One of the most common New Year resolutions is to lose weight or eat healthier, which in most cases involves undergoing a more or less strict diet. These dietary changes are commonly used as a tool to improve our physical appearance. However, as history shows, physical appearance and diets are determined by the culture of each era: we have gone from the standard of beauty established by the painter Rubens with his chubby women to the extreme thinness displayed by some models on today’s social media, without any of these standards being a reflection of ideal health. Numerous scientific studies show that changes in eating habits are a therapeutic tool. In recent years, diets that reduce calorie intake or temporarily cut down food consumption have been particularly studied. This is something that is not new to humanity, since many cultures establish fasting periods, although for different reasons.
The benefits produced by reducing the calories we ingest are based on the activation of the cellular recycling process, known as autophagy, whose main function is to remove the damaged components of our cells to keep them healthy. This would be something similar to the garbage collection or recycling services that are responsible for removing the waste we produce. When these services work well, the city is clean. If they stop working, trash accumulates and our quality of life decreases. Well, this is autophagy, our body’s garbage collection and recycling service. The importance of autophagy for our health is such that the 2016 Nobel Prize in Medicine was awarded to one of its discoverers, Japan’s Yoshinori Ohsumi. Many other researchers have shown that when we get sick or when we age, harmful compounds accumulate and prevent the proper functioning of our body. Increasing autophagy helps eliminate these damaged components and restores the proper functioning of the body.
Numerous research teams are looking for strategies to activate autophagy and thus help eliminate harmful products. These days, caloric restriction, that is to say, reducing the amount of calories we ingest, is the most effective known tool. In fact, caloric restriction has been shown to improve health during aging by stimulating cell recycling, although studies have been conducted primarily in animal models. These animals reside in a protected environment where their feeding is controlled, and, in addition, contrary to what happens in the wild, they have a sustained food supply. These circumstances are far from the conditions in which people live.
The studies in humans, called clinical trials, have shown that caloric restriction can positively impact some of the diseases related to aging, mainly cardiovascular ones. However, it has not been possible to evaluate the long-term effects of these diets, since it is extremely difficult to establish these dietary changes as a routine. To put this in perspective, in Western countries people consume over 3,000 kilocalories each day per person. Following these diets would mean reducing almost 1,000 kilocalories a day, which would be like eliminating an entire meal from our routine. These types of restrictions can cause psychological problems or the well-known “rebound” effect when the diet ends. In addition, we must add factors that have nothing to do with calories, such as the importance we award food as a social tool, for celebrations, for creating new bonds... However, in recent years, various studies of this type have been carried out. The most important one, called CALERIE and carried out by a consortium of American universities, implemented a 30% reduction in daily calories, keeping participants with these restrictions from a few months to two years. The results showed an improvement in the health of the participants, mainly in metabolic markers such as weight loss, improved response to sugar, decreased blood pressure... Some patients even improved in aspects that at first seem to have little to do with diets, like memory. It should be noted that these clinical trials require a high level of professional psychological support over their duration. Following this type of diet without the help of qualified personnel (scientists, doctors, psychologists and nurses) is very complicated. This has a high cost and makes its application to the general population almost impossible, at least for now. The largest clinical trial currently underway, CALERIE 210, only reduces participants’ calories by 12%, and will extend over two years. The main results published so far indicate improvements in the cardiovascular system, without showing a negative impact on the mood of the participants.
The results obtained so far are very promising, but the psychological and social components are key when it comes to diet implementation. To facilitate these dietary changes, new strategies have been created: the two most famous are intermittent fasting, which consists of skipping meals for a day; and eating only two meals a day (breakfast and dinner), separated by long periods of fasting, but keeping the same calories, which is the most important difference compared to intermittent fasting. The effect of both diets, as well as that of caloric restriction, is the same: long periods of fasting increase autophagy, which helps eliminate waste that accumulates from day to day. In other words, fasting would somehow be a call for the cleaning shift to start working. Despite the promising results obtained in research models, there are currently no clinical studies that show that these new strategies reduce the signs of aging. The only reference to its long-term benefits is that of the inhabitants of an island in Japan, Okinawa, who traditionally maintain this regimen. When compared to the rest of Japan, the small island inhabitants were found to show much lower rates of age-related problems such as cancer, cardiovascular disease and diabetes. In addition, Okinawa is the place in the world with the highest rate of centenarians.
Although research models results show a beneficial effect of these diets on aging, much remains to be explored. More long-term clinical studies are needed to confirm benefits during aging, even more so considering the interpersonal differences and the social implications of diet in daily life.