Produced by fat cells, leptin is a protein that affects receptors in the hypothalamus of the brain. One of the primary functions of the substance appears to be the regulation of appetite and food consumption. The biochemical is believed to carry out this function by counteracting the effects of two potent feeding stimulants known as neuropeptide Y and anandamide, as well as promoting the activity of alpha-MSH, an appetite suppressant. A tremendous amount of leptin research is currently in progress, especially among scientists seeking for new ways to combat the growing problem of obesity. Thus far it has been discovered that the amount of leptin in the body is highly correlated to the amount of fat it contains, and some researchers believe that the great concentrations of leptin in many obese people may be an indication that they have a reduced sensitivity to the substance.