The Psychosocial Antecedents of the Adherence to the Mediterranean Diet

From motivation to mediterranean diet intention and behavior: a combined self-determination theory and theory of planned behavior approach

OBJECTIVE

The Mediterranean diet (MD) is recognized as one of the healthiest and most sustainable dietary patterns worldwide. This study combines the Theory of Planned Behavior (TPB) and Self-Determination Theory (SDT) alongside past MD adherence behavior to predict MD adherence among young and adult Italians.

METHODS AND MEASURES

Using a two-wave prospective design, 706 participants (Women = 60.5%, mean age = 31.82) completed measures of past behavior, SDT and TPB variables at baseline (T1) and reported their adherence behavior to MD two weeks later (T2).

RESULTS

Results revealed that both intention and past adherence to MD predicted actual adherence. In turn, affective attitude, descriptive norm, perceived behavioral control (PBC), and autonomous motivation were positively associated with intention. Past adherence further predicted autonomous motivation, affective attitude, and PBC, and indirectly influenced MD adherence at T2 through its effect on these factors and intention. Finally, invariance tests showed no differences between women and men and between student and non-student samples.

CONCLUSION

Overall, our findings support the integration of TPB and SDT, emphasizing the need for interventions that address both conscious decision-making and established dietary habits, acknowledging the multifaceted nature of dietary behavior change.

Synthesizing comprehensive models for health behavior studies: connecting dots and revealing links on health enhancement through a meta-analysis approach

Objective

To systematically synthesize the impact of autonomy and key theoretical models, including Self-Determination Theory (SDT), Technology Acceptance Model (TAM), Value Adoption Model (VAM), Theory of Planned Behavior (TPB), and Health Action Process Approach (HAPA), on health behavior and behavior change determinants, focusing on self-determination and intrinsic motivation as central drivers of independent health decisions.

Methods

A meta-analysis was conducted on 135 studies published between 2005 and 2023, with a total sample size of 53,242 participants. We searched the Web of Science and PubMed databases for relevant literature. The theoretical frameworks explored include SDT, TAM, VAM, TPB, and HAPA. Data analysis was performed using Review Manager 5.4.1 software, with effect size calculated as the standardized mean difference with 95% confidence intervals. Heterogeneity was evaluated using I2 statistics.

Results

(1) SDT significantly impacted motivation, while TAM and VAM influenced perceived value [SMD = 0.96 > 0.8, 95% CI (0.68, 1.24), P < 0.001]. (2) Implementation intentions, action planning, and coping planning were key moderators of health behavior change (I2 = 65.4%). (3) HAPA's structured planning strategies positively impacted long-term health behavior changes.

Conclusion

Autonomy, self-determination, and intrinsic motivation play a crucial role in health behavior change. Integrating theoretical models such as SDT, TAM, VAM, and HAPA facilitates structured approaches to health interventions, emphasizing implementation intentions, action planning, and coping strategies.

Drivers and Barriers Influencing Adherence to the Mediterranean Diet: A Comparative Study across Five Countries

Given the global decline in adherence to the Mediterranean Diet (MD), even within its native region, it is key to identify the factors influencing this trend to mitigate the negative health outcomes associated with westernized diets. To this end, 4025 individuals (49.6% women, 42.6 ± 14.2 y/o) from Greece, Italy, Morocco, Slovenia, and Tunisia remotely completed a series of measures assessing motives, attitudes, and psychosocial factors related to MD adherence, which was evaluated using the MEDAS questionnaire. The results suggested medium-to-low adherence across all countries, with the highest adherence in Italy and Morocco and the lowest in Slovenia. Structural equation modeling revealed that positive attitudes toward the healthiness of food were the strongest predictors of adherence, whereas picky eating was a significant negative predictor in all countries except Greece. Adherence to the MD was positively influenced by health motivations in Morocco and weight control in Slovenia and Greece, while sensory appeal negatively influenced adherence in Italy. Additionally, price and convenience were significant barriers in Tunisia and Greece, whereas a preference for local and seasonal foods promoted adherence in Morocco and Greece. Overall, our findings underscore the need for country-specific interventions and policies that address distinct local factors and motivations to ease favorable shifts in dietary patterns toward MD principles.

