We will undertake a systematic review of effectiveness and cost implications using established methods, based on those used by the National Institute for Health and Care Excellence (NICE) , and will report the findings according to the PRISMA guidelines . We will include evidence from repeated measures studies to RCTs that include a measure of change as an outcome of interest. The review has been registered with PROSPERO (registration number CRD42013006931).
The review will include studies conducted in any specific OHFO that serves, as its main business, ready-to-eat, prepared food for consumption on or off the premises. Specifically, in terms of setting, we will exclude OHFOs which are not openly accessible to the general public including those based in workplaces and educational institutions, or health or social care institutions. We will also exclude interventions in supermarkets and food stores (but supermarket and food store cafes will be included). The population of interest, therefore, will include customers of OHFOs (consumer level outcomes) as well as the businesses themselves (retail level outcomes).
The review will examine studies that have explored the effectiveness of any intervention that aims to change specific OHFOs in order to promote healthier menu offerings, including but not restricted to a reduction in energy intake. Interventions that focus exclusively on food hygiene or safety will be excluded. Examples of the types of interventions that we will expect to identify include those that focus on increasing the proportion of healthier food options available; promotions of healthier food options, food products or combinations; changing food formulation or cooking methods; and improving food and/or nutrition labelling.
Studies with and without comparators will be included in the review. There will be no restrictions on the type of comparator used in the study (for example, convenience comparison group, randomised control group, no intervention control and usual practice control).
Outcomes of interest will include consumer outcomes and retail outcomes. Consumer outcomes will fall under the headings of behaviour (for example, dietary fat intake), purchasing (for example, sales of healthier menu choices), attitudes (for example, acceptance of intervention and attitude towards healthier menu choice) and preferences (for example, choice of healthier menu items over less healthy items). Retail outcomes will include changes in retail practices (for example, regular fat mayonnaise replaced with a lower fat version), process outcomes (for example, number of times a salt shaker is refilled) and profit. All outcomes reported that fall into any of these categories will be explored in detail and results synthesised.
We will also identify and critically summarise relevant evidence (quantitative and qualitative, including process evaluations) on the development and implementation of the included OHFO interventions in order to capture recent innovation in intervention design and inform future intervention development. Further analysis of the interventions identified will be undertaken to identify the BCTs of the underlying processes that were changed as well as the techniques or strategies used to change them . We will also identify the modes of delivery, the intervention function (for example, environmental restructuring, incentivisation, training, education, and so on), and, if applicable, the policy category (for example, guidelines, regulation, legislation) in which the intervention fits. We will search for and identify a range of models/classifications of intervention modalities and choose one to use in the analysis alongside the BCT framework.
We will systematically search electronic databases for randomised controlled trials (RCTs), non-randomised controlled trials (NRCTs), controlled before-after studies (CBAs) and interrupted time series (ITS) studies. To the best of our knowledge, there is limited evidence from interventions of interest for this review from these types of study designs. Therefore, we propose to also include repeated measures studies and case series that have measured the experimental unit (for example, a group of people; the quantity of certain foods sold) before and after a single intervention; these studies do not include a control group.
We will search the databases MEDLINE (Ovid), EMBASE (Ovid), CINAHL (Ebscohost), PsycINFO (Ebscohost), ASSIA (ProQuest) and the NHS Economic Evaluation Database (Wiley Cochrane). In an attempt to locate studies of relevance to the current ‘foodscape’ and the global expansion of fast food and out-of-home eating culture , we will limit our searches to studies published in the last 20 years (from 1993 to current). Searches will be limited to articles written in the English language. An example search strategy in MEDLINE is attached as an Additional file 1. In order to ensure adequate sensitivity of the search strategy, HM has piloted the search in MEDLINE (searched 24 October 2013). This resulted in 2,261 hits, of which all five key indicator papers [21–25] that we had identified from our knowledge prior to running the search, were included.
We will also contact known topic experts from a range of countries and send enquiry Email messages, seeking information about published, unpublished and ongoing interventions that could be included in our review. We plan to include a separate list of ongoing studies as part of the review, which could be included in future updates of the review.
Data extraction and quality appraisal
Initial screening of titles and abstracts retrieved from the searches will be conducted by one reviewer (FH) with a random 10% of the sample independently screened by a second reviewer (AL). Full papers/reports of potentially relevant publications will be located and independently appraised by two researchers (FH and AL) to select those meeting the inclusion criteria. Data extraction and quality assessment of all included papers/reports will be conducted independently by two reviewers (FH and AL). Throughout, any discrepancies will be resolved through discussion with a third reviewer (CS). An electronic data extraction form has been developed and piloted to ensure consistency in data extraction between reviewers. Data to be extracted will include details of the project (aims, settings targeted, intervention description, resources, date started, date completed, study sponsor or funding source, and so on), study details (study design, population targeted, demographics, recruitment and follow-up rates, and so on), implementation information (context, experience of planners/implementers, collaboration, delivery fidelity, and so on), outcomes measured (and methods), and results. The quality of quantitative studies will be assessed using the Effective Public Health Practice Project Quality Assessment Tool for Quantitative Studies  as recommended by the Cochrane Public Health Review Group , and the Evaluation Tool for Qualitative Studies  will be used to assess the quality of qualitative studies.
Analysis and synthesis
We will analyse the results using established methods, based on those used by the National Institute for Health and Care Excellence (NICE) . Narrative synthesis will be conducted following the Economic and Social Research Council (ESRC) Narrative Synthesis Guidance . Interventions will be grouped according to their intervention function and policy category, as well as the type of OHFO in which they are set. Any qualitative data will be analysed and synthesised thematically. We plan to match qualitative findings with quantitative findings using cross study synthesis as suggested by the Evidence for Policy and Practice Information and Co-ordinating Centre . We will report our findings in accordance with PRISMA guidelines .