Direct comparison of Drosophila food intake assays. Sonali A Deshpande, Ariadna Amador, Sany Hoxha, Angela M Phillips, William W Ja. Department of Metabolism and Aging, The Scripps Research Institute, Jupiter, FL.

   Metabolic diseases like type-2 diabetes and obesity are associated with disorders in food consumption. Although Drosophila is widely used as a model organism to study feeding and metabolic disease, assays to accurately measure food consumption remain poorly characterized. Due to the difficulty in measuring small volumes consumed by flies, existing food intake assays are argued to be unreliable, imprecise and inaccurate. Poor food intake measurements can result in erroneous interpretations of studies in metabolism, nutrition, behavior, and disease. Here, we compare four popular food intake assays: the Capillary Feeder (CAFE), food-labeling with a radioactive tracer or a colorimetric dye, and observations of proboscis extension. We measure the resolving power of each technique under typical experimental conditions and directly compare them by performing combinations of assays simultaneously on the same cohort. While each approach has distinct advantages, we show that the CAFE and radio-labeling assays stand out by resolving differences in feeding that dye-labeling and behavioral measurements fail to distinguish. Understanding the strengths and limitations of the various food intake assays greatly facilitates all studies where feeding behavior plays an important role.