A method of screening for a candidate compound for the treatment of a condition involving dysregulation of metabolism in a mammal, by bringing a compound into contact with cells that express a GPCR and that further express a GRK, determining whether the contacting causes a response of the GRK in cells brought into contact with the compound, determining whether the contacting causes a response of a classical secondary messenger in cells brought into contact with the compound; and identifying the candidate compound based on the determined GRK response and response of a classical secondary messenger in the cells. A kit for use in the method. A compound for use in the treatment of a condition involving dysregulation of metabolism in a mammal and a method of treatment of such a condition.