Healthy eating interventions conducted in small, local restaurants and hot food takeaways: a systematic review

Abstract

Objective:

This systematic review investigates the characteristics, effectiveness and acceptability of interventions to encourage healthier eating in small, independent restaurants and takeaways.

Design:

We searched five databases (CENTRAL, MEDLINE, Embase, CINAHL and Science Citation Index and Social Science Citation Index) in June 2022. Eligible studies had to measure changes in sales, availability, nutritional quality, portion sizes or dietary intake of interventions targeting customer behaviour or restaurant environments. We evaluated study quality using the Mixed Methods Appraisal Tool. Results are synthesised narratively, and interventions’ impact on personal autonomy is assessed using the Nuffield intervention ladder.

Setting:

Small, independent or local restaurants or hot food takeaway outlets, with no restrictions by year or country.

Participants:

Anyone selling or purchasing food in intervention settings (e.g. restaurant staff/owners, customers).

Results:

We screened 4624 records and included 12 studies describing 13 interventions in 351 businesses. Most studies were of poor quality. Customer-level intervention components mostly operated on the lower rungs of the Nuffield ladder, and most had limited positive effects on increasing demand, measured as sales or orders of healthy options. Whilst rare, most interventions measuring business outcomes operated on higher ladder rungs and showed small positive results. There was insufficient evidence to investigate differences in impact by intervention intrusiveness. Acceptability was greater for interventions that were low-effort, inexpensive and perceived as not negatively impacting on customer satisfaction.

Conclusions:

Despite some evidence of small positive effects of healthy eating interventions on healthier purchases or restaurant/hot food takeaway practices, a weak evidence base hinders robust inference.

One in five deaths worldwide is linked to poor diet⁽¹⁾. Food consumed out of the home in restaurants, cafes and takeaways tends to be high in calories⁽²⁾, saturated fat⁽³⁾ and salt⁽⁴⁾, with more regular consumption linked to an increased risk of higher body weight⁽⁵⁾. A 2022 survey conducted by the Food Standards Agency in England, Wales and Northern Ireland found that 53 % of respondents had eaten in a restaurant, 50 % had ordered takeaway food and 38 % had consumed food from a fast-food outlet in the previous 4 weeks⁽⁶⁾. Evidence from high-income countries also suggests fast-food outlets are more common in deprived communities compared with more affluent areas^(7–9).

Small businesses dominate the sector, with just over half of the £62 billion of revenue generated from the UK consumer foodservice sector in 2022 coming from small and locally owned restaurants and hot food takeaways⁽¹⁰⁾. Unlike large chain restaurants, small independent businesses usually operate in small premises, with limited staff, equipment and access to suppliers⁽¹¹⁾, and finite resources to participate in healthy eating interventions specifically⁽¹²⁾. Yet in contrast to large, chained businesses, owners of small independent businesses may be more likely to be able to make decisions about whether and how to enact interventions⁽¹³⁾.

A study found that independent and small-chain restaurants (under twenty outlets) serve meals with higher energy content than those in larger chain restaurants, with individual meals accounting for 66 % of an adult’s daily energy requirements⁽¹⁴⁾. Nevertheless, existing reviews on healthier eating interventions in restaurants, takeaways and fast-food outlets mostly rely on large chain restaurants⁽¹⁵⁾ or include both chains and non-chains^(16,17) , and policies aiming to support healthier food purchasing in the out-of-home sector (e.g. nutrition labelling) have typically only applied to larger businesses who have greater resources to implement such legislation^(18,19) . However, this risks widening health inequalities if the small businesses exempt from them provide less healthy food and are more abundant in predominantly poorer areas. Indeed, evidence from Australia shows that independent takeaways are more common in deprived than affluent areas⁽²⁰⁾ and studies from the UK describe a high prevalence of independent fast-food and takeaway outlets in disadvantaged areas^(21,22) . Therefore, separate interventions are needed for small, independent restaurants, which are effective in improving food healthiness whilst being feasible and acceptable to restaurants. For example, in the case of menu labelling, a survey among independent restaurants in Canada found that common worries are the expenses and time effort required to implement such a policy⁽²³⁾.

The differences between chained and independent restaurants and takeaways mean that policymakers need specific information on the types of interventions that may be effective in small restaurants and hot food takeaways, including potential challenges and opportunities to developing effective interventions. We aimed to systematically review the extant evidence of interventions to promote healthier food purchasing or consumption in this setting.

