Several interventions encouraging people to change their diet have been tested in low- and middle-income countries (LMICs) but these have not been meta-synthesised and it is not known which elements of these interventions contribute to their effectiveness. The current review addressed these issues. Randomised controlled trials of dietary interventions in LMICs were eligible and identified via eight publication databases. Elements of both the intervention and comparison groups (e.g., behaviour change techniques (BCTs), delivery mode), participant characteristics and risk of bias were coded. Random effects meta-analysis of 76 randomised controlled trials found, on average, small- to medium-sized but highly heterogeneous improvement in dietary behaviour following an intervention. Small and homogeneous improvements were found for BMI/weight, waist- and hip-circumference, with medium-sized, but heterogeneous, improvements in blood pressure and cholesterol. Although many BCTs have yet to be tested in this context, meta-regressions suggested some BCTs (action planning, self-monitoring of outcome(s) of behaviour; demonstration of behaviour) as well as individually randomised trials, adult- or hypertensive-samples and lack of blinding were associated with larger dietary behaviour effect sizes. Interventions to encourage people from LMICs to change their diet produce, on average, small-to-medium-sized effects. These effects may possibly be increased through the inclusion of specific BCTs and other study elements.
Keywords: Diet; behaviour change interventions; low-income countries; meta-analysis; middle-income countries; systematic review.