Our brain is very well fenced off from all the chemistry that floats in the blood. This is called the blood-brain barrier.
There are weak points in this barrier. There, various biologically active substances penetrate the brain and do something with it. This usually happens in the hypothalamus. We have already discussed the hypothalamus in the topic about body temperature regulation. There, different chemistry raised or lowered our temperature.
So, in terms of appetite regulation, different hormones from the blood like insulin and leptin also act on the hypothalamus. This is normal.
It turned out that the bile acids that are produced in our liver float in the bile and help to digest fats, so they also manage to get into our brain and beat off appetite.
We have already discussed bile acids in the topic about poor food digestion and agreed that after digestion, bile acids should normally be absorbed into the bloodstream and return to the liver.
The trick is that after absorption in the intestine and before it gets back into the liver, bile acids are in the blood for some time. With blood, they swim to the hypothalamus, overcome the blood-brain barrier and discourage our appetite. That is, they act like hormones.
The most interesting thing is that this cunning natural mechanism works only when a person does not abuse fat. If only he begins to overeat, then all this delicate balance with bile acids is disturbed. All bile acids are directed only to the digestion of food and already affect any appetite.
That is, it confirms the fact that once you start eating fatty foods on a regular basis, then it is very difficult to stop.