Professional engagement and implementation appraisal in China’s national nutrition week: a nationwide cross-sectional study

National Nutrition Week (NNW) is a nationwide nutrition promotion campaign in China that depends on professionals to interpret campaign messages, organise local activities, and support public-facing delivery. However, evidence on professionals’ campaign knowledge, professional engagement, and implementation appraisal remains limited. We examined associations between these domains among professionals involved in NNW implementation in China. In this nationwide cross-sectional survey, professionals involved in NNW implementation were recruited through professional networks across all 31 provincial-level administrative regions of China between September 2025, and January 2026. The survey measured NNW campaign knowledge; three engagement indicators, comprising participation mode, participation breadth and toolkit use; and implementation appraisal. Multivariable regression, restricted cubic spline analysis, and exploratory mediation analysis were conducted, with adjustment for region, sex, age group, education level, professional title, and institution type. Of 5873 submitted responses, 4520 valid questionnaires were analysed. Higher NNW campaign knowledge was associated with more favourable implementation appraisal (β = 2.52, 95% CI: 2.14–2.91) and greater engagement, including greater participation breadth (OR = 1.36, 95% CI: 1.29–1.44), participation through both online and offline modes (OR = 1.70, 95% CI:1.50–1.92), and toolkit use (OR = 1.67, 95% CI: 1.57–1.78). Participation breadth showed a nonlinear association with appraisal, with the positive association attenuating beyond approximately six communication channels or delivery settings. In exploratory mediation analyses, engagement indicators partly accounted for the association between campaign knowledge and implementation appraisal, with estimated proportions mediated of 20.4% for participation mode, 17.7% for participation breadth, and 12.4% for toolkit use. Professional engagement was multidimensional and partly accounted for the association between campaign knowledge and implementation appraisal. Future programmes may benefit from clearly defined professional roles, a well-supported mix of communication channels and delivery settings, accessible campaign toolkits, and implementation indicators capturing professional preparedness, role clarity, and delivery quality.