<p>Even when the gut is rich in nutrients, microorganisms can experience nutrient deprivation owing to factors such as fluctuations in host feeding patterns, microbial competition and selective nutrient uptake by the host. Nutrient starvation affects microbial survival, microbiome dynamics and intestinal stability, yet remains underexplored. This Perspective explains how nutrient deprivation shapes microbial physiology, ecology and evolution to drive complex interactions both among microbial species and between microorganisms and their host. We discuss host lifestyles that can result in microbial starvation, including diet shifts, fasting and hibernation. We also highlight critical gaps in our understanding of how starvation affects microbial community assembly, stress responses and cross-feeding from lysed cells, with implications for chronic infections and therapeutic strategies. We outline technological developments needed to unravel microbial survival strategies under nutrient deprivation. Understanding how starvation in all its forms shapes the gut ecosystem will be important to ultimately advance microbiome engineering and health interventions.</p>