Saturated fatty acids increase appetite for several days
The leptin hormone and insulin play key roles in the mechanisms of appetite and food intake. In healthy people, leptin, which is secreted by adipose tissue, cancels the feeling of hunger and insulin, which is at its highest when blood glucose increases after a meal, causes the brain to decrease the taste of food .
A study, published in the September issue of the Journal of Clinical Investigation, shows that saturated fat interferes with the ability of the brain to respond appropriately to these signals.
Stephen Benoit, a researcher in behavioral neuroscience at the University of Cincinnati, and his colleagues found that after only three days of a diet high in saturated fat (found, for example, in beef and cheese), Rodent brain became resistant to leptin and insulin. Unsaturated fats, such as those contained in olive oil, did not trigger such resistance.
As a result of this resistance, a meal high in saturated fat increases appetite. "Taking leave of a healthy diet by eating fast food can have consequences that last a few days, even after you have resumed the healthy diet," says Benoit.
Feeling leptin and insulin is like keeping an eye on the state of nutrients in the body, says Gary Schwartz, a neuroscience researcher at Albert Einstein College of Medicine in New York, who is not involved in this research . "If that eye goes blind because too many nutrients are provided, it can not respond. (...) A vicious cycle of metabolic problems and weight gain can result.
Why does the body react like this? A possible explanation advanced by the researchers, inspired by an evolutionary approach, is related to the mechanisms involved in hunger. When a person is hungry, the body starts using its energy reserves. As a result, the blood becomes fat-fed, just as it does in the case of obesity and overeating. Cautious, the brain would interpret fat intake as a sign of starvation. "During evolution, humans have been facing a lack of calories and starvation much more than we have ever faced with an overabundance of calories," says William Banks of the St. Louis Veterans Affairs Medical Center. .
But, Benoit notes, a neurological response "that was helpful at some point in history is no longer useful when there is a McDonald's and a Taco Bell on the way home." So, in the battle against empty calories and obesity, "sticking to a Mediterranean diet, rich in olive oil and vegetables can help thwart the obsolete physiology of our brain."