Leptin, also called satiety hormone, is made by adipose (fat) cells that helps to regulate energy balance by controlling hunger. Leptin is opposed to the actions of ghrelin, called hunger hormone. Both hormones act on receptors in the arcuate nucleus of the hypothalamus to regulate appetite to achieve energy balance. The regulation of fat stores is deemed to be the primary function of leptin but it also plays in other physiological processes. Besides adipose cells, it is also produced by placenta, ovaries, skeletal muscles, stomach, mammary epithelial cells, and bone marrow.
It circulates in blood in free form and bound to proteins. Leptin levels in blood are higher between midnight and early morning, perhaps suppressing appetite during the night. The diurnal rhythm of blood leptin levels may be modified by meal-timing.
The following are important functions of leptin:
• Primarily, leptin regulates food intake and body weight. It acts on the specific receptors in the hypothalamus to inhibit appetite. When fat mass decreases, the level of plasma leptin falls so that appetite is stimulated until the fat mass is recovered. There is also a decrease in body temperature and energy expenditure is suppressed. Conversely, when fat mass increases, so do leptin levels, thereby suppressing appetite until weight loss occurs. Thus leptin regulates energy intake and fat stores so that weight is maintained within a relatively narrow range.
• Leptin also seems to play an important role in modulating the onset of puberty. For example, undernourished and thin girls take longer to reach puberty than normal girls. Thin girls often fail to ovulate or release an egg from an ovary during menstruation cycles. Reproductive growth and fat stores are, therefore, vital in the regulation of reproduction.
Besides many factors involved in the causation of obesity, an important factors is leptin resistance. Many believe that leptin resistance is the leading driver of fat gain in humans.
The main function of leptin is sending a signal to the brain, “telling” it how much fat is stored in the body’s fat cells. Since leptin is primarily produced by fat cells, obese people have very high levels of leptin. Given the way leptin is supposed to work, these people shouldn’t be eating because their brain should know that they have plenty of energy stored. But the problem is that the leptin signal is not working. As a result, there’s a whole lot of leptin floating around that the brain doesn’t “see” that it is there. This condition is known as leptin resistance. It is now believed to be the main biological abnormality in human obesity.
Therefore, leptin resistance makes the brain change our behavior in order to regain fat that the brain thinks is missing. The brain thinks that we must eat so that we don’t starve to death. Simultaneously, the brain also thinks we need to conserve energy, so it makes us feel lazier and thus makes us burn fewer calories at rest.
Losing weight reduces fat mass, which leads to a significant reduction in leptin levels. When leptin goes down, this leads to hunger, increased appetite, reduced motivation to exercise and decreased amount of calories burned at rest. Basically, the reduced leptin makes the brain think it is starving and so it initiates all sorts of powerful mechanisms to regain that lost body fat.
In other words, the brain actively defends the higher amount of fat mass by compelling us to eat back the lost weight. That is the main reason why yo-yo diets fail to yield the results as the dieters lose a significant amount of fat, only to gain it back.
How to regulate leptin hormone?
Though leptin resistance is a complex problem, it is not an irreversible one. The following factors will help improve leptin response:
• Reduce sugar and fructose consumption – Minimize using simple starches, refined foods, sugar and fructose. Fructose is a major contributor to insulin and leptin resistance. Fructose disrupts the signals of insulin and leptin, generally by over-taxing the liver because fructose is primarily shuttled to the liver for processing, whereas glucose is primarily shuttled to muscle and fat cells. By reducing the consumption of white sugar and high-fructose corn syrup, we allow liver to do other things like burning fat
• Optimize sleep – Try to be in bed by ten o’clock in the night. Take steps to optimize your sleep.
• Avoid frequent eating- When you are constantly eating, even small amounts during the day, it keeps your liver working and doesn’t give hormones a break. Try to space meals at least 3-4 hours apart and don’t eat for at least 3-4 hours before bed. This includes drinks with calories but herbal teas, water, coffee or tea without cream or sugar is fine.
• Exercise regularly- Your workout should include both aerobic exercise and strength training.
• Take more Omegs-3s – Take more Omega-3s by consuming fish, grass fed meats, chia seeds and minimize your Omega-6 consumption by consuming less of vegetable oils, conventional meats, grains, etc. to get lower inflammation and help support healthy leptin levels.
The bottom line
It is evidently clear that leptin – the satiety hormone – plays an equally important role in regulating hunger as is done by ghrelin. Recently, lot of importance has been attached to leptin resistance in humans, which is now considered to be the driving factor in causing overweight and obesity. There are many factors responsible for causing leptin resistance in humans. The majority of these factors are related to our lifestyle. Initiating positive changes in our lifestyle will help regulate the release of leptin hormone, thereby striking a balance between food intake and body weight.