The objectives of this review were to:

1. 1. Establish the characteristics of healthy eating interventions conducted in small, independent or local restaurants and hot food takeaways (hereafter ‘restaurants and takeaways’).

2. 2. Assess the impact these interventions had on food availability and purchasing patterns.

3. 3. Identify characteristics of interventions that increased acceptability to small restaurant and takeaway staff and owners.

The findings of this review can inform policymakers on which interventions may be effective and acceptable in small independent restaurants and takeaways and can be implemented at a local level.

Methods

Protocol and registration

The pre-registered protocol is available on PROSPERO (CRD42022341791). This review follows the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 checklist for reporting systematic reviews⁽²⁴⁾ (Appendix 1).

A review with a wider scope was specified in the protocol including healthier eating interventions in small food stores and restaurants. However, after completing data extraction, we split the review into two papers to focus on each setting in isolation. Instead of using the National Institutes of Health Quality Assessment Tools⁽²⁵⁾ as pre-specified, we used the Mixed Methods Appraisal Tool (MMAT)⁽²⁶⁾, which enabled us to evaluate different study types employing one tool and guidance document.

Data sources and search strategy

The search strategy for this review was tailored to identify interventions in small restaurants and takeaways and food stores. An information specialist (NR) developed the search strategy in consultation with LB after initial scoping searches. We searched the following databases for primary studies from database inception to 15 June 2022: Cochrane Central Register of Controlled Trials (CENTRAL), Issue 5, 2022, the Cochrane Library (Wiley), MEDLINE and Epub Ahead of Print, In-Process & Other Non-Indexed Citations and Daily (OvidSP, 1946–), Embase (OvidSP, 1974–), CINAHL (EBSCOhost, 1982–) and Science Citation Index and Social Science Citation Index (Web of Science Core Collection, 1900–). Search strategies were comprised of keywords and controlled vocabulary terms. We applied no limits on language or publication date. We used the filter designed by the Cochrane EPOC group to identify randomised studies, before and after studies and interrupted time series (https://zenodo.org/record/5106292). We used the Polyglot tool from SR-accelerator (https://sr-accelerator.com/#/polyglot) to adapt the search formatting from MEDLINE to the other databases. All search strategies are provided in Appendix 2A.

All references were downloaded to Endnote 20⁽²⁷⁾ before being transferred to Covidence⁽²⁸⁾. In November 2022, we additionally conducted forward and backward searches of eligible studies and six reviews^{(15,16,29–32)} using Citation Chaser⁽³³⁾, with results subsequently imported into Covidence⁽²⁸⁾. We excluded two more restaurant and takeaway papers^(34,35) after the citation tracking due to them not meeting our setting or outcome requirements.

Eligibility criteria

Eligibility criteria were determined following the population, intervention, comparison, outcome and study design (PICOS) framework⁽³⁶⁾ and are outlined in Table 1. We included primary studies where the study authors described the restaurant or takeaway as small, independent, community-based or local and where there was no evidence that the restaurants or takeaways were part of a chain. A community-based restaurant was defined as a place for local people to come together to eat freshly cooked food.

Table 1. Eligibility criteria based on population, intervention, comparison, outcome and study design (PICOS)⁽³⁶⁾

* Exclusion of theses, dissertations, protocols, trial registrations and conference abstracts as well as national-level interventions was decided after the review had begun.

Study selection and data extraction

After the exclusion of duplicates, abstract and full-text screening was completed independently and in duplicate by two reviewers (LB and CJ) using Covidence⁽²⁸⁾. Any conflicts were discussed by the two reviewers, and a third reviewer arbitrated if needed.

Data extraction was conducted by one reviewer, with reviewers subsequently checking the data extraction forms completed by the other reviewer. Again, any conflicts were discussed and resolved between the two reviewers. Data extracted included first author name and year, country and location, stakeholders involved, study aim, methods (design, start and end date, targeted population, co-design and stakeholder involvement, if applicable), setting type, sample size, recruitment methods, inclusion criteria, intervention characteristics (name, description, duration, comparator/control), outcomes, measured data, statistical or analysis methods, main findings, barriers and facilitators to working with businesses and recommendations for future studies.

