Organisms' survival hinges on their food intake, which influences growth, maintenance, and reproduction by providing essential macronutrients. However, an optimal macronutrient mix that maximizes an organism's evolutionary fitness isn't always accessible, leading to dietary discrepancies that can affect performance. To delve deeper into these dietary consequences, we studied how macronutrient composition impacts specific organismal traits and gene expression. We employed Drosophila melanogaster—a suitable model for such dietary evaluations—to assess the effects of isocaloric diets differing in protein-to-carbohydrate ratios on eight critical life-history attributes in a substantial outbred population (n≈2,500). Results showed that reducing carbohydrates in an isocaloric diet sped up pre-adult development and enhanced reproduction, without altering pre-adult viability or body size. However, higher carbohydrate levels curtailed lifespan, as indicated by faster aging, evidenced by reduced locomotion and deteriorating gut health. Additionally, gene expression showed noticeable plasticity based on diet: high-carbohydrate diets primarily increased gene activation, while protein-rich diets leaned towards suppression. Our study illuminates how macronutrient mix shapes life history characteristics and their connections, providing valuable perspectives on the possible adaptive mechanisms organisms might employ in response to consistent dietary challenges in our rapidly changing environment.
Impact of Isocaloric Dietary Manipulation on Life-History Traits and Gene Expression in Outbred Drosophila melanogaster Population