BACKGROUND: There is a need to identify and analyse the range of models developed to date for delivering health-related lifestyle advice (HRLA), or training, for effectiveness and cost-effectiveness in improving the health and well-being of individuals and communities in the UK, with particular reference to the reduction of inequalities. OBJECTIVES: To identify the component intervention techniques of lifestyle advisors (LAs) in the UK and similar contexts, and the outcomes of HRLA interventions. DATA SOURCES: Stakeholder views, secondary analysis of the National Survey of Health Trainer Activity, telephone survey of health trainer leads/coordinators. A search of a range of electronic databases was undertaken [including the Applied Social Sciences Index and Abstracts (ASSIA), EMBASE, NHS Economic Evaluation Database (NHS EED), MEDLINE, Psyc INFO, etc.], as well searching relevant journals and reference lists, conducted from inception to September 2008. REVIEW METHODS: Identified studies were scanned by two reviewers and those meeting the following criteria were included: studies carrying out an evaluation of HRLA; those taking place in developed countries similar to the UK context; those looking at adult groups; interventions with the explicit aim of health improvement; interventions that involved paid or voluntary work with an individual or group of peers acting in an advisory role; advice delivered by post, online or electronically; training, support or counselling delivered to patients, communities or members of the public. After quality assessment, studies were selected for inclusion in the review. Data were abstracted from each study according to an agreed procedure and narrative, and realist and economic approaches were used to synthesise the data. Cost-effectiveness analysis of interventions was undertaken. RESULTS: In total, 269 studies were identified but 243 were excluded. The 26 included studies addressing chronic care, mental health, breastfeeding, smoking, diet and physical activity, screening and human immunodeficiency virus (HIV) infection prevention. Overall, there was insufficient evidence to either support or refute the use of LAs to promote health and improve quality of life (QoL), and thus uncertainty about the interventions' cost-effectiveness. However, the economic analysis showed that LA interventions were cost-effective in chronic care and smoking cessation, inconclusive for breastfeeding and mental health and not cost-effective for screening uptake and diet/physical activity. LA interventions for HIV prevention were cost-effective, but not in a UK context. LIMITATIONS: The wide variety of LA models, delivery settings and target populations prevented the reviewers from establishing firm causal relationships between intervention mode and study outcomes. CONCLUSIONS: Evidence was variable, giving only limited support to LAs having a positive impact on health knowledge, behaviours and outcomes. Levels of acceptability appeared to be high. LAs acted as translational agents, sometimes removing barriers to prescribed behaviour or helping to create facilitative social environments. Reporting of processes of accessing or capitalising on indigenous knowledge was limited. Ambiguity was apparent with respect to the role and impact of lay and peer characteristics of the interventions. A future programme of research on HRLA could benefit from further emphasis on identification of needs, the broadening of population focus and intervention aims, the measurement of outcomes and the reviewing of evidence. FUNDING: This study was funded by the Health Technology Assessment programme of the National Institute for Health Research.