“In 2016, with my first book where I encouraged fasting at home, without medical supervision, I made a huge mistake. Many blamed me for it, a woman even died of it”. By calling Professor Valter Longo, we did not expect such a confession. The Italian-American scientist is considered one of the popes of fasting, and those who promote this practice always end up citing his work on the effects of dietary restriction on tumors or longevity. But the researcher continues his momentum: “Proposing this type of intervention without a protocol validated by science, just because we believe in it, is the best way to have disasters, a bit like with your Pr Raoult and its hydroxychloroquine!”.
Disasters, indeed, there have been. According to Miviludes (Interministerial mission of vigilance and fight against sectarian aberrations), at least three cancer patients have died in recent years after having deprived themselves of food on the advice of naturopaths. In its different forms (short, complete, long, partial, intermittent, etc.), fasting has never been so popular. Structures offering “fasting and hiking” courses are multiplying. There are countless books and laudatory articles – as recently these reports in She or in One of Mthe magazine of World. On the Internet, dedicated applications and hashtags with thousands of views also show growing interest. To listen to the most enthusiastic, it would be almost a panacea that would offer well-being, detoxification, weight loss, and prevent (or even cure!) cardiovascular diseases, diabetes, cancers, inflammatory pathologies and even neurodegenerative conditions…
“The best sign that it’s good for our customers is that they come back,” says Sandrine Bervas. According to the president of the French Fasting and Hiking Federationit all started with a documentary byart of 2012, “Fasting, a new therapy?”. Regularly rebroadcast (again this Wednesday, February 1 on LCP), it “boosts registrations each time”, she rejoices. Among other things, we discover the Buchinger clinic in Germany, a haven of luxury where wealthy customers pay dearly to swallow 300 calories a day in the form of juices and broths and to practice a little physical activity. “Its managers have carried out a lot of research, and many French centers are inspired by it”, underlines Sandrine Bervas.
This work shows that fasters do not suffer from hunger, that they “feel better”, and that parameters such as weight, cholesterol, blood sugar or blood pressure improve. However, these are observational studies with a low level of evidence. The absence of feelings of hunger and the well-being felt are not surprising: “When you fast, the body draws on its glucose reserves, then it diverts the amino acids from the muscles to manufacture sugar, which makes melt lean mass.To slow down this negative effect, after two to three days it will use fat to make ketone bodies, an energy substrate usable by the brain, which puts you in a state of euphoria and cuts the feeling of hunger”, explains Professor Jean-Michel Lecerf, head of the nutrition and physical activity department of the Institut Pasteur de Lille. “Postprandial” inflammation (linked to digestion) disappears, as do the symptoms of irritable bowel (bloating, gas, etc.) for the 15% of the population who suffer from it. “But they come back as soon as we eat again,” warns Professor Lecerf.
The improvement in metabolic markers also leaves nutritionists unmoved. “It’s expected when you don’t eat. What’s next? Diabetes or cardiovascular disease sets in over years. Is there evidence that a transient drop in sugar or cholesterol levels reduces the risk? No”, says Professor David Jacobi, of the Thorax Institute of the Nantes University Hospital. Even weight loss does not seem sustainable: “Fasting is the worst method of losing weight. As after any diet, you regain the pounds lost, but being, in proportion, more fat because you have lost muscle”, continues Professor Lecerf.
In Germany, doctors supervise the cures. Not in France, with rare exceptions – a small group of convinced GPs created the Medical Academy of Fasting, and as such participates in FFJR courses. Provided it does not exceed a week, fasting is generally well tolerated in healthy people. However, it is not without risk. The enemas that often precede it can have “serious consequences, such as perforation, infection, or a change in the intestinal flora”, notes Miviludes. Above all, fasting courses place people in a state conducive to being controlled: “Between euphoria, fatigue, group dynamics and the authority of the supervisor reinforced by the well-being felt, all the ingredients are together, as long as the person is ill-intentioned”, assures Dr Marion Lagneau, member of the office of the collective No FakeMed.
The concept of “detoxification” or the idea of ”boosting your immunity”, often put forward, has no scientific basis. What about the potential “therapeutic” effects of these short periods of restriction? In 2014, Inserm has compiled the available studies, all pathologies combined, without finding conclusive data. Since then, many other studies have been carried out, but they are not, at this stage, much more convincing. In the case of joint diseases, for example, the French Society of Rheumatology does not recommend fasting given the low level of evidence of the published works. Against cancer, the experts of NACRe network (Nutrition, Physical Activity, Cancer Research Network) also explored scientific publications in 2017. Without finding anything more. “The latest studies do not change our conclusions: there is no proof of effectiveness in prevention, and it remains contraindicated in patients”, summarizes Bernard Srour, the coordinator of this structure.
The question had aroused great interest after the first work of Valter Longo: he showed, in animals suffering from cancer, that chemotherapy was more effective and better tolerated in rodents subjected to fasting. “We must remain open, because these results were interesting. But for the moment, they have not been validated on humans”, recalls Dr. Bruno Raynard, nutritionist at the Gustave-Roussy cancer treatment center. This specialist therefore calls for the greatest caution: “We know that patients with serious illnesses do not react to food deprivation in the same way as a healthy person. Inflammation modifies the metabolic response and pushes the body to eat more muscle mass, which is very important to limit complications and the harmful effects of treatments”.
Valter Longo is continuing his research. on cancer, but also on longevity: after proving in different species that calorie restriction prolongs life, he seeks to obtain similar results in humans. He has developed a program of imitation fasting (800 calories per day over 5 days) based on food and food supplements, to be followed at home. The researcher has just launched a clinical trial to validate the effect of repeated cures once a month for three months, in combination or not with a diet similar to the Mediterranean diet, compared to a control group: “We hope to show an improvement in markers of health and aging”. But here again, even if the effects are positive, the question of the persistence of the effect will remain.
Intermittent fasting – every other day, or two days a week – is also well researched, although so far evidence of benefit is also lacking. “On weight, for example, the results are similar to those of a classic calorie restriction diet”, notes Professor Lecerf. At this point, daily fasting seems the most promising. It consists of extending the time slot during which we abstain from eating, and would be easier to maintain over time. “Early studies in humans show effects on metabolic parameters, which also remain to be confirmed,” says Professor Jacobi. One thing is certain: so far, none of these tracks has done better over time than the classic recommendations – physical activity, sleep, varied diet without excess. Enjoy your lunch !
