Many experimental approaches are available to quantify fat content in Drosophila , but, for the purposes of efficient screening of large numbers of animals and focusing on the stage of development concerned with food consumption and energy storage-the wandering third-instar larva-a density-based approach maximizes time and cost effectiveness and allows for downstream analysis by other methods. Solutions of varying concentrations of sucrose are used to reveal differences in the density of individual larvae, which correlate with body fat content across a wide range of genetic backgrounds. When coupled with appropriate attention to developmental timing and the use of appropriate controls for the effects of genetic background, analysis of body fat by this method is rapid, robust, reproducible, and noninvasive.