There is an urgent need to find effective methods of supporting individuals to make dietary behaviour changes. Peer-supported interventions (PSI) have been suggested as a cost-effective strategy to support chronic disease self-management. However, the effect of PSI on dietary behaviour is unclear. The present systematic review aimed to assess the effectiveness of PSI for encouraging dietary behaviour change in adults and to consider intervention characteristics linked with effectiveness.

Electronic databases were searched until June 2018 for randomised controlled trials assessing the effectiveness of PSI compared with an alternative intervention and/or control on a dietary related outcome in adults. Following title and abstract screening, two reviewers independently screened full texts and data were extracted by one reviewer and independently checked by another. Results were synthesised narratively.

Randomised controlled trials.

Adult studies.

The fifty-four included studies varied in participants, intervention details and results. More PSI reported a positive or mixed effect on diet than no effect. Most interventions used a group model and were lay-led by peer supporters. Several studies did not report intervention intensity, fidelity and peer training and support in detail. Studies reporting positive effects employed more behaviour change techniques (BCT) than studies reporting no effect; however, heterogeneity between studies was considerable.

As evidence was mixed, further interventions need to assess the effect of PSI on dietary behaviour, describe intervention content (theoretical basis, BCT, intensity and peer training/support) and include a detailed process evaluation.