This article is taken from the monthly Sciences et Avenir – La Recherche n°904, dated June 2022.
Eat better to live longer? What if we had to eat less above all? In any case, this is what a study by Yale University (New Haven, United States) suggests. Published in February, it is the first to demonstrate the positive effects of calorie restriction in humans. Until now, the method had only shown its effectiveness on animals. And still little ones: flies, mice or worms. Or species whose existences are short enough to be studied in their entirety in the laboratory. In these animals, reducing the quantity of calories ingested makes it possible to increase life expectancy. Sometimes very significantly: 50% more life for certain primates such as mouse lemurs. Spectacular results are also obtained if animals are fed at specific times of the day and not at other times. (read box below).
But other experiments, still in mice, had shown that calorie restriction increased infections. Unable to conduct studies over several years with many human participants, the American team led by Vishwa Deep Dixit, director of the Center for Research on Aging at Yale, attempted an experiment with 200 volunteers. Half of them did not have to change anything in their eating habits. The hundred others had to reduce their calorie intake by an average of 14%. All the participants had to carefully note their menus, the quantity of what they ingested, for two years.
This article is taken from the monthly Sciences et Avenir – La Recherche n°904, dated June 2022.
Eat better to live longer? What if we had to eat less above all? In any case, this is what a study by Yale University (New Haven, United States) suggests. Published in February, it is the first to demonstrate the positive effects of calorie restriction in humans. Until now, the method had only shown its effectiveness on animals. And still little ones: flies, mice or worms. Or species whose existences are short enough to be studied in their entirety in the laboratory. In these animals, reducing the quantity of calories ingested makes it possible to increase life expectancy. Sometimes very significantly: 50% more life for certain primates such as mouse lemurs. Spectacular results are also obtained if animals are fed at specific times of the day and not at other times. (read box below).
But other experiments, still in mice, had shown that calorie restriction increased infections. Unable to conduct studies over several years with many human participants, the American team led by Vishwa Deep Dixit, director of the Center for Research on Aging at Yale, attempted an experiment with 200 volunteers. Half of them did not have to change anything in their eating habits. The hundred others had to reduce their calorie intake by an average of 14%. All the participants had to carefully note their menus, the quantity of what they ingested, for two years.
Eat on time
Snacking at all hours, we know, promotes weight gain and obesity. For a simple reason: eating at fixed times allows the body to prepare for it by secreting gastric juices in advance and thus digesting more efficiently. Confirmation with the work of an American team from the Howard Hughes Medical Institute, at Chevy Chase, published in Science May 5. Hundreds of mice were scrutinized for four years. Result: those who were fed caloric restriction during the night – a period of intense rodent activity – saw their lifespan increase by 35%. That’s three times more than those subject to calorie restriction alone during the day! The time at which we eat therefore seems to be as important, if not more so, than the quantity ingested. In any case, respecting the physiology and chronobiological parameters of a subject seems essential…
The thymus, producer of lymphocytes, regenerates
The scientists wanted to know what the consequences of a reduced diet were for the human immune system. They then analyzed the thymus, the gland above the heart that produces T lymphocytes, the white blood cells essential for our defense. Unfortunately, the thymus is a gland that does not age well. It is estimated that when an individual reaches their forties, two thirds of their thymus are already out of order. Consequence: the older we get, the less our body is able to fight against pathogens.
Using an MRI, the researchers were able to determine if there were any structural differences between the thymuses of the volunteers in each group. Undoubtedly, the gland of those who followed caloric restriction remained much more functional. She was even producing more lymphocytes than at the start of the study. Clearly, the thymus had regenerated, to the great surprise of Vishwa Deep Dixit and his team.
In their analyses, the researchers came across a particularly interesting gene: PLA2G7. Inactivated at the very beginning of caloric restriction, it gives a protein produced by cells of the immune system, macrophages. However, changes in the expression of PLA2G7 in participants under caloric restriction suggest that this protein could be strongly involved in the process. The proof is: by deactivating the PLA2G7 gene in mice, benefits were emerging similar to those of calorie restriction in humans, and especially on the good health of the thymus. “The goal of this research is the quest for a molecule that could have the beneficial effects of caloric restriction without the need to deprive yourself. “, analyzes Jérémy Terrien (CNRS / National Museum of Natural History of Paris).
No long-term negative effects
It does not appear, the researchers conclude in their article, that reducing calories in humans harms their immune system in the long term. Moreover, their work would even demonstrate the opposite, with the rejuvenation of the thymus. However, Jérémy Terrien notes two major biases in this study. “First of all, 65% of the participants are women. However, the two sexes have different reactions to these metabolic questions. If only because the female organism seems to process stress more effectively than that of men. oxidative which generates cellular damage.The second concerns overweight people who may have a different response to calorie intake.On these two points, the study lacks precision. “Nevertheless, enthuses the researcher, it highlights the primordial importance of a brain-gut interconnection, a field of research “Exploding! “The Yale University study also shows that a simple reduction in calorie intake, without being governed by a strict diet, is enough to have notable effects on our biology and our immune system. to what we eat but simply reducing the portions, already has benefits for our health…
