The function and properties of leptin have been discussed extensively and few people have thoroughly examined its exact relation to our body and the mechanisms it employs. So what is leptin? Leptin is an adipokine released by adipocytes; in a simple language, a hormone produced by fat cells. It decreases food consumption, stimulates the process of thermogenesis, improves lipid oxidation and increases insulin sensitivity in cells in the peripheral organs.
Besides monitoring and controlling the long-term balance of energy, it has the potential to affect the activity of neurons. It’s a messenger that goes to your brain and practically notifies it that the current energy levels are sufficient to do the daily essential metabolic functions. Basically, the brain comes to a conclusion that you can expend energy at a normal pace and not feel tired or drained out.
The Mechanism Behind Leptin ?
Let’s observe what happens in your body when leptin go down. If the leptin levels are reduced, the brain will look at this as if you were in a situation where you are starving. What happens is that if the brain doesn’t get the “message” from leptin that there’s enough energy, the brain will start thinking that you are starving making you go into “couch potato” mode, so that it can prevent you from burning any additional reserves of energy.
The brain will get “scared” thinking “I shouldn’t waste energy needlessly and need to preserve as much as possible since I don’t know when’s the next time we’ll find food”. The body will react by suppressing the metabolism in order to conserve calories as much as possible. This is a natural occurrence in pregnant women and during puberty. This may sound odd at first and you might be wondering what is it that connects these two conditions. Well, looking from another perspective, if leptin were always active, it’d be really difficult to gain any amount of weight.
Weight gain and weight loss
If women couldn’t gain weight during pregnancy, we wouldn’t have been able to survive as a species. Looking at it from the point of Darwin’s theory of evolution and “survival of the fittest” if we can’t gain weight and preserve energy we won’t be “fit” to survive and propagate our genes which would lead to the extinction of our genes.
And what happens with those who still haven’t gone through puberty or those who passed it? What about those who aren’t pregnant? Why do they experience it too? The thing is that leptin signals to the hypothalamus that there’s enough energy left to burn. If the hypothalamus gets the message from leptin, the body enter a state of anorexigenesis, which is basically appetite loss. This basically means that the brain gets the message that it isn’t hungry and that it has the permission to use fat deposits as an energy source.
The aforementioned process triggers the sympathetic nervous system resulting in a surge of energy which will cause the fat cells to release the stored fat. Additionally, anorexigenesis notifies the vagus nerve, also called the energy storing nerve to cease insulin release since the body isn’t hungry. If in this instance, the hypothalamus doesn’t get the leptin message, the body gets into a state of orexigenesis, which means gaining an appetite.
This, in turn, means that the brain will get the message that the body is starving and tell it to preserve energy. This causes the sympathetic nervous system to turn off, so to speak. When this happens, the vagus nerve “turns on”. Then, the brain thinks that the body is hungry and needs more leptin. When it needs leptin, the body releases a bigger amount of insulin.
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