- Leptin is a protein made in the fat cells of the body. It circulates in the bloodstream before entering the brain.
- The way leptin is supposed to work is by informing the brain that you are already full.
- Leptin resistance happens when leptin does not work as it should be.
What is leptin?
Leptin has been termed as "fat hormone", "obesity hormone", and in some cases, called as the "starvation hormone". Scientists discovered leptin in the year 1994, and with its discovery, there was a lot of excitement since it was regarded as the potential hit product for weight loss treatment.
There has been a common notion among people that weight gain or loss is all about how much calories we take in or cut off. Moreover, it also depends on the willpower and determination of individuals. However, scientists and studies suggest something else. According to studies, weight loss or gain is said to be associated with a certain hormone in our body called leptin. If an individual becomes resistant to the effects of this hormone, then it is thought to promote weight gain.
Today, some studies say that leptin is not an obesity hormone but rather a starvation hormone. Leptin is a protein made in the fat cells of the body. It circulates in the bloodstream before entering the brain. Its main target in the brain is the area called hypothalamus. It is the way the fat cells inform the brain that the energy thermostat is now set right, which means that it informs the brain that there is enough energy stored in the fat cells that can engage in normal metabolic processes of the body.
Normally, leptin levels are genetically stored at a certain threshold. However, when leptin levels exceed that threshold, the brain senses that the individual has enough energy stored. This would mean that one can burn energy and exercise at a normal pace, and also eat food in normal and moderate amounts.
Leptin can also engage in heavy processes such as puberty and pregnancy. Apart from these processes, the other functions carried out by leptin are fertility, boosts immunity, and proper functioning of the brain. However, its main role is regulating energy and balancing it by first identifying the amount of calorie intake as well as the amount of fat stored in the body.
During periods of starvation or dieting, an individual tends to eat less, which leads to fat cells losing some of their fat. This, in turn, decreases the production of leptin. Starvation leads to a decrease in the energy intake, which in turn leads to some weight loss. It then leads to leptin going below its threshold level. The brain then senses starvation and to revive the leptin levels back to the normal threshold, various processes begin in the body.
One of the processes involves the stimulation of the vagus nerve. This nerve normally runs in between the abdomen and brain. When the vagus nerve is turned on, it leads to feelings of hunger, which then leads the person to eat more, so that the body regains back the leptin threshold.
How does leptin work?
The way leptin is supposed to work is by informing the brain that you are already full. Its process is quite simple. As previously mentioned, leptin is produced by the fat cells of the body. This would mean that the more fat we carry in the body, the more leptin will be produced. Leptin is then carried through the bloodstream and then enters the brain.
While in the brain, it sends out a signal to the hypothalamus. The hypothalamus is the area of the brain that controls when we eat and the quantity of food we eat.
Fat cells use leptin to inform the brain on how much body fat they carry. If there is too much leptin produced, then it sends a signal to the brain that you have plenty of fat stored. On the other hand, lower levels of leptin would provide a signal that there is a low amount of fat stored and the body is at risk of starvation.
- When you eat, your body fat increases, which means that leptin is also increased. Hence, you burn more fat and eat less, avoiding unnecessary weight gain.
- When you do not eat much or in a diet mode, your body fat decreases, which would lead to low levels of leptin. Thus, you tend to consume more and burn less, which often lead to weight gain.
What is leptin resistance?
When it comes to animals, leptin is known to promote weight loss and satiety. However, in humans, it does not promote too much of weight loss. Hence, there is no foolproof method. Individuals who are obese tend to have high levels of leptin even though leptin is known to cause satiety. It suggests that leptin resistance leads to obesity in humans.
Leptin resistance happens when leptin does not work as it should be. It should either decrease one's appetite or cause an increase in energy levels. In today’s time, leptin is known to be the driver of weight gain among individuals. The fat cells present in our body are known to produce leptin, which should be in proportion to our size. Although people who are obese have high levels of leptin, it does not perform its job well leading to more weight gain.
Leptin Linked to Obesity
Individuals who are obese tend to have a lot of body fat stored in their fat cells. Since fat cells produce leptin, obese people tend to have high levels of leptin as well. However, leptin is not effectively functioning as it should, so people battling obesity tend to eat more and burn less fat.
Their brain should know that they have plenty of energy stored in the body. However, in such situation, the underlying issue is that leptin signal to the brain doesn’t work as it should be. The body has a host of leptin floating in the body, but the brain just doesn’t seem to recognize it. This is the condition that gives rise to leptin resistance.
