Have we found a perfect weight loss treatment for humans? When we eat it's necessary to know when to stop eating. We have lot's of theories regarding to hunger control in the short run. Many of them associated with hypothalamus.
Leptin is a protein hormone secreted by the fat cells which acts as a signal to help our system to control the energy intake and energy expenditure especially in the long run. The amount of leptin in the blood has been directly linked to the amount of fat in the body.
Unfortunately leptin didn't become the instant cure for obesity. It appears that fatness doesn't occur because of low levels of leptin in the blood but because of the ineffectiveness of leptin. Similiar happens in type 2 diabetes with the insulin resistance.
How ever it is important to bear in mind that ascending leptin levels in people who have already lost some weight helps them to keep the weight off. It doesn't help people to lose weight in the first place but prevents the yo-yoing that most dieters come across as their leptin levels drop and the brain tries to compensate that by increasing hunger.