The Dutch government encourages municipalities to develop 'Health in All Policies' (HiAP). The development of such a policy requires inter-sectoral collaboration, however municipalities show little initiative in this regard. Operating in an advisory role, the regional Public Health Service (PHS) has supported municipalities in South-Limburg in setting up inter-sectoral collaboration. A coaching program for municipal stakeholders was developed and implemented to improve HiAP, using obesity as an example. To determine the effectiveness of this coaching program, civil servants, managers and municipal councilors were invited to fill in an Internet questionnaire prior to and at the completion of the program. By means of a log-book all activities were registered in coached municipalities and in-depth interviews were held with municipal managers. Outcomes were scored depending on the stage of HiAP proposals. Six of the nine coached municipalities showed concrete outcomes in terms of HiAP proposals. The results show that more support and involvement at each system level stimulates the development of HiAP. The program contributed positively to the implementation of HiAP interventions targeting obesity. The pretest results for coached municipalities were better compared to non-coached municipalities. However, after 30 months of coaching this positive starting position faded away. We recommend that the municipal management become more involved in the development of HiAP and advise the PHS to increasingly demonstrate their expertise. Here lies a challenge for municipalities and their regional PHS.