Current empirical observations largely suggest a body downsizing in response to harvesting, associated with population declines and decreased harvesting yields. These changes are often construed as direct consequences of harvest selection, where smaller-bodied, early reproducing individuals are immediately favoured. Harvesting and evolution of body size however alter many ecological aspects, affecting for instance competitive and trophic interactions. Such changes reshape the fitness landscape thereby altering the subsequent evolution of body size. Predicting these changes in fitness landscapes, and from there the productivity and dynamics of harvested populations, requires accounting for a constant interplay between ecological and evolutionary changes termed eco-evolutionary feedback loops (EEFLs). We analyze scenarios under which EEFLs acting at the population or community levels either oppose or magnify harvest-induced body downsizing. Opposing EEFLs favour body-size stasis but erode genetic variability and associated body-size evolvability, and may ultimately impair population persistence. In contrast, synergistic EEFLs initially favour population persistence and preserve body-size evolvability, but drive fast evolution towards smaller body sizes and increase the probability for trophic feedbacks that may ultimately lead to population collapse. EEFLs imply that reduced ecological effects of harvesting also produce smaller evolutionary changes, and thus pave the way towards a convergence of the ecological and evolutionary perspectives on harvest management. We advocate for a better consideration of natural selection which effects, we believe, should be integrated among default a priori assumption in studies of harvested populations.