According to Rober H. Lutig, professor of pediatrics and member of the Society of Endocrinology Obesity Task Force: "It is not our hormone of obesity, it is our hormone of hunger." It is a protein that is made in fat cells, circulates in the bloodstream, and goes to the brain. "It is the way your fat cells tell your brain that your power thermostat is fine." "It tells your brain that it has enough energy stored in its fat cells to participate in relatively expensive and normal metabolic processes," he says. In other words, when your leptin level is above the set threshold, your brain detects that you have enough energy, which means you can burn energy at a normal rate, eat food in a normal amount, exercise at a normal rate "