SummaryObesity and diet‐related noncommunicable diseases (NCDs) have a profound impact on individuals, households, health care systems, and economies in low‐ and middle‐ income countries (LMICs), with the Western Pacific Region experiencing some of the highest impacts. Governments have committed to improving population diets; however, implementation challenges limit effective policy action. We undertook meta‐narrative synthesis of the academic literature and used theories of policymaking and implementation to synthesize current knowledge of issues affecting the adoption and implementation of policies to prevent obesity and diet‐related NCDs in LMICs in the Western Pacific Region. We found that political leadership and management of food and nutrition policies often diluted following policy adoption, and that nutrition and health advocates find it difficult to enforce policy compliance from actors outside their sectors. Opportunities for strengthening implementation of food and nutrition policies in the Western Pacific include (1) improved and earlier engagement between health policymakers and implementing agencies; (2) focusing on the need for increased accountability from governments, including through effective engagement and organization of actor networks, knowledge sharing, and in highlighting where stronger action is required; and (3) identifying and building the strategic capacities of policy actors in framing, advocacy, coalition‐building, knowledge translation, and leadership.