Leptin resistance is now believed to be the main cause of human obesity. Since the brain fails to receive leptin's signal, it tends to erroneously process that the body is starving even if the body has more than enough energy stored in it. This changes our behavior and physiological patterns. To gain that energy or fat, which our brain thinks are missing in the body:
- We often tend to eat more because our brain tells us that we need to eat food to avoid hunger. Hence, there are some people who tend to feel that they are unnecessarily binging even after eating.
- Energy drops since the brain wants to conserve the body's energy. It makes us feel lazy and lethargic, resulting in burning fewer calories.
Therefore, eating more and having less exercise are not the only reasons for weight gain. It is also a hormonal defect or a consequence of leptin resistance.
What are the causes of leptin resistance?
There are many causes, which have been proposed to explain leptin resistance. It includes an impairment in the transportation of leptin and leptin's signaling issue. When it comes to the cerebrospinal fluid of obese individuals, leptin levels are slightly increased, which becomes the reason why leptin does not get into the brain much.
Individuals with high triglycerides can also impair leptin from getting into the brain. Another cause would be fewer leptin receptors. Leptin signaling cascade is also one of the causes why leptin does not enter the brain. Brain-derived neurotrophic factor (BDNF) levels are also impaired due to leptin resistance, which ultimately results in weight gain.
There are inflammatory signals in the hypothalamus that are known to be one of the important causes of leptin resistance in humans. Elevated leptin levels are also seen as one of the root cause of leptin resistance.
In some cases, there are free fatty acids floating in the bloodstream, which leads to an increase in the fat metabolites in the brain, thereby causing interference with leptin's signaling or communication with the brain.
The following are other factors that can also lead to leptin resistance:
- High levels of stress (physical, mental, or emotional)
- Sleep deprivation
- Consumption of foods containing fructose
- High levels of insulin
- Consumption of grains or lectin
- Too much exercise, especially when the hormones are already damaged
- Excessive consumption of carbohydrates
Treatment for Leptin Resistance
The best diagnosis to check for leptin resistance would be to check oneself in the mirror. They say the mirror never lies. If one has a lot of body fat, especially in the belly area, then the individual may be leptin resistant. There are several things one can do to reverse leptin resistance, few of which are mentioned below:
- Eat Less at Night: High levels of leptin leads to leptin resistance. The act of continuously eating without proper intervals causes a rise in the leptin levels. In such cases, it becomes harder to lose weight. Thus, individuals should take control of their diet and what should be eaten and at what time. There are people who don’t think much while eating unless they are starting to gain weight and come to the point of being overweight. They start to diet to lose that excess weight, which becomes quite a challenge. Eating too much of calories or increasing one's calorie intake can also lead to a rise in inflammation and fatty acids, which would again result in leptin resistance.
- Cut Down Sugar: Nowadays, there is a rise in a diet containing high sugar and saturated fat. These foods become crucial contributors to weight gain leading to obesity. Moreover, such diets have been known to cause inflammation in the hypothalamus, which would also promote the development of leptin resistance. Too much fat and carbohydrates in the diet can also lead to an increase in fatty acids. By reducing sugar and carbohydrates, there is also a decrease in the level of triglycerides, which is known to be one of the promoters of leptin resistance.
- Stay Active: Exercise has proven to be very beneficial in various ways when it comes to losing excess fats in the body. Apart from burning calories, it also improves the hypothalamic leptin sensitivity by suppressing hypothalamic inflammation. It is also known to lower the levels of triglycerides.
- Dietary Changes: One should increase the intake of protein in the diet from 15-30 percent. This would lead to a sustained decrease in the calorie intake, which can be mediated by increased leptin sensitivity in the brain and also lead to a reduction in weight gain of the individual. A diet low in carbohydrates coupled with regular exercise can also lower leptin levels and enhances an increase of adiponectin, which would ultimately lead to weight loss. One should consume large amounts of protein and healthy fats first thing in the morning as soon as they wake up. Protein is known to provide the body of the needed amino acids for the normal functioning of the body.
- Reduce Stress: Stress, whether acute or chronic, can also lead to weight gain. When you are stressed, your body releases the hormone cortisol, and high levels of cortisol can also cause leptin resistance. Thus, to keep weight gain at bay, one should relax and avoid being stressed all the time.
- Increase Soluble Fiber Intake: Studies reveal that consuming soluble fiber has shown multiple benefits in addition to improving gut health. Its regular consumption also protects individuals against obesity.
- Lower Triglycerides: A high level of triglycerides in the bloodstream is known to prevent the proper transportation of leptin from the blood to the brain. The only solution is to decrease the level of triglycerides in the bloodstream, which can be done by making certain dietary changes. Reduce your intake of sugar and other sources of carbohydrates to effectively lower your triglyceride levels.