Integrating the theory of planned behavior and the self-determination theory to promote Mediterranean diet adherence: A randomized controlled trial

The Mediterranean diet (MD) is one of the healthiest and most sustainable food regimes. Nevertheless, MD diffusion is still limited, emphasizing the need to understand the psychosocial factors that could predict and promote its adoption. Starting from an integrated model of Theory of Planned Behavior (TPB) and Self-Determination Theory (SDT), the present randomized controlled trial investigated the effect of manipulating motivation (autonomous vs. controlled) on intention and MD adherence behavior. Participants included 726 Italian adults randomly allocated to one of three conditions: autonomous motivation manipulation, controlled motivation manipulation, and control group. TPB variables were measured immediately after manipulation (T1), while MD adherence was evaluated 2 weeks later (T2). Results from multivariate analyses of variance highlighted that participants in the autonomous motivation condition reported higher intention and a more favorable cognitive attitude than control group participants. However, no change in behavior was found. Moreover, a path analysis with mediation effect showed that the impact of autonomous motivation condition versus control group on intention was mediated by cognitive attitude. Findings support the integration of TPB and SDT to encourage intention to adhere to the MD, also suggesting that prompting autonomous motivation may help to promote a greater diffusion of this healthy and sustainable dietary pattern.

Psychosocial drivers influencing local food purchasing: beyond availability, the importance of trust in farmers

Introduction

Although consumers bought more local food during the changing context of pandemic COVID -19, this positive modification may not become a stable habit afterward.

Methods

To understand this change in drivers of consumers' intention to buy local food, we investigated the role of perceptions of various intrinsic and extrinsic attributes of local food, its perceived quality, price and availability, and consumers' trust in local food producers. We also investigated the role of sociodemographic variables as well as the moderating role of consumers' stage of change (i.e., absence, reduction, maintenance, and increase) in the purchase of local food.

Results

Structural equation modeling results on a representative sample of Italian consumers (N = 511) showed that local food availability is the main driver of purchase intention (β = 0.20; p = 0.001), especially among consumers who have changed their habits toward buying local food (reduction stage = β = 0.24; increase stage = 0.30; p = 0.001). In addition, trust in local food producers was found to be a key antecedent to consumers' perceptions of local food as environmentally friendly (β = 0.57; p = 0.001), healthy (β = 0.55; p = 0.001), authentic (β = 0.58; p = 0.001), tasty (β = 0.52; p = 0.001), socially sustainable (β = 0.59; p = 0.001), and as a product with a good appearance (β = 0.55; p = 0.001).

Discussion

Overall, these results improve our understanding of which food attributes should be emphasized in communication to promote the purchase of local food.

Predicting the Adoption of a Sustainable Diet in Adults: A Cross-Sectional Study in Italy

Shifting food choices towards sustainability entails the analysis of dietary behavior determinants. This study aimed to explain and predict the intention to follow a sustainable diet and its adoption in a representative sample of adults (n = 838) in Italy. An online survey based on the theory of planned behavior (TPB) was developed. The adoption of a sustainable diet was measured as self-perceived behavior, adherence to the Mediterranean diet (MD), and food consumption frequencies. Psychometric analysis and correlations between attitude, subjective norms, and perceived behavioral control (PBC) with both intention and behavior assessments were evaluated. Structural equation models were used to test whether and to what extent attitude, subjective norms, and PBC explained intention and behavior. Significant associations were found between TPB constructs and the behavior measures underlining the main role of intention and PBC in affecting behavior. The applied TPB models explained behavioral intention at most (78%). The results suggested promising interventions in narrowing the attitude-behavior gap to encourage specific adult population groups in Italy to adopt virtuous food consumption habits. Beside the implementation of price mechanism strategies, educational initiatives to increase awareness about food and diet sustainability issues and the reinforcement of the perceived control on food consumption at the individual level are recommended.

