What Is Leptin?
What is leptin? Well, it's probably the most important hormone that regulates your body weight, so keep reading...
For those of you who don't know, hormones are chemicals released by different cells in the body, and sent as signals to the brain (and not only), which subsequently makes adjustments according to its programming.
In this case, leptin is produced mainly in the fat cells, and it informs your body about its energy status. (Which makes perfectly sense because body fat is an accurate estimator of energy availability.)
For this reason, leptin correlates very accurately with body fat percentage, notably subcutaneous fat, and with a few exceptions more adipose tissue means more leptin in your blood stream.
As it turns out, the brain has many leptin receptors, especially the hypothalamus which controls appetite. So if you guessed that less leptin makes you feel hungry when dieting, you should congratulate yourself.
However, in the short term, this hormone is also influenced by your calorie/carbohydrate intake. According to your initial calorie deficit, leptin may decrease by half within one week although, of course, you haven't metamorphosed in a fitness model that fast.
Conversely, if you take a short diet break, leptin increases more than your body fat percentage – in fact, you may even continue to burn fat.
The details of this process are not important for Average Joe, but this has to do with changes in glucose metabolism in the fat cell.
In essence, the fat cells feel when calories are mobilized or stored, and this has an impact on leptin production and release.
In other words, this hormone is telling your brain not only how much body fat you have, but also how much you are eating (especially carbohydrates).
Therefore, your eating pattern influences leptin in the short term, and your girth size determines the long term changes.
Is important to note that the brain is much more sensitive to a decreasing trend of leptin, which from an evolutionary perspective makes perfectly sense because our bodies perceive weight loss as a survival danger.
Consequently, for most of us is much easier to gain weight rather than getting lean. (I'm sure you are in the same boat; otherwise, you wouldn't even bother to read this article.)
So my point is that your body doesn't mind if you are a fat ass, but it fights tenaciously if calories are reduced too much.
Knowing what is leptin and applying this information will help you to avoid the usual silly mistakes that most folks do when dieting. Bear in mind that this is not a trivial detail.
On a related note, besides having at least twice more leptin than men, women's leptin levels decrease far more drastically, and for this reason they are considered a different specie than men when it comes to weight loss.
Therefore, leptin's role is far from preventing obesity as it was originally thought. More precisely, this wicked hormone loves you so much that it doesn't want you to starve to death. So it tells quickly your body how and when to adapt in the face of a calorie deficit.
Now you have the big picture of what is leptin and its function. It's the anti-starvation hormone that signals your brain about the energy stores (both body fat levels and energy intake).
As mentioned, this hormone responds mostly to glucose, so eating fruits doesn't have much of an effect on it. Which means that once in a while, you can indulge yourself, and satisfy your natural cravings without feeling guilty whatsoever.
As a final note, leptin has far more functions than that, but these details are very boring and not relevant (unless you want to become an expert in endocrinology).
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