In Portugal, sustainable eating behaviours tend to be adopted only occasionally. The average score is 2.92 on a scale from 1 (“Almost never” or “Never”) to 5 (“Almost always”). In contrast, the perception of the advantages of sustainable eating is high (4.15) and higher than the perception of the disadvantages (3.17), both measured on a scale from 1 (“Not at all important”) to 5 (“Extremely important”). These results show that, although adoption is not yet widespread, Portuguese adults clearly recognise more benefits than drawbacks associated with sustainable eating.

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Women adopt more sustainable behaviours and perceive more advantages than men, with no differences in the perception of disadvantages. Having children is associated with greater adoption of such behaviours and higher perception of the advantages. Higher levels of education are associated with greater adoption of sustainable behaviours but lower perception of the advantages and disadvantages. Doing one’s own shopping and engaging in physical activity are associated with greater adoption of sustainable behaviours and higher perception of the advantages, while engaging in physical activity is also associated with lower perception of the disadvantages.

A higher perception of the risk associated with climate change is linked to a higher perception of the advantages of sustainable eating, but does not directly lead to behavioural change. In contrast, self-efficacy for action emerges as one of the most consistent factors, being associated with greater adoption of sustainable eating behaviours, higher perception of their advantages, and lower perception of their disadvantages.

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Descriptive norms, that is, the perception that others adopt a sustainable diet, promote the adoption of such practices. In contrast, prescriptive norms, associated with social pressure to act, are related to lower adoption. Biospheric values, linked to concern about the environment, are associated with greater adoption of sustainable eating behaviours and higher perception of their advantages. Socio-altruistic values (related to the defence of social justice) are associated with a slight reduction in these behaviours, with no significant impact on the perception of their advantages or disadvantages. In turn, egoistic values, centred on personal interests, are mainly associated with higher perception of their disadvantages.

Food literacy refers to the knowledge, skills, and behaviours that enable individuals to make informed food choices. Domains of learning and nutritional, social, and industrial factors, as well as food policies, are associated with greater adoption of sustainable behaviours. In contrast, psychological, cultural, and health factors do not have a significant direct impact on the adoption of such behaviours. In general, higher levels of food literacy are associated with higher perception of the advantages of sustainable eating. However, the effects on the perception of disadvantages vary depending on the domains considered, reflecting the complexity of food-related decisions. These results highlight the multidimensional nature of food literacy.

The results of this study indicate that sustainable eating behaviours in Portugal are adopted on an occasional basis, although the population recognises more advantages than disadvantages. This difference suggests the existence of barriers that hinder the transition from intention to action.

Sociodemographic characteristics, individual beliefs, and sociocultural factors influence these behaviours. Self-efficacy for action, descriptive norms, and biospheric values stand out as factors that promote the adoption of sustainable practices. The perception of climate change risk, while relevant, is insufficient on its own to induce behavioural change.

Overall, the results show that promoting sustainable eating practices must go beyond environmental information and awareness-raising. Strategies are needed to strengthen people’s confidence in their ability to act, develop practical skills, and reduce perceived barriers, thereby facilitating the adoption of sustainable habits among the Portuguese population.

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