Study quality assessment

Study quality was rated independently by one reviewer and verified by a second reviewer (LB or CJ) using the MMAT⁽²⁶⁾. Each of the included studies was first categorised into one of five groups based on study design: (i) qualitative research; (ii) randomised controlled trials; (iii) non-randomised studies; (iv) quantitative descriptive studies; and (v) mixed methods studies. Studies were then assessed for quality using the category-specific criteria and presented in full, as recommended, rather than being adapted into a single score⁽²⁶⁾.

Synthesis of results

Results were synthesised narratively⁽³⁷⁾. The main characteristics and outcomes of interventions were summarised in tables, and the patterns were identified. Additionally, our analysis was guided by the Nuffield intervention ladder⁽³⁸⁾, which categorises interventions according to their intrusiveness (i.e. their impact on individual freedom) (Table 2). Briefly, higher steps on the ladder represent more intrusive interventions, with eliminating choice being the highest step (i.e. most intrusive intervention)⁽³⁸⁾. Each element of the included interventions was grouped depending on whether it was designed to impact consumer behaviour (customer-level interventions) or the business’s behaviour (business-level intervention).

Table 2. The Nuffield intervention ladder⁽³⁸⁾, used for categorising included interventions

Results

Searches retrieved a total of 7455 records, and after removing duplicates, 4624 records were screened (Fig. 1). We assessed 287 full-text records for eligibility, resulting in the inclusion of 12 studies reporting on 13 interventions.

Fig. 1 PRISMA flow diagram showing the study selection process⁽²⁴⁾.

Quality assessment

Of the twelve studies included, most used a mixed methods^(39–43) (n 5) or a quantitative, non-randomised^(13,44–46) (n 4) study design (Table 3). Two were randomised controlled trials^(47,49) , and one study was quantitative descriptive⁽⁴⁸⁾. No qualitative studies were identified, potentially due to our outcomes of interest being geared towards quantitative measurements.

Table 3. Study quality assessment of included studies using MMAT⁽²⁶⁾

MMAT, Mixed Methods Appraisal Tool; N, no; Y, yes; C, can’t tell. MMAT study design group: 2 = randomised controlled trial; 3 = quantitative non-randomised study; 4 = quantitative descriptive study; 5 = mixed methods study. Questions for each study design were as follows in Appendix 2B.

Neither of the randomised controlled trials^(47,49) met all of the MMAT’s⁽²⁶⁾ quality criteria. Randomisation was either not appropriately performed⁽⁴⁷⁾ or insufficiently described⁽⁴⁹⁾, and neither study reported whether outcome assessors were blinded to the intervention, which limited their quality assessment scores.

Only one of the four quantitative, non-randomised studies provided sufficient detail to be appraised and met all five criteria⁽⁴⁴⁾. Other studies provided insufficient detail on the population’s representativeness⁽⁴⁶⁾, whether there were complete outcome data^(13,45) , whether confounders had been accounted for^(13,46) and whether the intervention was implemented as intended⁽⁴⁶⁾.

One study was a quantitative descriptive study⁽⁴⁸⁾. It met the criteria for sampling strategy and statistical analysis but provided insufficient information or did not meet the criteria for representativeness of the sample, appropriateness of variables and measurements and the risk of non-response bias.

Five studies were mixed methods^(39–43). Whilst all were strong on integrating qualitative and quantitative components of their research questions, they did not provide sufficient information on or failed to address the divergences and inconsistencies between quantitative and qualitative findings. Some also failed to meet the criteria of providing an adequate rationale for using mixed methods^(39,40,43) , integrating quantitative and qualitative interpretation⁽⁴¹⁾ and adhering to the quality criteria of the different methods involved^(39,40,43) .

Settings and stakeholders involved in the interventions

Twelve studies reporting on thirteen interventions were included, with two papers assessing the same intervention^(44,45) and two papers testing two interventions each^(47,49) . Eight interventions involved small restaurants^{(40,41,46–49)} , three focused on takeaway outlets^{(13,39,44,45)} and two included both^(42,43) . The number of businesses involved varied, ranging from one^(48,49) to 206⁽¹³⁾ (Table 4).

Table 4. Intervention name, location, study design and stakeholders involved in included studies

RCT, randomised controlled trial; WA, Washington; CA, California; MD, Maryland; PA, Pennsylvania.

