Researchers do not detect the side effects of heavy interval fasting 2

Researchers do not detect the side effects of heavy interval fasting

Of all the methods that promise a longer and healthier life, one is particularly promising. This means: eat half! But because only a few manage to do this permanently, scientists (and those who want to lose weight) are looking for other methods. One of them is Intervall fast, so it doesn't eat anything for a while. However, this is always considered critically, as there is only a handful of data on the long-term consequences.

Now scientists from the University of Graz have set their subjects for study at a strictly interval diet. They studied the effects over a period of four and six months. Cell metabolism now reports that participants under such a diet consumed significantly less calories and lost weight. It also brings health benefits. No side effects appeared.


Researchers around Slaven Stekovic from the University of Graz divided 60 healthy normal-weight subjects into two groups for their study. One half was allowed to eat as much as they wanted, the other 30 participants had to follow a strict diet for four weeks. They alternately had to fast for 36 hours – one day and two nights – after which they could eat their normal meal for twelve hours.

To make sure they did not eat during Lent, the researchers monitored blood sugar levels. To evaluate the safety of the method, the researchers also studied another 30 individuals who ate such a rigorous plan for at least six months.

One third less calories

It turned out that during the twelve hours they were allowed to eat, participants recovered some of the calories they lost during fasting, but not all. On average, fasting subjects consumed 37 percent less calories during the four-week trial period and lost 3.5 pounds of body weight.

In addition, blood tests have found different values ​​that link researchers to improved cardiovascular health and increased longevity, such as lower cholesterol levels and reduced abdominal fat. It is just abdominal fat, studies have shown related to the risk of cardiovascular disease.

Other research suggests that such a strong reduction in calories may result in a decrease in bone density or a weakening of the immune system. However, in the study in Graz, there were no side effects among the subjects after six months.

The researchers conclude that the method is safe (at least for this period) and speculate that alternating fasting even has the potential to become a standard in the clinic, such as when overweight patients should lose weight. It is also proposed as a preventative health measure to prevent cardiovascular disease.

The big advantage over traditional calorie reduction is that you don't have to count calories, but you can't afford to eat anything on certain days.

Criticism of study design

Jürgen König is rather skeptical: "Energy reductions should have been expected to have some positive health effects," says the head of the nutrition department at the University of Vienna. However, whether these effects were created by alternative fasting cannot be said based on the study design.

For example, there was no control group in the study that achieved similar calorie reduction as fasting participants through continuous (not intermittent) fasting. Only then could it really be stated whether the method of interval fattening and not calorie reduction would have effects in itself.
Stefan Kabisch, a doctor at the German Institute for Human Nutrition (DIfE) in Potsdam-Rehbrücke, also cites this criticism. The fact that calorie reduction has positive effects has been known for decades. He sharply criticizes the methodology of the study, even confirming that "there are no new useful findings on interstate fasting in humans."

Intermediate fasting can make metabolism more flexible

Annette Schürmann, head of DIFE's Department of Experimental Diabetes, doesn't take it so critically. Although it cannot be deduced from the data that the effects found were caused by the intervalallfast and not in principle reduced calorie intake. "The results of animal testing, however, suggest that fasting intervals, pauses in addition to the known effects of reduced calorie intake, could also have a positive effect," said Tagesspiegel's Schürmann.

For example, compounds (ketone bodies) thought to have a beneficial effect on the cardiovascular system would be formed in lipid metabolism. In addition, the body can better transition from the break from carbohydrate metabolism to fat, which leads to burning of belly fat. Higher insulin sensitivity observed with fasting intervals may also protect against diabetes.

Most of the data comes from animal experiments because human studies – as is often the case in nutrition research – are very time consuming and difficult to conduct. "In this regard, the merits of the Graz researchers have shown the safety of this strict type of interval post," says Schürmann.

"Thinking About What You Become"

More studies should now follow, for example, to check whether alternating fasting is suitable for the treatment of overweight patients. A 2017 American study found that this method of weight loss is difficult for patients to sustain in the medium term. Patients sometimes report severe hunger even after weeks of fasting.
Schürmann advises that no one imitate such a strict interval post as in the study. You should definitely discuss this with your family doctor first. You can try an interval fasting of 16: 8 (do not eat 16 hours a day) or 5: 2 (eat normally for five days but not more than 600 calories for two days). However, it is not recommended for children and adolescents without weight and pregnancy problems.

It is always important to think about why to opt for interval fasting. "If you really want to lose weight, you can't even eat fast food during the time you're allowed to eat," Schürmann says. Because if you go back to your normal calorie count, nothing is gained. The researcher says, "Weight loss is still the biggest factor in losing weight." Whether interval fasting helps is different from person to person. (with smc)