With classic therapeutic fasting, food is avoided for several days. With intermittent fasting, it is sufficient to take regular meal breaks. But is it really good for your weight and metabolism? And what does science say about it?
For many people, the beginning of the year is traditionally associated with good resolutions. Losing weight is one of the most popular goals. And there is no shortage of options, diets abound. But these are often associated with giving up certain foods – which many people cannot keep up with in the long term. Another way of tackling the love handles is intermittent fasting. In contrast to diets, this is not about a change in diet, but only about a time shift of the meal and regular longer meal breaks.
Anna Engler discovered this trend for herself and has already lost 14 kilos. She has been fasting according to the 16: 8 method for a year: for 16 hours she refrains from solid food and only drinks black coffee, tea or water. Eating is allowed in the remaining eight hours. “I don’t even have to go without my favorite foods, pizza and börek,” says the Berliner. Your meal breaks therefore last from dinner to lunch the following day. According to her own words, this rhythm is easy. She never liked breakfast anyway.
No drive, little discipline and too many pounds – those were her problems for a long time. The 32-year-old was significantly overweight, but did not feel like dieting. “I’ve always found them stupid, after all, you can quickly put the weight back on afterwards,” she says. “It seems to be a method that can be incorporated into everyday life relatively easily without causing major distortions,” says Stephan Herzig, referring to intermittent fasting. He heads the “Diabetes and Cancer” institute at the Helmholtz Center in Munich and researches with his colleagues how temporary fasting affects the metabolism. Intermittent fasting has many other positive effects in addition to losing weight. “It ensures, for example, that insulin works better again, it lowers blood pressure, prevents cardiovascular diseases in the long term and also supports cancer therapies,” says Herzig. The scientist and his colleagues are currently working on the question of how fasting can be used for therapeutic purposes and how drugs can be developed that imitate starvation.
Fasting activates the body’s own garbage disposal
But what actually happens when you fast? “Even during periods of starvation, the body must ensure that the organs and especially the brain continue to be supplied with energy,” explains Herzig. When starving, there is a switch from sugar metabolism to fat metabolism. That means, when the carbohydrates are used up, it goes to the fat reserves, the cushions shrink. “If you are hungry for a long time, the protein reserves in the muscles are also attacked,” says the biologist. The breakdown products end up in the liver, which they use to produce sugar in order to supply the brain with it.
“What happens in individual cells depends on the cell type,” says the scientist. But one process is activated in the whole body when starving: the internal garbage disposal, the so-called autophagy. “In the process, defective or damaged molecules are broken down or chopped up into small pieces. It’s a kind of detoxification,” says Herzig.
At the German Institute for Nutritional Research in Potsdam-Rehbrücke, scientists have shown on mice how controlled starvation affects the metabolism: “You can switch back and forth between sugar and fat metabolism much better, the entire fat metabolism improves,” says Annette Schürmann , Head of the Department of Experimental Diabetology. In addition, less toxic intermediate products of lipid metabolism accumulated in the liver. “And the mice react more sensitively to the hormone insulin, which controls sugar. This helps prevent diabetes 2 disease,” said Schürmann. In fat mice that have already developed insulin resistance, this has regressed through fasting. “The metabolism of mice can be compared very well with that of humans, so that these findings can be transferred to humans,” says the scientist.
“There is an incredible amount of very impressive research on animals.” Studies also suggest that fasting protects against dementia, adds Andreas Michalsen, chief physician at Berlin’s Immanuel Hospital. But it is not known whether it also has so many positive effects on humans. “The large, long-term studies on humans are still missing. But the fact that turning the clock does something has been proven,” said the doctor. According to Michalsen, around 1500 fasting people are cared for at the Immanuel Hospital every year. He himself has contact with around 50
0 intermittent fasting per year.
Other studies have also shown that fasting increases memory performance, adds the Munich scientist Herzig. Overall, people are also much more agile in periods of hunger. “The urge to move is increased. You needed that in the Stone Age to survive,” says the researcher. Because at that time food was very scarce and irregular. “People were constantly on the lookout for it. Basically, intermittent fasting reactivates a genetic program, which is hardly used today because of the excess of food. Starvation means that our metabolism goes back to where we used to be,” summarizes Herzig .
Instead of “eat half” the following applies: “eat half the time”
Sometimes starving yourself is exhausting, Anna Engler admits: “I sometimes feel dizzy. But the realization that nothing really bad happens to me when I’m hungry for a few hours was very liberating,” she says. She did not even choose the most difficult variant: “Real” intermittent fasting means going without food for one day and eating one day – and always alternating. Another form is the 5: 2 method. Fasters eat normally for five days a week and only consume around 500 kilocalories on two days. The doctor and entertainer Eckart von Hirschhausen once put the principle of intermittent fasting in a nutshell: “You don’t have to count calories, you have to count hours. Instead of ‘eat half’ the following applies: ‘eat half the time!” “. He also lost ten kilos as a result.
However, not everyone can endure periods of hunger well. Andreas Michalsen observes this again and again. “90 percent think that’s great. Ten percent don’t feel good. I say to these patients: Please don’t do it,” Michalsen said. “I recommend that patients try it out for themselves and find a suitable rhythm,” says the doctor, who himself skips breakfast. According to Stephan Herzig, it would be even better for the metabolism not to eat dinner. “Because the metabolism is linked to the body’s internal clock and the body processes food even better in the morning than in the evening,” says the expert. But for many people this is more difficult to implement. And the change in meal times only makes sense if you can keep it up over the long term.
Studies on long-term effects are lacking
Intermittent fasting has not only advocates: The German Nutrition Society (DGE) does not consider it suitable for regulating weight in the long term. There was a lack of concrete recommendations for food choice, so the reasoning. In addition, there are no studies on the long-term effects of intermittent fasting. Scientists from the German Cancer Research Center and the University Hospital in Heidelberg have now shown in a clinical study with 150 participants that neither euphoric expectations of intermittent fasting nor rejection are justified. “Intermittent fasting has the same strong effects on metabolism and weight loss as a normal weight-loss diet,” says the lead scientist of the study, Tilman Kühn. Two other research groups from Norway and Australia recently achieved similar results.
In Heidelberg, one group fasted according to the 5: 2 principle and consumed a total of 20 percent fewer calories per week. Another group consumed 20 percent fewer calories every day. And a control group ate without a specific diet plan. “Both the interval fasters and the participants from the diet group lost weight. In all participants, the unhealthy abdominal fat and liver fat decreased. In addition, the insulin sensitivity increased again,” reports Kühn.
Whether the results also apply to other fasting methods such as 16: 8 remains to be seen. Another question that preoccupies the scientist is for whom each type of diet is particularly suitable. The participants continued in very different ways after the study: “Some continued to lose weight, others gained weight again. There was a great deal of variation,” said Kühn. “Intermittent fasting may be particularly suitable for working people or retirees. We want to find out,” said the researcher. In the end, however, the most important result is: Regardless of the form of losing weight, it depends on perseverance. “In order to maintain your weight in the long term, you also need a permanent change in diet to a balanced diet according to the recommendations of the DGE,” advises Kühn.
Anna Engler is convinced of her path. She wants to come back to 68 kilos and wear size 38. “There are only six kilos missing,” says the 1.68-meter woman. Long-term perseverance is relatively easy because she only fasts four days a week. From a researcher’s point of view, seven days a week would be ideal. “But longer meal breaks
