Starve to health

Six months of periodic fasting did not harm healthy Austrians

But they improved the condition of their hearts and blood vessels and influenced blood tests

Polina Loseva, "The Attic"

Doctors have been using different fasting techniques for a long time to combat obesity, diabetes or the consequences of severe operations. However, doctors usually do not recommend starving healthy people for fear of side effects. Researchers from Austria, Switzerland and the USA conducted the first clinical trial on healthy people, in which they applied one of the most stringent methods – periodic fasting. According to this method, 12 hours of food alternated with 36 hours of hunger. Doctors did not find any dangerous side effects in the participants of the experiment. But many health indicators, which are often associated with a long life, have changed for the better.

Calorie restriction has long been the gold standard in prolonging life: all other methods are now evaluated in comparison with it. But whether this method works on humans is still unknown, because it is very difficult to set up a competent experiment. In order to somehow track how starvation affects the human body, researchers set up short experiments, literally several months or years long. During this time, you can check whether any indicators of human health or his biological age are changing.

But there is another difficulty with experiments in gerontology: aging is still not recognized as a disease, so possible methods of prolonging life are rarely tested on healthy people. Calorie restriction, for example, has been repeatedly tested on overweight or diabetic people, but there are practically no studies on healthy volunteers. The largest of them, CALERIE, is testing a classic technique according to which doctors limit the participants in the experiment in daily calorie intake by 25% (compared to the baseline level, which is enough for saturation). However, its participants have not yet been able to achieve the required degree of fasting, in two years they have reduced consumption by only 12%.

Scientists from Austria, Switzerland and the USA conducted another fasting test on healthy people. They tested the method of periodic fasting, which is considered one of the toughest: 36 hours of complete hunger (you can only drink unsweetened drinks) alternated with 12 hours when the subjects could eat fully. Two groups participated in the study. One is 30 people who practiced periodic fasting even before the experiment began for six months. Their state of health was compared with 60 volunteers, who were then also divided into two groups – control and experimental. The second was ordered to starve periodically, for one month. 

Judging by the daily reports of the participants, they were able to reduce their calorie intake by an average of 37% (spread from 24 to 48%). This is quite a lot, if we remember that the participants of CALERIE could not overcome even the 12 percent bar. This figure is closer rather to the Minnesota experiment of the mid-20th century, during which young men consumed half as much energy as they spent. However, this experiment ended quite quickly when the participants began to have health problems. 

Therefore, the authors of the new study were primarily interested in possible side effects from fasting. Despite the fact that calorie restriction can prolong the life of a variety of organisms, doctors recommend treating it with great caution. Among the side effects may be not only weight loss (which is not always favorable), but also, for example, a decrease in bone density, which can lead to fractures, or suppression of immunity. However, the authors of the work did not find any serious side effects.

Of course, it is impossible to measure the rate of aging of the participants in the experiment under such conditions – for this it would have to count how many of them died during the study. But during the four months of the study, this, fortunately, never happened. Instead, the authors evaluated other indicators of the subjects' health, which are often associated with longevity. For example, the state of the cardiovascular system: it improved in about the same way as in experiments with constant calorie restriction. In addition, the subjects decreased the amount of thyroid hormones and the amino acid methionine in the blood, which often occurs in animals during life extension experiments. But the concentration of unsaturated fatty acids has increased (these include omega-3 and omega-6 acids), which mitigate inflammation, and ketone bodies (as with a ketogenic diet), which are considered indicators of a healthy metabolism.

Despite the fact that this work has a number of drawbacks: the sample is small, it is difficult to compare groups with each other, and the scientists did not control the composition of the food in any way – this is another important step in the study of fasting. However, at the end of the article, the authors of the work still recommend: do not start starving without consulting a doctor.

Article by Stekovic et al. Alternate Day Fasting Improves Physiological and Molecular Markers of Aging in Healthy, Non-obese Humans published in the journal Cell Metabolism.

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