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Leptin: Definition And Function Of This Fat-Burning Hormone

The leptin hormone regulates fat levels and signals the brain to suppress the feeling of hunger.
Leptin is a peptide known as the fat-burning hormone.



Leptin comes from the Greek word “leptos”, which means “thin”. As you may think, this is a hormone that regulates body weight by controlling hunger and burning fat.

The wonder diets have seen in the modification of this hormone a useful tool and a great hope to lose weight. But, is this fat-burning hormone actually so effective? How does leptin function?

What is leptin?

Leptin is a peptide, i.e. a substance made of amino acids, and produced by various types of tissue, but mainly by adipose tissue, which is body fat. That is to say, it is a mixture of amino acids produced by fat cells. Its main function is to report the levels of fat.

However, the importance of leptin was discovered a few years ago, when a study of a Dallas institute, in the United States, showed that injecting animals with this hormone reduced their appetite and burned high amounts of fat.

LBody weight regulation and body capacity are related to energy balance. Hence, researchers found that the guinea pigs used for the experiment had reduced a quarter of their body weight, decreasing adipocytes and increasing mitochondria, which are known as the powerhouses of the cells.

That is, when it comes to weight imbalances, this hormone reduces the unnecessary fat but maintains, and even increases, the energy stores.

Not only that, but other studies have shown that mice injected with leptin from birth grow up with a resolution in their brains to regulate hunger. It sounds like a magic remedy, but let’s see if it is that easy.

How does leptin function?

The human body is a very intelligent structure, and there are things that will never cease to surprise us. For example, the way in which leptin, this fat-burning hormone, manages to regulate hunger is really amazing.

In order to understand it better, you have to think of leptin as a fat regulator which constantly sends signals to the brain about the levels of body fat. When these levels are about to become saturated, this hormone informs the central nervous system that you have already eaten enough, so it suppresses the feeling of hunger.

Since obesity has become one of the main concerns in Western countries, the studies on body metabolism regulation have increased. One of the conclusions drawn is that, when there is an increase of body fat, leptin acts on the hypothalamus, in the central nervous system, to reduce appetite. That is why it is known as the fat-burning hormone.

Leptin is secreted in the blood stream by the adipose tissue, the stomach and some liver cell. In fact, it is not only found in these tissues, but also in peripheral organs, which is why its functions increase.

Leptin regulates body weight by controlling hunger and burning fat.


Is leptin actually a magic remedy?

The studies carried out by several medical centres seem to follow an overwhelming logic: if great amounts of this hormone are injected, hunger will be reduced and fat will be burnt, reaching a perfect balance without suppressing energy stores. More leptin means less hunger.

However, there are quite a few experts who deny such argument. They point out that there is no conclusive study that shows the effectiveness of injecting human beings with leptin, and they indicate that there are still many questions to be answered. For example, what are the dangers involved in the increased levels of this fat-burning hormone in the body?

What has been demonstrated are the dangers of hyperleptinemia, which is an excess of leptin in the body that creates the opposite effect, i.e. obesity. For many experts, the use of leptin as a magic remedy for weight loss is nothing more than a commercial strategy for selling dietary products.

Leptin acts as a natural regulator of the body suppressing the feeling of hunger when the fat stores become saturated. Therefore, it would be inappropriate to change artificially the levels of leptin. According to those who oppose its medical use, weight loss should be done naturally and taking into account the energy balance.

Fun facts

Apart from the functions that have already been explained, the leptin hormone performs other tasks in the human body. Among its fun facts, you will find out why it lies at the root of some obesity problems.

1. Is leptin resistance the cause of obesity?

As it has been mentioned before, an excess of this hormone in your body can have the opposite effect. When leptin levels are very high, the central nervous system stops responding to its signals and the brain understands that, far from losing appetite, the body demands more energy stores, and increases the feeling of hunger.

Studies show that obese people have four times more leptin than the non-obese, which indicates that leptin resistance is one of the causes of morbid obesity.

An excess of leptin in the body creates the opposite effect and increases the feeling of hunger.


2. Leptin levels increase during pregnancy 

Apart from the adipose tissue, stomach and liver, leptin is also synthesised by the placenta during pregnancy and it is secreted into the maternal circulation. This means that leptin levels increase during pregnancy, especially in the second and third trimester.

3. Does leptin causes hypertension?

It has been showed that this hormone stimulates the antiangiogenic function of the body, which forms new blood vessels. This happens during the embryonic stage, the growth or when you have a wound, as a regenerative healing factor. Leptin can also increase blood pressure.

Another issue to be demonstrated is whether the excess of leptin in obese people is also the cause of blood pressure.

4. Can leptin stop blindness caused by diabetes?

This has not been demonstrated yet, but there is the hypothesis that leptin can be an effective remedy for slowing down vision disorders caused by diabetes mellitus. What has been demonstrated is that leptin changes some functions of the eye. Therefore, its ability to form new blood vessels could help the regenerative process.

In this case, it would always be a therapeutic support, not a final solution.

5. The importance of leptin during puberty

At a sexual level, the close connection between leptin and the hypothalamus is essential for the beginning of the puberty process and sexual maturity. That is to say, leptin signals the brain that there are enough fat levels to begin the female puberty process and reproduction.

It has also been discovered that it participates in the production of testosterone and that, in obese women, it can be the cause of amenorrhoea (menstrual pain).

Check out the original article: Leptina: qué es y cómo funciona esta hormona quema grasa at



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