Multiple factors interact to determine the lifespan of an organism. The Promislow lab uses the fruit fly Drosophila melanogaster to study the interaction between the metabolome (the profile of all small molecules within an organism), and the lifespan of a fly under stress. In a study of metabolome and lifespan data for many genotypes of Drosophila, our lab found that fly strains with relatively long lifespans when exposed to oxidative stress (peroxide food), had high levels of maltose, a disaccharide of glucose. We hypothesized that maltose was beneficial to flies on peroxide food, and tested this by supplementing the diet with maltose to see if this would extend lifespan. Flies fed supplemental maltose prior to exposure to peroxide food lived longer than flies fed unsupplemented food, supporting our hypothesis. Maltose could extend lifespan by providing energy to the fly via metabolism into glucose, or through another function as a disaccharide. To distinguish between these possibilities, we tested lactose, a disaccharide, to determine if any disaccharide could extend lifespan. Lactose did not extend lifespan, suggesting that disaccharides in general do not extend lifespan under stress. We found that glucose extended lifespan, supporting the hypothesis that maltose extends lifespan via conversion to glucose. Maltose can be stored as glycogen, a polysaccharide, and glucose is derived from glycogen by glycogen phosphorylase, encoded by the gene GlyP. To test the role of glycogen metabolism on lifespan under stress, we manipulated the expression of GlyP. Several transgenes were used to reduce the expression of GlyP by RNA interference (RNAi). RNAi of GlyP decreased lifespan, which supports our hypothesis that glucose derived from glycogen promotes survival. Our work suggests that glucose derived from glycogen or maltose is an important determinant of lifespan under stress, furthering our understanding of links between metabolism and complex phenotypes, like lifespan.