Animals must carefully budget their energy expenditure to fuel various biological processes: biomolecule synthesis, cell division and gamete production must all be fuelled from an animal's limited energy reserve. Organisms that eat microplastics display reductions in these parameters, which suggests that microplastics alter the amount of energy animals allocate to these important processes. The Dynamic Energy Budget model can help researchers identify how animals that eat microplastics alter the amounts of energy they allocate to biological processes. The model outlines how energy is allocated amongst competing biological processes, and so it can be used to identify which energy pathways are affected by microplastics. In turn, this can assist researchers to identify the mechanisms behind organism-level responses to plastics ingestion – a vital step in progressing our understanding of how micro- and nanoplastics affect animals. Despite the utility offered by the Dynamic Energy Budget model – and that fact that it has been successfully used in other biolgical fields – the model remains largely unknown amongst microplastics researchers. Here, we highlight how the Dynamic Energy Budget model can contribute to a mechanistic understanding of micro- and nanoplastics effects in animals. This presentation will: Use the Dynamic Energy Budget model to explain how organisms allocate energy to biological processes, like growth and reproduction. Demonstrate how to use the Dynamic Energy Budget model to identify biological pathways that are affected by micro- and nanoplastics. Outline which endpoints researchers should measure to adopt the Dynamic Energy Budget model in their studies.