Ten interventions were conducted in the USA^{(13,40,41,44–49)} and three in the UK^(39,42,43) . Most took place in cities^{(13,41,44,45,48)} , highly populated counties^(47,49) , boroughs⁽⁴²⁾ or suburban areas⁽⁴⁶⁾. One intervention was set in rural small-town settings⁽⁴⁰⁾, and one included both urban and rural settings⁽⁴³⁾. Although not all studies provided this information, several targeted low-income areas^{(13,41,44,45)} , and others spanned areas with various levels of deprivation^(39,42,43) . All but three interventions^(40,47) engaged a wider range of stakeholders other than businesses and academic researchers, commonly from the local authority (n 6; e.g. health teams, environmental health officers)^{(13,39,41,42,46,48)} or local community organisations or non-governmental organisations (n 3)^(13,41,48) .

Some interventions focused on specific cuisines, such as American^(40,47) , Latino⁽⁴⁷⁾, Chinese⁽¹³⁾ or British ‘Fish & Chip’ shops⁽⁴³⁾. Two interventions had inclusion criteria relating to business owner ethnicity, targeting African-American or Korean-American takeaway owners^(44,45) or Chinese American restaurant owners or chefs⁽¹³⁾. Several interventions conducted in the USA were set in areas with a high or growing proportion of residents identifying as Latino or Hispanic^(41,47–49) , African American^(44,45) or areas with a high proportion of ethnic minority residents⁽¹³⁾.

Interventions based on their classification on the Nuffield intervention ladder

Almost all interventions had components classed as ‘customer-focused’ as well as ‘business-focused’^{(13,39,41–49)} , with one intervention solely aimed at the customer level⁽⁴⁰⁾ (Table 5). All but three interventions operated on more than one rung of the Nuffield ladder^(40,47,49) . The highest rung used was restricting choice on the business level^(39,42) . The lower Nuffield ladder classifications that ‘provide information’ and ‘enable choice’ were most commonly used, aimed at both customers (e.g. menu labelling) and business owners and staff (e.g. cooking guidelines for chefs) (Table 5).

Table 5. Included interventions coded by the Nuffield intervention ladder⁽³⁸⁾

Business-level intervention components and outcome measures

Five interventions measured business-level outcomes^{(13,39,41–43)} (Table 6). Three studies used the number of businesses meeting certain criteria as an outcome measure^(39,42,43) , and three studies measured the nutrient content or weight of dishes sold^(13,41,43) , with one also describing self-reported changes to cooking habits⁽⁴¹⁾. Four studies only provided descriptive evaluations^(39,41–43) .

Table 6. Summary of intervention characteristics, outcome measures and main findings

Four interventions resulted in small increases in the number of businesses complying with criteria^(39,42,43) , reduced weight of sold meals⁽⁴³⁾ or sodium content of dishes⁽¹³⁾. One intervention described staff reporting positive changes to cooking habits⁽⁴¹⁾.

Restrict choice

Three interventions^(13,39,42) aimed to reduce the sugar, fat and salt content of foods, for example, by changing cooking practices (e.g. cooking oil usage) or switching to healthier products. Two used the number of businesses and number of criteria met as outcome measures and reported small positive effects^(39,42) , whilst another recorded lower sodium content of dishes⁽¹³⁾. However, only one conducted statistical testing⁽¹³⁾.

The Healthy Catering Commitment in London is a series of criteria relating to cooking, serving and selling practices; businesses are expected to meet eight out of twenty-two criteria before being awarded a Healthy Catering Commitment Award by their local authority⁽⁴²⁾. Seventy-seven businesses were surveyed, each having to make an average of 2·5 criteria-related changes to secure the award⁽⁴²⁾. More businesses (n 26) signed up for ‘provision of information’ (e.g. promotion of healthy eating by staff) compared with ‘enabling choice’ criteria (n 1–15, depending on change) (e.g. offering fresh fruit, smaller portion sizes) due to cost and potentially reduced revenue associated with the latter. Criteria to ‘eliminate choice’ that were cheap and perceived as not interfering with customer preferences (e.g. cooking oil practices) were readily implemented; however, there was more hesitancy for changes visible to customers (e.g. thick-cut chips).

