["Health Expectations, Volume 29, Issue 2, April 2026. ", "\nABSTRACT\n\nBackground\nThe design process of public health promotion programmes is rarely described in detail. This study aims to present the co‐design process and theoretical rationale of a diet‐ and physical activity‐promoting programme called ALAPAGE, targeting community‐dwelling adults aged 60 years and older in southeastern France.\n\n\nMethods\nThe six steps of the Intervention Mapping (IM) framework applied to the ALAPAGE programme were as follows:\n\n1.\nNeeds assessment: Eighteen participatory meetings with stakeholders and a literature review were conducted to identify determinants of behaviour change.\n2.\nIdentification of change objectives (immediate targets of the ALAPAGE programme).\n3.\nIntervention theory: Based on the literature and health psychology expertise, Theory of Planned Behaviour and Goal Setting Theory were used supplemented by behaviour change techniques. These were adapted to the change objectives and translated into practical strategies.\n4.\nDevelopment of the ALAPAGE programme sequences.\nSteps 5 (implementation) and 6 (evaluation) are described in a separate article.\n\n\nResults\nFollowing IM, 31 change objectives were defined, adapted to 15 determinants of behaviour change (e.g., setting a personalised goal was selected as a change objective to address the determinant ‘experimenting with behaviour’). Thirty practical strategies (e.g., group discussions) were organised into seven group sessions. Nineteen pedagogical tools (e.g., 24‐h recall sheets) were tested in a pilot study involving 21 participants.\n\n\nConclusion\nUsing the IM approach, the ALAPAGE programme integrates behaviour change techniques to simultaneously address determinants of diet and physical activity among seniors.\n\n\nPublic Contribution\nProfessionals from partner organisations contributed to needs assessment, and programme development. Dieticians and physical activity specialists helped identify behaviour change determinants, validated the theoretical model, and participated in programme design and testing. Seniors were interviewed during the needs assessment and tested the programme sequence.\n\n\nTrial Registration\nClinicalTrials.gov identifier: NCT05 140330, 1 December 2021, https://www.clinicaltrials.gov/study/NCT05140330?titles=ALAPAGE&rank=1.\n"]