Understanding, assessing and modelling sustainable eating behaviours

Sustainable diets are aimed at promoting and supporting psycho-physical health and social well-being for actual and future generations by means of accessible, safe, healthy, environmental friendly, affordable, fair and acceptable food. Shifting dietary habits towards healthy and sustainable dietary patterns has been proved to represent a drive of change for more sustainable food systems, besides exerting beneficial effects on health outcomes and contributing to the mitigation of the climate change scenario. To drive this behavioural transition, tailored solutions need to be developed by applying strategies at multi-level involving different sectors within the food system and addressing the heterogeneity of social, demographic and economic background of the population. The complexity of dietary behaviours and the influence of a wide range of intrinsic and extrinsic determinants on dietary choices require a multidisciplinary approach addressing sensory, psychosocial, cognitive and environmental stimuli. Understanding consumer behaviour is crucial for developing strategies and interventions to foster the transition towards more sustainable diets at both individual and population level. In this framework, the application of psycho-social models to understand and predict sustainable eating behaviours is a valuable technique to design effective interventions. Based on these considerations, this Doctoral Thesis aims at providing recommendations for the development of effective intervention strategies addressed to improve the sustainability of dietary behaviours in childhood and adulthood. To pursue this objective, the first part of the thesis addressed the role of personal, social and environmental factors in explaining and predicting the adoption of a sustainable diet in the adult population, by applying a social-cognitive theoretical framework. The second part was focused on assessing the eating behaviour of primary school children, through the analysis of the sustainability outcomes of their school lunch plate waste in terms of nutritional, environmental and economic losses. First, a systematic review was carried out to identify the main drivers and barriers towards sustainable diets in adults by applying three psycho-social theories, i.e. the Theory of Reasoned Action (TRA), the Theory of Planned Behaviour (TPB), and the Social Cognitive Theory (SCT). The analysis of the reviewed studies showed a multitude of significant predictors of intention and behaviour. The most recurrent were attitude for intention and intention for behaviour. Thus, social-psychological models can be chosen for their validity in predicting dietary behaviours and in explaining behavioural change. However, they are more limited in explaining and predicting actual behaviour when prospective and more objective measures of food consumption are applied (e.g. food diaries and/or food frequency questionnaires). Subsequently, an online survey based on the TPB addressed to adults living in Italy was developed and proposed to a representative sample of Italian adults. The survey aimed at identifying the most relevant predictive variables explaining the intention to adopt a sustainable diet. Significant associations were found between the TPB constructs and the behaviour measures, underlining the main role of intention and perceived behavioural control in influencing human behaviour. The application of structural equation models revealed a high capacity of the TPB to explain both the intention to adopt the behaviour and the actual behaviour. In line with the literature, the explained variance of the behaviour was lower when a more objective measure was applied. In the final part of this Doctoral research, two Italian case studies were compared in relation to the impact of primary school children’s plate waste by assessing the embedded nutritional, environmental and economic losses. In both cases vegetables were the most wasted food group, followed by fruits and bread. Conversely, protein-based dishes, (semi)unique dishes containing both starchy-based and protein-based products dishes, and desserts were the least wasted. Overall, after adjusting for plate waste data, most of the lunch menus fell below the national energy and nutrient recommendations. The (semi)unique dishes, starchy food and protein-based dishes were found to be the most carbon emissive food categories. Moreover, a significant quota of the total waste CO2 burden was ascribable to the agricultural and processing phases, these being the most emissive steps along the school meal supply chain. The different food composition of plate waste of the two case studies affected not only the relative carbon emission burden, but also the associated economic cost and the cost per meal. A relevant share of the entire budget for food procurement was spent on food that was discarded by children. In conclusion, by identifying the drivers of consumers’ behaviour and the associated beliefs, the findings of the TPB study may support policy makers in recommending and defining primary prevention interventions for enhancing consumer awareness and engagement towards more sustainable dietary habits. In particular, based on the obtained results, interventions targeting the adult population in Italy should be addressed at improving their attitude and perceived control over the behaviour. Providing more information on the product labels, increasing the food variety in collective catering, and reducing the price of sustainable food products are strategic measures recommended to achieve this objective. On the other hand, important recommendations to minimise the discarded food may emerge from the children’s plate waste study, i.e. supporting food educational programs in primary schools, defining school governance for healthy and sustainable eating habits, addressing teachers’ attitude during the school lunch and school catering management in serving lunch menus, monitoring children’s plate waste over time, and finally rethinking national guidelines for standard portions