A study led by a scientific team at Beth Israel Deaconess Medical Center (BIDMC) provides another important step in our understanding of the critical role that the brain’s molecular pathways play in the development of obesity and related disorders. The findings, reported in the November 4, 2005 issue of the journal Cell, demonstrate for the first time that the neuronal pathways that help to keep body weight stable diverge at the melanocortin-4 receptor (MC4R) to regulate either food intake or energy expenditure. This unexpected discovery helps to extend the understanding of the complex neurocircuitry behind body weight control, an endeavor that began more than a decade ago with the identification of the leptin hormone and which has been growing steadily ever since.