Similarly, the Takeaway Masterclass intervention asked businesses to commit to health-promoting practices and provided interactive training⁽³⁹⁾. Businesses committed to a median of 4 goals/criteria (range 1–7) and achieved a median of 3 goals, including increasing vegetables in meals and grilling and poaching instead of frying⁽³⁹⁾.

The Healthy Chinese Take-out Initiative included a media campaign and low-sodium training, with takeaways adopting sodium-reduction techniques such as lowering the amount of soy sauce used⁽¹³⁾. A significant and sustained reduction in the sodium content of three target dishes was found, with relative reductions of 36 % for Dish 1 (5·5–3·5 mg/g), 28 % for Dish 2 (5·7–4·1 mg/g) and 19 % for Dish 3 (5·9–4·8 mg/g), although all three dishes remained above the local authority’s recommended sodium intake per meal⁽¹³⁾.

Guide choice through incentives

The Fish and Chip Wholesaler Study combined public pledging, provision of smaller-sized packaging and an information and engagement session⁽⁴³⁾. Although only reporting descriptive statistics, the number of venues offering smaller portion meals increased from 6 at baseline to 8 at 6-week post-intervention, and the weight of fish and chip meals sold decreased by a mean of 37 g for regular meals and 27 g for small meals⁽⁴³⁾.

Enable choice

Salud Tiene Sabor, a menu labelling intervention, reported restaurant staff declaring they employ healthier cooking practices as a result of the intervention, including using more vegetables⁽⁴¹⁾. They also tested meals served for their calorie content and found that post-intervention, 58 % of main meals and 59 % of side dishes remained above the local authority’s recommended calorie content per meal, although there was no baseline or control for comparison⁽⁴¹⁾.

Customer-related intervention components and outcomes

Ten interventions measured customer-related outcomes^{(40,41,43–49)} (Table 6). Nine interventions used value sales and/or order data to measure intervention impact on customer-related behaviour change^(40,43–49) , and six reported customer-interview data^{(40,41,43,45,49)} . Studies that used sales data reported challenges with data collection. There was heterogeneity in registers/tills across restaurants that made the data hard to process⁽⁴⁷⁾. Not all intervention restaurants and takeaways provided data⁽⁴³⁾, and it was laborious to manually input paper order slips⁽⁴⁴⁾.

One intervention reported a positive effect on smaller portion size orders⁽⁴³⁾, although only evaluated descriptively. Three interventions found mixed results (positive and no changes) on healthy foods sold^(44,49) . Two interventions recorded no significant increases in healthy item orders^(40,46) . Three interventions reported orders occurred from the new healthier menu, but it was unclear if these replaced or supplemented orders from the existing menu^(47,48) . One intervention reported that nutrition information influenced the purchase decisions of one-third of customers, but there was no baseline comparison⁽⁴¹⁾.

Guide choice through incentives

Two interventions provided financial incentives for healthy meal choices through price promotions^(44,45) and donations to local causes⁽⁴⁹⁾, finding mixed effects (positive and no changes) on sales of healthier items depending on the item targeted⁽⁴⁴⁾ or comparison time period⁽⁴⁹⁾.

The Baltimore Healthy Carry-out intervention recorded a statistically significant interaction between groups for healthier sides and beverages sold in two of three intervention phases, but not for healthier entrees or healthy items overall⁽⁴⁴⁾. The greatest increase was seen in phase 3, where a price promotion (incentive) was implemented alongside healthier cooking methods^(44,45) . Although the effect of intervention phases cannot be isolated due to each new phase building on the previous one, this could suggest that intervention elements higher up the ladder may have been more successful within this study. In the process evaluation, 42·6 and 65·3 % of surveyed customers reported choosing an option due to the BHC leaf logo or photos on the menu, respectively⁽⁴⁵⁾. The Fundraising Healthy Eating Scheme intervention made higher financial donations to local schools contingent on orders of healthier menu items and found a higher percentage of healthier menu items ordered during the intervention than in the post-intervention period, but not in the pre-intervention period⁽⁴⁹⁾. Six of the surveyed customers (20·7 %) said they chose their meal option due to the incentive⁽⁴⁹⁾. There was no significant difference in orders of healthy items between the intervention arms (other arm reported under provide information)⁽⁴⁹⁾; suggesting adding a higher ladder level component (incentive) did not provide additional benefit in this instance.

