Introduction:Healthy diets are generally more expensive than unhealthy diets, explaining why socially disadvantaged individuals perceive food prices as a barrier to improve their diets. It is thus crucial to develop strategies enabling the achievement of good nutritional quality with a low budget, taking into account actual beliefs and expectations of the target population. A co-construction approach is thus recommended, involving participants at each step of the intervention to maximize its impact.Methods:The “Opticourses” program was launched in 2010 with a feasibility study, followed by an intervention research in 2012-2014, in order to develop and evaluate a prevention program aiming at improving the nutritional quality of food purchases at no additional cost in a socioeconomically disadvantaged population. In order to implement activities tailored to the target population, participants were involved in the development of the protocol and the tools of the intervention and evaluation processes.Results:Opticourses’s workshops (8 to 12 participants) include different activities displayed in four 2h sessions around real food purchases of participants, and games and exchanges aimed at promoting food and food choices of good nutritional quality for their price. The intervention research showed improvements in food purchasing behaviors of Opticourses participants. A transferability phase was conducted in 2015-2017. Since 2017, Opticourses is spreading in several regions of France, through training of professionals, in particular the courses organized by the Health Education Regional Committee (CRES) in the South of France.Discussion:Bringing an original, concrete, co-constructed and scientifically based response to an everyday life problem is the main strength of the program. One important risk of failure for such prevention program is the underestimation of the requirements of the intervention research, in terms of time and human and budgetary resources.