Leptin is a hormone produced by fat cells. This hormone, also known as the "satisfaction hormone", reduces your appetite and makes you feel fuller. It is a type of signal hormone that your brain sends to your body to stop eating and keep your stomach full. This convinces the body that it has stored enough fat and should not avoid overeating. To know more please check - How To Increase Leptin And Decrease Ghrelin.
Obese or overweight people tend to have higher levels of leptin in their blood. One study even went as far as possible and found that leptin levels in overweight people are about four times higher than those in normal-weight people.