Enable choice

Five interventions enabled choice by adding new healthier meals or sides to menus^(47,48) or marking healthy options on menus^(41,44–47) . Three recorded orders of new healthy items, but it remained unclear how order numbers from existing menus were affected^(47,48) . One intervention found no changes in healthy item orders⁽⁴⁶⁾. In one study, a third of clients stated their order was influenced by nutrition information, but there was no comparison⁽⁴¹⁾.

The Kids Choice Restaurant Program created new healthier menus in both interventions, with one intervention additionally employing marketing and employee training⁽⁴⁷⁾. Both interventions recorded increased sales of new healthier menu items immediately after implementation, with the proportion of healthier items making up 23 % (menu plus) and 17 % (menu only) of all children’s menu items in the first four intervention weeks⁽⁴⁷⁾. However, sales of pre-existing menu items did not differ between the two conditions during the intervention, and the difference from baseline was not assessed statistically⁽⁴⁷⁾. The Galerias Restaurant intervention found that after 6 weeks, 11·6 % of item orders were from the new intervention menu, but there was no comparator, and it is unclear whether sales of less healthy items decreased⁽⁴⁸⁾. The Healthy Dining Program labelled and promoted healthy menu items and found no change in targeted healthy menu orders from pre-intervention to 6-week post-intervention⁽⁴⁶⁾. Salud Tiene Sabor found that one-third of customers stated their purchases were influenced by the point-of-sale nutrition information that was displayed during the intervention, but there was no pre-intervention comparator⁽⁴¹⁾.

Provide information

Three interventions provided information only, promoting healthier products using marketing materials such as table tents^(40,43,49) or providing point-of-purchase nutrition information⁽⁴⁹⁾. One intervention described slightly increased small-portion orders⁽⁴³⁾, however not using any statistical tests. One intervention found mixed results (positive and no effect)⁽⁴⁹⁾, and one had no effects on healthier orders⁽⁴⁰⁾.

The Fish and Chip Wholesaler Study encouraging fish and chip shop owners to offer and promote smaller portion sizes found increases in the number of small-portion meal orders from 14·2 % of total Fish & Chip orders before the intervention to 21·2 % post-intervention, with 20 % of surveyed customers indicating they had tried a smaller portion meal⁽⁴³⁾. The Signposting to Healthy Meals did not have a comparator group and found no significant changes in order slips, although 34 % of customers who were aware of the signs said that these had impacted their order⁽⁴⁰⁾. One intervention arm from the Fundraising Healthy Eating Scheme provided information on healthier items and a 15 % donation of the total bill value to the school wellness programme and recorded significantly increased healthy item orders compared with follow-up, but not the baseline period⁽⁴⁹⁾. Only four surveyed customers (10·8 %) said they selected their option due to the promotion materials⁽⁴⁹⁾.

Intervention barriers and facilitators

Recruitment of restaurants and takeaways can be challenging, with recruitment rates for businesses varying from 10⁽³⁹⁾ to 100 %⁽⁴⁰⁾ of those approached to participate in the evaluation. Four studies did not report recruitment rates^{(13,41,46,49)} . One research team was approached by a business owner wanting to conduct an intervention⁽⁴⁸⁾. Identifying and visiting potential restaurants and takeaways several times before recruitment was reported as a strategy for successful recruitment^(44,45) . One other study reported that a local restaurant association played a strategic role in recruiting restaurants⁽¹³⁾.

Five studies reported intervention fidelity, all achieving moderate to high fidelity^{(40,43,45,47,49)} . Three studies reported barriers relating to difficulties engaging busy restaurant and takeaway staff with the training⁽⁴⁷⁾, high turnover rates⁽¹³⁾ and trusting that staff would correctly deliver smaller portion sizes as intended⁽⁴³⁾. Framing the intervention as ‘good customer service’ was reported to be potentially beneficial to serving staff implementing the intervention as intended⁽⁴³⁾. Motivated staff, especially owners and managers, were key to keeping businesses engaged with and implementing the intervention^{(39,45,48,49)} . Building good relationships with owners and involving them in decisions⁽⁴⁵⁾ as well as building strong partnerships⁽¹³⁾, with, for example, support from community groups^(41,48) or working with a wholesaler⁽⁴³⁾, were also mentioned as facilitators.

