The hormone Leptin, some will call it the obesity hormone or starvation hormone. It was first discovered, not so long ago, in 1994 by scientists and raised huge excitement among the "losing weight" and dieter’s community.

Some scientists would call Leptin the Starvation hormone and not the obesity hormone. The hormone Leptin is produced in our fat cells goes to the brain through our bloodstream. Thanks to the Leptin, our fat cells are able tell the brain that our energy levels are just as right. Each person has a Leptin "Threshold" that is apparently set when we are born.

When your leptin level is above that threshold, fat cells are telling to the brain that they have enough energy to function normally, so that includes doing work out in a normal rate, burning energy in a normal speed and eat food in a normal amount.

So what happens when people go on a diet?

Let’s say you reduce your food amounts, or starve yourself and you start losing weight. Then your leptin levels are going down, below the threshold. Then the fat cells tell your brain: "Hey, we don’t have enough energy down here, will you do something?" this is causing the brain to get into starvation mode. Now your body feels that it needs to get this energy back to your fat cells, to generate more leptin and to get back to that threshold. This is what causing you to eat and what makes your leptin level get back to where it was.

So let’s simplify things. When Leptin levels are low, you are hungry. When they are high you feel full. So you might think to yourself now: "So why should not I take this Leptin thing as a pill or something, to "feel full", and this way I would lose weight? "Wrong!

Well that was the first thing that people hoped when they first discovered Leptin in 1994. Finally there was a clear proof that obesity has a physiological explanation and it’s not just people who are being fat.

The obesity community was at a thrill. Many doctors believed that if you would give Leptin to people, that would raise the levels of Leptin and that would signal the brain to stop eating. But experiments showed that when people took it, it did not work so well.

You see, Leptin is made in the fat cells, so the more you are fat the more Leptin you make. That was a surprise to everyone because all thought that they are going to find low levels of Leptin in obese people. You see, the problem is deeper than that. In fat people, it is not the amount of leptin in the fat cell. It is just the Leptin is trying to signal to the brain to stop eating, but the brain will not get it. Something in this communication is not working right. This is called Leptin resistant, and the more you have it, the fatter you will be.

So basically it makes no sense to give Leptin to Leptin resistant people. It does not matter how much you give, it will not overcome this resistant.

Leptin works only in extremely rare cases in when people does not produce Leptin at all and become obese. When getting Leptin through injection this tiny group of people will stop overeating and lose weight. But for the majority of people it will not work. Leptin was never approved to be a treatment for weight loss.