Introduction
Many people believe that weight gain and loss are the results of calories and willpower, but studies have proven that a hormone called leptin is also involved. This hormone helps maintain the normal weight of a person, where the level of leptin in the blood is directly related to the body fat a person contains. Leptin resistance causes the person to feel hungry and eat more even though the body contains enough fat storage.
What Is the Leptin Hormone?
Leptin is a hormone released by the adipose tissue (body fat) to maintain a normal weight in the long run. It does this by stimulating hunger pangs and providing the sensation of feeling full. Hormones are chemicals that help to coordinate various body functions by carrying messages through the blood to the organs, muscles, and other tissues. These signals inform the body what to do and when to do it.
What Are the Uses of the Leptin Hormones?
Leptin is usually known as the ‘satiety hormone’ or ‘starvation hormone.’ Its primary target is the hypothalamus which is present in the brain. This hormone sends information to the brain regarding the amount of fat stored in the body. It also significantly affects fertility, immunity, and brain function. The main use of the leptin hormone is the long-term regulation of energy, which includes the number of calories a person intakes and expands and how much fat is stored. Leptin hormones prevent people from starving and overeating, where both conditions can cause issues.
Leptin does not affect the hunger level and food intake; rather causes some changes in food intake and controls energy expenditure over a long period, regulating the normal weight. Leptin has more effect when a person loses weight; as the body fat decreases, the leptin also reduces, which signals the body to think it is starving. It results in intense hunger appetite leading to more consumption of food.
What Is the Impact of Leptin on the Brain?
The adipose tissue produces leptin hormone; the more body fat, the more leptin production. The bloodstream carries it to the brain, where it signals the hypothalamus, a part of the brain that controls when and how much to eat. The fat cells present give the information to the brain on how much fat they carry. Therefore, a high level of leptin indicates plenty of stored fat, whereas a low level of leptin indicates a low level of fat that the person needs to eat.
When a person eats, the body fat increases, which leads to an increase in the leptin level; thus, the person eats less and burns more. In contrast, when the person is starving, the body fat decreases, which results in a drop in leptin level; at this point, a person eats more and burns less. This system is called a negative feedback loop, similar to many physiological functions like breathing, body temperature, and blood pressure.
How Is Leptin Controlled?
The adipose tissue, which releases leptin, is a major type of fat in the body that is present beneath the skin, around the internal organs, and in the middle cavities of the bone. It provides cushioning effects for various parts of the body. The amount of leptin in the body is directly related to the amount of adipose tissue. Leptin level increases if the fat mass increases, and leptin decreases if the fat mass is reduced over time.
Which Test Is Used to Measure Leptin Level?
Usually, a blood test is performed to determine the amount of leptin in the blood. A leptin test is not generally performed; it is done only if someone is obese and has persistent hunger or a young child with class III obesity.
What Are the Normal Levels of Leptin Hormone?
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Adult Assigned as Female at Birth: 0.5 to 15.2 nanograms per milliliter.
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Adults Assigned as Male at Birth: 0.5 to 12.5 nanograms per milliliter.
What Happens When There Is an Increased Level of Leptin?
As leptin level increases only when the number of adipose tissue increases in the body, it results in obesity with an increased level of leptin (hyperleptinemia). It can also result in leptin resistance, which is the lack of sensitivity to leptin.
Other Conditions Related to Hyperleptinemia Are:
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Nonalcoholic fatty liver disease.
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Rabson-Mendenhall syndrome.
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Neurodegenerative disorder.
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Depression.
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Food addiction.
What Is Meant by Leptin Resistance?
Leptin resistance is a condition where the brain does not respond to leptin as it normally does. As it is constantly triggered by leptin, the person does not get the sensation of feeling full, which results in overeating even though the body contains enough fat stores. A lack of leptin in case of leptin resistance leads the body into a starvation mood. To save energy, the body reduces energy levels and allows the person to use fewer calories at rest. Leptin resistance results in obesity and weight gain in the form of stored fat by stimulating hunger and reduced metabolism.
What Are the Signs and Symptoms of Leptin Resistance?
Leptin resistance is caused due to reduced ability of leptin to suppress appetite or increase the use of the body’s energy. Due to this, the main symptom of leptin resistance is constantly feeling hungry and increased food intake despite having an adequate or excess amount of stored fat.
What Causes Leptin Resistance?
1. Inflammation:
Inflammatory signals in the hypothalamus are an important cause of leptin resistance.
2. Free Fatty Acids:
Increased free fatty acids in the bloodstream may enhance the metabolism in the brain and disturb leptin signaling.
3. Having High Leptin:
Increased leptin levels can result in leptin resistance.
How Can Leptin Resistance Be Reversed?
Certain things can reverse leptin resistance:
1. Avoid Processed Food:
Highly processed food may impair the integrity of the gut and cause inflammation.
2. Eat Soluble Fiber:
Eating soluble fiber improves gut health and protects against obesity.
3. Exercise:
Any physical activity helps to reverse leptin resistance.
4. Sleep:
Poor sleep is associated with problems with leptin.
5. Reduce Triglycerides:
Increased triglyceride interferes with leptin transport from the bloodstream to the brain. So the best way is to reduce carb intake, which reduces triglycerides.
6. Eat Protein:
High protein intake results in weight loss, leading to reduced leptin sensitivity.
What Happens When There Is a Reduced Leptin Level?
It is normal to have hyperleptinemia (low leptin level), also called congenital leptin deficiency (a genetic condition that prevents adipose tissues from releasing leptin). Without leptin content, the body thinks it has no fat, which signals intense hunger and food consumption. Thus, congenital leptin deficiency results in class III obesity in children and delays puberty. It is also related to the following conditions:
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Frequent bacterial infections.
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Hyperinsulinemia (high insulin production).
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Fatty liver disease.
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Dyslipidemia (imbalance in lipids, including cholesterol and triglycerides).
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Hypogonadotropic hypogonadism (low level of sex hormones).
Conclusion
Leptin is a hormone that regulates the weight of a person. These leptin hormones are produced in the adipose tissues. The leptin hormone signals the hypothalamus of the brain, which provides information about the amount of fat stored. Leptin resistance is a condition where the brain does not respond to leptin, resulting in increased weight gain and obesity. Low leptin level causes starvation and leads to overeating despite the adequate amount of stored fat. However, leptin levels can be maintained through some changes in lifestyle and diet.
