked for about two hours a day, had nap times, and attended lectures and discussions on fasting and other topics in the evening.” The novice was amazed at how quickly her body adapted to a diet of less than 250 calories per day. “I suffered from a little fatigue and a great feeling of hunger during the first three days, but after that, I had energy again.” She takes a positive view of the experience, with increased gustatory pleasure. “I savored like never before the potato that was served to us when it was time to resume eating.” She also says she felt great serenity upon returning from her retreat.

Participants in the same retreat resorted to fasting for health reasons, because they suffered from chronic diseases. "It was not their first fast; they were regularly doing cures, including at home, because it relieves ailments related to arthritis problems or muscle diseases that they could not cure with conventional medicine," says the Swiss woman. This type of therapeutic goal is recognised in Germany, where fasting can be prescribed and reimbursed by health insurance, also in cases of hypertension, rheumatism, or type 2 diabetes. Hospitals organise fasts, like the Charité hospital in Berlin or private clinics such as the Buchinger Wilhelmi Clinic, which has received more than half a million people in its cure center, inaugurated in 1953 on the shores of Lake Constance. Unlike non-medicalized retreats or self-care courses at home, a follow-up by health professionals with examinations is organized in this framework before, during, and after fasting.

In Switzerland, fasting is not covered by LAMal. Studies are underway to determine the relevance of the approach. "There is no evidence in the current scientific literature to say that the practice of long fasting meets the needs of all people," explains Sylvie Borloz, a registered dietitian at the CHUV department of endocrinology, diabetology, and metabolism. A long fast, according to the Buchinger method, spans at least four consecutive days, depending on the needs and constitution of the person, with caloric intakes between 70 and 250 kcal per day. 

The dietitian acknowledges that individual observations point to better comfort. “Fasting (several days or intermittent) pushes the organism to tap into its reserves, promoting a self-cleaning system of cells, known as autophagy.” She is more skeptical about the effects of colon cleansing. “We know the importance of flora, and the goal is to cultivate it, to balance it through feeding rather than purging it.” 

Several scientists are currently investigating possible positive effects on organs outside the digestive system, or in the prevention of neurodegenerative diseases, cardiovascular or forms of cancer. “There have been interesting results on animals, but no long-term studies on humans yet.” 

The phenomenon of intermittent fasting

Having found the process of the long fast a bit restrictive, Chantal decided instead to start intermittent fasting. “I decided every day to have dinner, then to have supper, and finally to stop eating until the following noon. I often felt heavy or bloated in the morning after my breakfast, although it was healthy, consisting of muesli, for example. I wanted to regain energy and control my weight. I have been doing this for almost two years, my body has gotten used to it well, I am no longer hungry before 11-11:30 AM now, and I feel healthier, I even manage to work out in the morning.” At the same time, she doesn’t feel as though she is making great sacrifices. “I do not skip the evening meal, which is important for my social life, and I’m giving myself a few cheat meals, for example, if I am on vacation and there is a wonderful breakfast buffet.”

Faced with the recent success of intermittent fasting, to which dozens of books, podcasts, and mobile applications have been devoted for several years, practitioners as well as the research community are analysing its possible positive effect on obesity or diabetes. “Intermittent fasting consists in limiting the period during which food is consumed,” Sylvie Borloz reminds us. This timeframe is usually about ten hours. In practice, this can mean eating in the morning and having your last meal of the day between 4 PM and 6 PM, or postponing the first meal until noon. However, guidelines recommend finishing eating a little earlier in the day, which makes more sense from a metabolic and hormonal point of view.” 

The benefit of intermittent fasting compared to other dietary patterns is that it focuses less on the quantities consumed during meals and more on reducing the frequency of meals and snacks (barring any eating disorders). It can also help to feel hunger better. By reducing the time frame in which one eats, we also potentially limit their caloric intake, and this can lead to slight weight loss in the short term. “However, if it is the desired goal, it can be useful to consult a multidisciplinary team (doctor, dietitian, sports professional, etc.), says Sylvie Borloz. The goal is to determine the most appropriate changes in behaviour to maintain this weight loss over time.”

As with cures lasting several days, the benefits of intermittent fasting for those who are sick are also difficult to assess. Establishing a period where one does not eat would prevent glycemic and insulin peaks. “For diseases such as diabetes, studies show that practice allows people who suffer from it to regulate their blood sugar better and improve their insulin resistance.” There could also be a positive effect on cardiovascular diseases. “However, it is difficult to dissociate this beneficial impact from other lifestyle factors such as physical activity or the quality of food consumed, for example.”

No generalised recommendation

In healthy people, long fasting does not seem to present harmful effects, according to a study conducted by the CHU of Saint-Etienne in France with the Buchinger Wilhelmi clinic last year. Participants in a 12-day fast were examined with an MRI scan just after fasting, after two months, and four months later. They preserve all their muscles, and their organs (heart, brain, etc.) adapt to the metabolic change that occurred during the cure. However, all fasting practices, both long and intermittent, are contraindicated for people suffering from eating disorders and emotional management problems. "Depriving oneself of food implies restrictions and can therefore generate food cravings," reminds the dietitian from CHUV. It is also not recommended for children and elderly people, whose appetite is lower and for whom three meals a day, as well as snacks, are important. 

One of the limits of a widespread recommendation of long fasting also concerns its feasibility. “This is a rather cumbersome practice that requires drastically lowering calories for a week or more, or even going to a clinic. This requires financial means and enough time.”

A healthy lifestyle

Long or intermittent fasting has not yet been shown to have better results than current dietary recommendations. “In the studies on this topic, intermittent fasting periods usually only last a few months and involve small groups of participants, because it is complicated to recruit populations who follow this dietary pattern for longer. Therefore, there is missing data on intermittent fasting in the long term, warns the dietitian. Conversely, recommendations such as the consumption of foods rich in fiber, plant-based protein, and the reduction of certain animal products and sugary or alcoholic drinks have clearly shown positive results for all types of populations. This makes it a more interesting habit than fasting practices for the majority of people.”

The dietician also fears abuses, as in the case of other restrictive diets. “This should not be a way to compensate for excesses, as can happen in some diets, leading to the yoyo effect and ultimately a problematic relationship with food. If it is a week in the year without any change in lifestyle habits or intermittent fasting that is not carried out consistently, there can be no positive effects in the long term. Consulting a doctor is recommended before starting a fast.