"I Always Buy the Purple Ones … If I See Them": Socioecological Factors Influencing Anthocyanin-Rich Food Consumption for Cognitive Health in Older Adults

Despite the positive relationship between anthocyanin-rich foods and cognitive health, a dietary deficit exists in older adults. Effective interventions require an understanding of people's dietary behaviors situated in social and cultural contexts. Therefore, the aim of this study was to explore older adults' perceptions about increasing their consumption of anthocyanin-rich foods for cognitive health. Following an educational session and the provision of a recipe and information book, an online survey and focus groups with Australian adults aged 65 years or older (n = 20) explored the barriers and enablers towards eating more anthocyanin-rich foods and potential strategies to achieve dietary change. An iterative, qualitative analysis identified the themes and classified the barriers, enablers and strategies onto the Social-Ecological model levels of influence (individual, interpersonal, community, society). Enabling factors included a desire to eat healthily, taste preference and familiarity of anthocyanin-rich foods (individual), social support (community), and the availability of some anthocyanin-rich foods (society). The barriers included budget, dietary preferences and motivation (individual), household influences (interpersonal), limited availability and access to some anthocyanin-rich foods (community) and the cost and the seasonal variability (society). The strategies included increasing individual-level knowledge, skills, and confidence in utilizing anthocyanin-rich foods, educational initiatives about the potential cognitive benefits, and advocating to increase access to anthocyanin-rich foods in the food supply. This study provides for the first time, insight into the various levels of influence impacting older adults' ability to consume an anthocyanin-rich diet for cognitive health. Future interventions should be tailored to reflect the barriers and enablers and to provide targeted education about anthocyanin-rich foods.

Affective components in promoting physical activity: A randomized controlled trial of message framing

Although the study of the affective components involved in predicting physical activity is spreading faster and faster, there is a lack of studies testing their role when promoting physical activity through message interventions. In the present study, we considered these components by focusing on how anticipated affective reactions and emotional processing of the messages influence receivers’ affective attitude toward physical activity, concurrent behavior, and future intention. A sample of 250 participants was involved in an intervention relying on prefactual (i.e., “If … then…”) messages promoting physical activity. All messages were sent through a research app and were focused on the expected consequences of exercising (or not exercising). Four experimental conditions involving messages differing as to their outcome sensitivity framing (i.e., gain, non-loss, non-gain, and loss) were compared to a control condition. Results showed that reading gain and non-gain messages enhanced the positive affective attitude toward physical activity, compared to control. Enhanced affective attitude after the intervention increased, in turn, self-reported physical activity and future intention. Interestingly, gain messages were even more persuasive for people with a low level of positive anticipated affective reactions. Furthermore, their effectiveness was especially attributable to the elicitation of hope in receivers. Discussion focuses on the advantages of considering affective components and their implications when promoting physical activity.

The Effect of Message Framing in Promoting the Mediterranean Diet: The Moderating Role of Eating Self-Efficacy

Although a Mediterranean diet (MeDiet) provides several psychophysical health benefits, research on how to effectively promote MeDiet adherence is still lacking. In the present study, we tested the effectiveness of a messaging intervention aimed at promoting the adherence to the Mediterranean diet. A total of 435 Italian participants responded to a questionnaire on their eating self-efficacy and adherence to the MeDiet at Time 1. Then, participants were randomly assigned to three different conditions: (a) gain messages focused on the positive outcomes of MeDiet adherence; (b) non-loss messages focused on the avoided negative outcomes associated with MeDiet adherence; (c) no messages (control). After the 2 week intervention, participants answered some questions regarding their perception of threat and distress, evaluation of the messages, and adherence to the MeDiet at Time 2. We also tested whether the messaging intervention influenced participants' MeDiet adherence at Time 2. Results confirmed that the messaging intervention enhanced the MeDiet adherence (F(2,432) = 4.61; p = 0.01, ηp² = 0.02), with no difference between exposure to gain or non-loss messages (95% LLCI = -0.32; 95% ULCI = 0.54). We then tested whether message framing effectiveness was influenced by eating self-efficacy, and results showed that gain messages were more persuasive for participants with low eating self-efficacy (effect size = 0.01; p for interaction = 0.03). Discussion suggests that tailoring messages according to receivers' psychological characteristics seems to be pivotal to enhance the persuasiveness of messages aimed at promoting the MeDiet adherence.