Every day we neglect the philosophical and gastronomic wisdom proclaimed by Socrates: “You need to eat to live, not live to eat.” What makes a person neglect natural, naturally given signals (“I am full, I don’t want to eat anymore”) in favor of overeating for pleasure that is harmful to the body?
When obese people see high-calorie foods, large-scale areas responsible for pleasure, attention, emotions, memory and motor skills are activated in their brains, studies using functional magnetic resonance imaging have shown. It remains unclear why people get fat: because their body is not capable of self-regulation of weight, or because the body loses this ability when gaining excess weight.
The process of digestion, as you know, begins even before the food enters the stomach and even into the mouth. The sight of food, its smell, or even the word that calls it, stimulate the areas of the brain responsible for obtaining pleasure, they activate the memory centers and salivary glands. A person eats even when he does not feel hunger, because it gives pleasure. What makes a person neglect natural, naturally given signals (“I am full, I don’t want to eat anymore”) in favor of overeating for pleasure that is harmful to the body?
Scientists from Columbia University (New York) presented a paper on the physiological causes of overeating at the congress on obesity in Stockholm.
Detailed mapping of brain activity has shown how the prospect of enjoying delicious food defeats the body’s natural ability to regulate weight and protect against overeating.
Scientists dubbed such types of nutrition “hedonic” and “homeostatic” respectively (homeostasis is the body’s ability to self-regulate, maintain dynamic balance). It turned out, in particular, that the brain of overweight people reacts more “hedonistically” to sweet and fatty foods than the brain of people with normal weight. The brain of overweight people reacts violently even to images of tempting food.
Physicians studied the reaction of the brain to “appetizing” images using functional magnetic resonance imaging (fMRI). The study involved 20 women – 10 overweight and 10 normal. They were shown images of tempting food: cakes, pies, french fries, and other high-calorie foods. MRI scans showed that in overweight women, the images had extremely active brains in the ventral tegmental area (VTA), a small point in the midbrain where dopamine, the “neurohormone of desire,” is released.
“When overweight people see a high-calorie meal, large areas in their brains are activated that are responsible for feelings of reward, attention, emotions, memory and motor skills. All these areas interact, so it is difficult for natural self-regulatory mechanisms to resist them, ”explained Susan Carnell, a psychiatrist at Columbia University.
In the control group – slender women – such reactions were not observed.
Increased appetite in overweight people was caused not only by images of food. Sounds, such as the words “chocolate cookie” or the names of other high-calorie treats, elicited similar brain responses. The sounds of words for healthy, low-calorie foods, such as “cabbage” or “zucchini,” did not elicit this response. The brain of slender women reacted weakly to “delicious sounds”.
A similar study was presented at a nutrition conference in Pittsburgh. Neurologists from Yale University conducted an fMRI study of the brains of 13 overweight and 13 slender people. Using a scanner, brain responses to the smell or taste of a chocolate or strawberry milkshake were recorded. The reaction of the brain of overweight people to food was observed in the region of the amygdala of the cerebellum – the center of emotions. They “experienced” delicious food whether they were hungry or not. The cerebellum of people with normal weight reacted to a milkshake only when a person experienced a feeling of hunger.
“If your weight does not exceed the norm, the mechanisms of homeostasis work effectively and successfully control this area of the brain. However, if you are overweight, there is some kind of dysfunction of the homeostatic signal, so overweight people succumb to food temptations, even when they are completely full,” said study leader Dana Small.
A “diet” of sugary and fatty foods can completely blunt the built-in mechanisms of weight regulation in the human body. As a result, the digestive tract ceases to produce chemical “messages”, in particular the protein cholecystokinin, which “reports” satiety. This substance must go to the brainstem and then to the hypothalamus, and the brain must give the command to stop eating. For obese people, this chain is interrupted, therefore, they can regulate the duration and abundance of the meal only from the outside, by a “volitional decision”.
One important thing is not clear from the studies that have been done, in the spirit of “which came first, the chicken or the egg.” Do people get fat because their body is initially incapable of self-regulation of weight, or does the body lose this ability when gaining excess weight?
Dr. Small believes that both processes are interrelated. First, a violation of the diet causes a dysfunction of the homeostatic mechanisms in the body, and then a metabolic disorder provokes an even greater development of fullness. “It’s a vicious circle. The more a person eats, the more they run the risk of overeating more and more, ”she said. By investigating the implications of fatness in brain signaling, scientists hope to fully understand the “fullness centers” in the brain and learn how to regulate them from the outside, chemically. Hypothetical “slimming pills” in this case will not directly lead to weight loss, but will restore the body’s natural abilities so that it recognizes the state of satiety.
However, the best way not to disrupt these mechanisms is not to start getting fat, doctors remind. It’s better to immediately listen to the body’s signals “enough!”, and not succumb to the temptation of drinking tea with cookies and cake, and indeed to reconsider your diet in favor of low-fat and easily digestible food.