Leptin

Leptin is a very powerful and influential hormone made by fat cells that helps to: 

1-Regulate energy balance:
by inhibiting hunger thus regulating appetite through receptors in hypothalamus in the brain.

2-Regulation of fat stores is deemed to be the primary function of leptin.

This hormone that controls 100% of your body’s ability to burn fat  In short, lepttin is the way that your fat stores speak to your brain to let your brain know how much energy is available and, very importantly, what to do with.

Therefore, leptin may be on top of the food chain in metabolic importance and relevance to disease. High levels of Leptin speed up your metabolism and signal your body to burn fat and low levels of Leptin slow down your metabolism and signal your body to store fat.
Moreover, If your leptin signaling is working properly, when your fat stores are "full," this extra fat will cause a surge in your leptin level, which signals your brain to stop feeling hungry, to stop eating, to stop storing fat and to start burning some extra fat off.
Controlling hunger is a major (though not the only) way that leptin controls energy storage. 
Hunger is a very powerful, ancient, and deep-seated drive that, if stimulated long enough, will make you eat and store more energy.