Leptin – The hormone telling you you’ve had enough

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A growling stomach, a feeling of fatigue, and thoughts more concerned with the fridge than with the rest of your day — all of these are clear signs that you’re hungry. But how do you know when you’re full and that you’ve provided your body with enough food? In addition to giving you that pleasantly filled stomach and recharged energy, your central nervous system also controls a feeling of satiety. The hormone leptin tells you when you should stop eating. How exactly does it work? Let’s find out.

What is leptin?

Before we look at what happens when you eat, let’s take a closer look at the hormone leptin. Leptin is a peptide hormone, or, more precisely, an adipokine. Synthesized in the human body, the active hormone is composed of 146 amino acids. As an adipokine, the hormone is mainly produced in adipose (fat) cells before it’s released. Small amounts are also produced in bone marrow, skeletal muscles, stomach lining, and skin cells.

Incidentally, leptin was only discovered in the 1990s, and has been the subject of numerous scientific studies since. Among other things, the great interest in this research is due to the steadily increasing average weight of the global population, despite functional levels of leptin. 

The function of leptin 

Every day you listen to your body – sometimes consciously and sometimes unconsciously – to find out whether you are hungry. If you answer yes, you might sip on a creamy chocolate shake with banana in the morning, for example, or perhaps decide on a low-carb Buddha bowl for lunch. A slice of vegan banana bread is enough to give you a little energy boost as a pick-me-up in the afternoon. 

a photo of deep brown vegan banana bread, which can help you produce leptin when you feel full

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At the end of every meal, you eventually decide that you’re full and put down your fork. The physiological system behind it follows a clear system. In a healthy person, leptin levels are what regulate the body’s total energy stores. As the stomach fills up, the fat cells eventually send out leptin to signal, “We are full!”

Leptin is produced in the fat cells. So if there are many fat cells in your body, a lot of leptin is released – and vice versa. The hormone leptin first circulates in the blood and then stimulates two groups of receptors in the hypothalamus: one group of neurons produces transmitter substances that have an appetite-suppressing effect, and the other group produces appetite-stimulating neuropeptides. 

Leptin and its counterpart, ghrelin 

We know that leptin is responsible for feeling full. But which hormone is important when it comes to signaling hunger? The answer: the peptide hormone ghrelin. Ghrelin is produced in the cells of the stomach lining when the body’s desperate for a food intake. During these hunger phases, the ghrelin level in the blood rises. After eating, it drops again. Makes sense, no?

Leptin Resistance 

Sometimes one portion of pasta becomes two, a single cookie becomes half a package, and a piece of chocolate magically morphs into the whole bar. In everyday life we often lack the time for a conscious meal. It is not uncommon to notice your body’s hunger signals, but ignore its satiety signals and eat beyond your hunger level and thus exceed your energy requirements. If this happens more frequently over a longer period of time, it results in weight gain. 

The hormone leptin is a natural appetite suppressant for people with a healthy body weight. In overweight people, however, the signaling of the feeling of satiety no longer works, which leads to leptin resistance. Despite high leptin levels, which are present in the body due to the high level of fatty tissue available to produce leptin, individuals affected by leptin resistance no longer feel a healthy feeling of satiety.

The exact physiological development of leptin resistance in people with obesity has yet to be adequately researched. Based on various studies, however, it is believed that through long term weight loss and the help of a balanced food intake and sufficient exercise, leptin sensitivity in the brain can be restored. 

Leptin as medication

Before studies showed that overweight people do not suffer from leptin deficiency but rather from leptin resistance, a leptin-like substance was used for treatment. Now, overweight people and patients with Type II diabetes due to obesity have the task of regaining its function through weight loss.

Did you know that people with intuitive eating habits tend to be healthier? The principle of intuitive eating is to listen to the body in order to understand its needs. If you are interested in this topic and you want to know more about it, you can have a look at our article on Intuitive Eating.

People suffering from lipodystrophy have a very low production of leptin due to a congenital lack of fat cells. In the case of this very rarely occurring disease, the drug metreleptin is used. The protein is an analogue of human leptin and is responsible for signaling a feeling of satiety. 

Leptin as appetite suppressant 

It can be claimed that leptin, as a natural appetite suppressant, plays a fundamental role in maintaining a healthy body weight. For people with obesity, the logical conclusion seems to be that an extra intake of leptin in the form of a drug or dietary supplement should also help them to control their appetite and maintain a healthy body weight. But can leptin really help you lose weight? We know that the problem is not a low leptin level, but the reduced sensitivity of our brain cells to leptin levels. Therefore, according to current scientific knowledge, it can be assumed that overweight people and patients with diabetes do not necessarily benefit from an additional leptin intake. 

Leptin: Summary 

Too much information at once? No problem. Here are the most important facts at a glance. 

  • The adipokine leptin, which is mostly produced in the fat cells, signals to you as a satiety hormone when you have sufficient energy available.
  • The release of this hormone has an appetite-suppressing effect
  • The counterpart of leptin is the hunger hormone ghrelin
  • People who suffer from obesity or even diabetes no longer feel a healthy sense of satiety despite high levels of leptin. 
  • The reduced sensitivity is likely to be regained when a healthy body weight is reached. 
  • Leptin is a natural appetite suppressant, but taking a leptin-like substance only has a significant effect in patients with lipodystrophy.

Sources for this article

We at foodspring use only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial policy to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

  • Theodore Kelesidis et. al (2010): Narrative Review: The Role of Leptin in Human Physiology: Emerging Clinical Applications https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2829242/  
  • AMBOSS Fachwissen für Mediziner
  • Bundesministerium für Bildung und Forschung – Gesundheitsforschung 
  • Ärzteblatt
  • Diabetesinformationsdienst München