Front-of-pack nutrition labels (FoPLs) have been adopted in many countries to help consumers rapidly assess the nutritional quality of foods and to encourage healthier choices. Among these schemes, interpretive systems such as Nutri-Score appear particularly promising, as their graphic design improves understanding and use compared with more complex or purely numerical formats. In France, where social inequalities in diet-related chronic diseases are pronounced, implementing and effectively using FoPLs is especially challenging in socioeconomically vulnerable areas. Seine-Saint-Denis, a department with a markedly higher prevalence of diabetes and cardiovascular diseases than the national average, offers a relevant setting to test prevention strategies embedded within routine care. The PEANUTS project is a quasi-experimental before-after interventional study conducted in primary care and hospital outpatient settings, with later extension to the social sector. It aims to evaluate the effectiveness of a brief, literacy-sensitive nutrition education program focused on on-pack nutrition information (Nutri-Score, nutrition facts panel, claims and marketing elements) on self-efficacy, food literacy and the nutritional quality of purchase intentions among adults living in vulnerable territories.

Front-of-pack nutrition labels (FoPLs) have been adopted in many countries to help consumers rapidly assess the nutritional quality of foods and to encourage healthier choices. Among these schemes, interpretive systems such as Nutri-Score appear particularly promising, as their graphic design improves understanding and use compared with more complex or purely numerical formats. In France, where social inequalities in diet-related chronic diseases are pronounced, implementing and effectively using FoPLs is especially challenging in socioeconomically vulnerable areas. Seine-Saint-Denis, a department with a markedly higher prevalence of diabetes and cardiovascular diseases than the national average, offers a relevant setting to test prevention strategies embedded within routine care.

The PEANUTS project is a quasi-experimental before-after interventional study conducted first in primary care and hospital outpatient settings, with subsequent extension to social and community-based structures. The study targets adult patients living in vulnerable territories who attend municipal primary care centres or hospital services. After informed consent, participants complete a baseline questionnaire assessing food literacy, understanding and use of on-pack nutrition information (including Nutri-Score), perceived self-efficacy in choosing healthier food products in the supermarket, and the nutritional quality of purchase intentions.

The intervention consists of a brief (45-60 minute) group-based education session focused on on-pack nutrition information (Nutri-Score, nutritional declaration, nutrition and health claims, and key marketing elements). Sessions are modular and literacy-sensitive: based on the inclusion questionnaire, participants are allocated to educational pathways (Group A and/or Group B) according to their initial knowledge and food literacy profile, with two levels of intensity in each pathway (A1/A2 and B1/B2). At the beginning of each session, facilitators perform a short educational assessment to select the most appropriate level for the group and adapt examples and activities to participants' literacy levels and everyday food purchasing context. All sessions include an active discussion phase followed by a practical "learning by doing" component, using real or mock food packages and price scenarios to support the use of Nutri-Score and other FoPL elements in constrained-budget situations.

In Phase 1, the program is implemented in a university hospital group and municipal health centres in Seine-Saint-Denis. Interventions are delivered by advanced practice nurses and dietitians trained in the study protocol. Approximately 100 participants will be included in this phase, allowing an initial evaluation of feasibility, acceptability and preliminary effectiveness, as well as the collection of qualitative feedback (e.g. spontaneously raised questions, strategies to handle group heterogeneity) to inform training materials for non-specialist facilitators. In Phase 2, the program is transferred to social services and community-based organizations, where social workers and volunteers trained in PEANUTS will deliver the same modular intervention, thereby supporting capacity-building in the social sector.

Outcomes are measured at inclusion, immediately before the intervention (T0), immediately after the session (T1) and at 1-month follow-up (T2). Primary outcomes include self-efficacy in choosing healthier food products in the supermarket and a multidimensional food literacy score (label reading and food selection, meal planning and budgeting, food safety/preparation/cooking). Secondary outcomes include changes in the nutritional quality of food purchase intentions and participants' understanding and perceived usefulness of on-pack nutrition information. By integrating a brief, tailored education program into routine care pathways and later into social and community settings, the PEANUTS study aims to provide transferable tools to reduce nutrition-related health inequalities in vulnerable territories.

Inclusion Criteria:

• Respondents must be aged 18
• No formal income criterion is applied; Participants are considered as low-income (justified by the fact that the study is conducted in an area known to be socioeconomically vulnerable).

Exclusion Criteria:

• Subjects who are homeless
• Subjects who depend exclusively on food aid (Subjects never engaging in grocery shopping)
• Subjects living outside of mainland France
• French language comprehension will be assessed at baseline using functional health literacy questions in the inclusion questionnaire. Insufficient French literacy will not be used as an exclusion criterion at enrolment. Nevertheless, if analyses show that participants who do not speak and read French have outcome scores that are substantially and systematically lower than those of the rest of the sample, these participants may be excluded from planned sensitivity analyses to preserve data quality and comparability.

IPD will be shared under strict anonymity of participants, and only with approval from the ethics committee. In case the Ethics committee deems sharing of IPD inappropriate, data may not be shared.