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.