MEX3C deficiency impairs the development of white and brown adipose tissue. Hence the present invention provides, among other things, a method of screening a candidate compound for activity in inhibiting fat deposition in a subject in need thereof and/or treating a condition in a subject in need thereof, comprising: (a) contacting a candidate compound to a cell that expresses MEX3C protein and then (b) detecting a quantity of expression of the MEX3C protein in the cell a depression in the expression of MEX3C protein when the candidate compound is contacted thereto as compared to that expressed when the candidate compound is not contacted thereto indicating the compound is active in inhibiting fat deposition and/or treating a condition in a subject in need thereof. Methods of treatment and screening subjects are also described.