Many people feel that they cannot control their appetite in these circumstances . They know what foods suit them, but they eat others. If they manage to diet to lose weight, they gain it back quickly. Appetite overcomes reason.
What would a "natural" appetite look like?
Many experts believe that if today's excess appetite seems like a problem, at another time, at the beginning of human history, it was an advantage.
When there was a shortage of food, the feeling of endless hunger encouraged people to look for it, and when a good quantity was found—for example, when hunting a large animal— they should not be satisfied with a small serving. It was not known how long it might be until the next banquet.
Namely, we were and still are because genetically, we are the same, programmed to eat and eat, especially high-fat foods.
In the past, it was necessary to accumulate maximum energy . According to Jeffrey flierobesity researcher at Harvard University School of Medicine, people with the most incredible ability to eat were the ones most likely to survive.
Still, cravings rarely rise to the level of rampant insanity. The body does not get fat quickly and without limits. Most people with overweight have gained their kilos slowly, perhaps at the rate of a kilo per year . This means that the body has a remarkable ability to keep itself in balance.
A person who consumes 2,365 calories daily (900,000 calories per year) and increases your weight by a kilo of fat -equivalent to about 8,000 calories- could have prevented that increase by reducing your intake of 22 calories daily, that is, a teaspoon of sugar or two chips.
Most people feel hungry three times a day. They coincide exactly with meal times, determined by the cultural environment . An Englishman is hungry at one in the afternoon and a Spaniard at half-past two.
The hunger hormone
The hormone involved in the sensation of appetite, ghrelin, was discovered very recently, in 1999, and is known to be secreted in the stomach and intestine by seeing or smelling food or in response to time habits.
David E Cummings from the University of Washington (United States) has measured the ghrelin levels in the blood every 20 minutes and has verified that they vary as mealtime approaches .
Ghrelin stimulates three areas of the brain:
the cerebellum, which controls unconscious automatic bodily processes;
the hypothalamus, which governs metabolism;
and the mesolimbic center where pleasurable sensations are processed.
Although ghrelin is one of the substances most specifically related to appetite, regulating it is not its only function. It also turns out essential in growth, learning, and adaptation processes to changes in the environment.
Several studies confirm that people with constant appetite and obesity have lower blood ghrelin levels than people of optimal weight. These increases before meals and drop to 40% after.
There is hardly any variation in overweight people that explains that their appetite does not disappear.
It is also known that anorexics have permanently elevated levels. The body cries alarm through ghrelin that these patients have learned to ignore.
Why do we feel complete?
Ghrelin is an appetite stimulant, but it is not its only regulator. The body has a natural hunger break system .
Its first component is nerves that sense distention of the stomach and intestines and warn the brain that they are already full.
This message is reinforced by three substances that travel to the head from the intestine.
The first is a peptide, a short chain of amino acids released from the small intestine called cholecystokinin (CCK). The more immediate action makes us get up from the table feel full.
But CCK wears off quickly, and we'd sit back again if it weren't for other substances that contribute to the feeling of satiety . These are the hormones GLP-1 and PYY which consider the food settled until further notice.
They are produced in the large intestine and not only tell the brain that enough has been eaten but stop stomach activity so that no more food is sent to the intestine, where the natural digestion takes place.
In addition, GLP-1 adjusts blood chemistry, stimulating the pancreas to release more insulin, which soaks up the sugars that reach the blood and stores the surplus in the body's fat stores.
The function of these hormones goes beyond the moment of ingestion because they are involved in the administration of the energy obtained .
If the person insists on continuing to eat despite all the restraints, the body has a third resource: leptin .
Discovered in 1994, it is the appetite-suppressing hormone . It is produced by own body fat and travels through the blood vessels to the same places in the brain where ghrelin acts: it suppresses hunger by occupying the cellular receptors for the appetite hormone.
The discovery of leptin made some scientists believe that obese people did not produce enough and that, if injected, the affected person would stop eating and burn their fat reserves. But things were not so easy.
The analysis showed that the obese, except in exceptional cases, produced the leptin corresponding to them. The problem, it seems, is that obese people somehow become desensitized to their satiety hormones.
The definitive and straightforward way to regulate appetite has not yet been found because ghrelin, leptin, and the other gut hormones are only part of the very complex control system.
At least a dozen other hormones and peptides have been found to play a role, such as a neuropeptide Y (an appetite stimulant that is segregated under stress conditions ) or the r-Agouti protein, which also with a stimulating effect.
The control center: signals of hunger and satiety
Thus, how the characteristics of appetite develop is still essentially a mystery.
It's known that you are not born with a preprogrammed appetite . He begins to collect a form from early childhood when making contact with flavors, and specific sensory, metabolic, and neurochemical networks develop.
It is also known that the sensation of appetite coincides with the activation of the mesolimbic region in the center of the brain, the area where pleasurable sensations are processed.
They come from there the signals that through the vagus nerve reach the stomach , which begins to secrete gastric juices. The pancreas starts to produce insulin. The liver starts up to receive carbohydrates and fats.
While this complex process unfolds, consciousness is filled with a simple idea: "I'm hungry."
Researchers from around the world are observing the brain to discover in which areas appetite is felt and satisfied or what are the receptors on the surface of the neurons on which the sensations of hunger and satiety depend. They also study the signals from nerve networks in the stomach and intestines .
