A systematic review of adaptations and effectiveness of scaled-up nutrition interventions.

Context: Public health nutrition interventions shown to be effective under optimal research conditions need to be scaled up and implemented in real-world settings.

Objectives: The primary aim for this review was to assess the effectiveness of scaled-up public health nutrition interventions with proven efficacy, as examined in a randomized controlled trial. Secondary objectives were to: 1) determine if the effect size of scaled-up interventions were comparable to the prescale effect, and; 2) identify any adaptations made during the scale-up process.

Data Sources: Six electronic databases were searched and field experts contacted.

Study Selection: An intervention was considered scaled up if it was delivered on a larger scale than a preceding randomized controlled trial ("prescale") in which a significant intervention effect (P ≤ 0.05) was reported on a measure of nutrition.

Data Extraction: Two reviewers independently performed screening and data extraction. Effect size differences between prescale and scaled-up interventions were quantified. Adaptations to scale-up studies were coded according to the Adaptome model.

Results: Ten scaled-up nutrition interventions were identified. The effect size difference between prescale trials and scaled-up studies ranged from -32.2% to 222% (median, 50%). All studies made adaptations between prescale to scaled-up interventions.

Conclusion: The effects of nutrition interventions implemented at scale typically were half that achieved in prior efficacy trials. Identifying effective scale-up strategies and methods to support retainment of the original prescale effect size is urgently needed to inform public health policy.

Systematic Review Registration: PROSPERO registration no.CRD42020149267.