Specific dynamic action (SDA) describes the rise in metabolic rate following feeding and has been documented in animals for more than a century. SDA is commonly referred to as the energetic cost of digestion. In practice, however, the response is far less convenient. The postprandial increase in metabolism integrates processes that extend well beyond digestion, including nutrient absorption, protein synthesis, ion regulation, and the metabolic reorganisation that follows nutrient assimilation. This complexity has fuelled a long-standing debate about the physiological processes that drive SDA. In 2024, I published a commentary in the Journal of Experimental Biology challenging the prevailing assumption that SDA primarily reflects the energetic cost of digestion. Since then, researchers have begun testing these hypotheses, and emerging evidence suggests that a substantial proportion of SDA arises from post absorptive processes, particularly protein turnover and tissue synthesis, rather than the mechanical or secretory costs of digestion alone. This reframing has important implications for how we interpret feeding energetics, growth efficiency, and the physiological constraints imposed by environmental stress. In this talk, I use my research on SDA as a lens through which to revisit the history of this response, interrogate how it is currently interpreted, and explore where a more mechanistic framework may take the field.