Knowledge, Perceived Importance, Current Uptake, and Willingness to Adopt Healthy Sustainable Dietary Actions: A Cross-Sectional Study of UK Adults

<b>Background/Objectives</b>: Sustainable diets are essential for public health, food system resilience, and environmental protection, yet engagement with healthy sustainable dietary actions is varied. This study investigated knowledge, perceived importance, current uptake, and willingness to adopt healthy sustainable dietary actions among the general UK population. <b>Methods</b>: A cross-sectional study was conducted using a self-report questionnaire completed by 635 adults (205 males and 430 females; mean (SD) age = 43 (16.8) years) in the UK. <b>Results</b>: Considerable variation in knowledge, perceived importance, and current engagement was found across the dietary actions investigated. All three were highest for familiar, health-aligned behaviours, while actions with a stronger environmental focus that were less conventional or culturally unfamiliar were less well understood, perceived as less important, and less often engaged with. Willingness to adopt actions not currently practised was most strongly predicted by perceived importance (smallest β = 1.21, <i>p</i> < 0.001), with perceived value also significant for several actions (smallest β = 0.86, <i>p</i> < 0.001). Knowledge and perceived impact were generally non-significant. Demographic and lifestyle factors showed smaller effects, with greater willingness among younger individuals (smallest β = -0.24, <i>p</i> = 0.01) and those with higher education (smallest β = 0.51, <i>p</i> = 0.01). <b>Conclusions</b>: These findings suggest some knowledge and engagement with healthy sustainable dietary actions in the UK. However, future campaigns may need to go beyond awareness-raising to emphasise the personal significance and value of these actions. These cognitive factors also showed broad applicability across demographic and lifestyle variables, suggesting potential for widely effective interventions.