Two studies reported that businesses are better engaged with intervention elements that were cheap, easy to implement and perceived as acceptable or less noticeable to clients, which included easy-to-implement intrusive interventions (e.g. changing cooking oil used, categorised as restrict choice)^(39,42) . One study reported that a two-phase intervention where low-cost, low-burden intervention elements are implemented first whilst building a stronger rapport with business owners and managers before introducing higher-burden intervention elements was effective at keeping businesses engaged^(44,45) . Conversely, worries about customer satisfaction, a lack of demand for healthier products and associated costs were common barriers^(39–42,45) . Six studies reported that an intervention’s economic impact is an important factor for business owners when considering whether to engage with interventions, primarily because of small restaurants’ and takeaways’ small profit margins and susceptibility to economic fluctuation^(40–45,48) . Businesses were reported to be motivated by the potential (financial) benefit of an intervention^(43,49) , positive feedback from clients⁽³⁹⁾ and financial incentives (e.g. supplies, covering first stock)⁽⁴⁵⁾.

One main barrier to implementation was a lack of availability of healthier products from suppliers, either at all or at a comparative price point to regular versions^(39,42) . This may be more common in more rural areas and outside of large cities⁽³⁹⁾, and both businesses and customers in more affluent areas may be more willing to pay the extra costs involved in healthier options⁽⁴²⁾.

A web-based tool kit was a useful tool for dissemination of lessons learned and for potential participating businesses to learn more about the intervention⁽⁴¹⁾.

Discussion

Summary of findings

Interventions to encourage healthy eating in small, independent restaurants and takeaways were mostly a complex mix of initiatives integrating business-level elements and consumer-focused components. Study quality was poor with limited quantitative outcome data, and it was not possible to conduct a meta-regression to identify effective components. Nonetheless, we found some narrative themes. Interventions focused at the customer level were mostly at the lower rungs of the Nuffield ladder. Enabling choice through introducing new and healthier menu items resulted in healthier items being ordered, with take-up varying from 11⁽⁴⁸⁾ to 23 %⁽⁴⁷⁾ of orders, but it was less clear whether these items substituted or supplemented other less healthy items. There was also a lack of evidence on whether the uplift in sales when new menu items were introduced could be sustained. Providing incentives (at the mid-point of the ladder) also resulted in a mix of positive results and no effect, with impact varying across product categories or comparison periods. Price promotions appeared to have some effect at least in the short term to boost sales of healthy products⁽⁴⁴⁾ but may not be a sustainable option for small businesses with tight margins. Most business-level interventions were classified as operating at mid-to-high rungs of the Nuffield ladder. Few interventions evaluated business-level outcomes, but almost all reported some positive effect including greater adherence to nutritional criteria or reduced salt content or weight of dishes, though quantitative evidence of effectiveness was scarce.

Strengths and limitations

We comprehensively searched relevant academic databases, including through multiple screeners and new software (e.g. Citation Chaser⁽³³⁾), building confidence in the scope and accuracy of our review. Our synthesis of studies provides the first overview to identify characteristics that are important for successful intervention design and implementation to improve food healthiness in small restaurants. We used the Nuffield intervention ladder to categorise intervention components; two included studies similarly used the Nuffield ladder to characterise intervention components^(39,42) , whilst another study reflected on their results using the Nuffield ladder⁽⁴³⁾, highlighting the relevance of this framework. Although we risk excluding studies by not conducting additional grey literature searches, higher-quality studies would likely be published in peer-reviewed journals.

The small number of heterogeneous and relatively low quality studies identified in the review is in itself a finding of interest but limits the potential generalisability of these results. Few studies had a randomised design, and it was not possible to directly compare interventions due to the heterogeneity of intervention components, study designs and settings. Furthermore, the narrow geographic range (urban areas in the UK and USA) of studies included means that findings may not translate to other food cultures (e.g. informal food economies). Additionally, our review may be limited by publication bias⁽⁵⁰⁾, particularly considering most interventions described at least some positive effects.

Interpretation and comparison to existing literature

To the best of our knowledge, this is the first review that has focused specifically on small, independent restaurants and takeaways. The poor quality of available evidence and lack of impact evaluations in the out-of-home field have been reported in previous reviews^(15–17,51) . For example, in a review summarising interventions in food outlets in England, only twenty-one out of seventy-five interventions included evaluations of the impact or outcome of the intervention, and such evaluations were done to aid service delivery rather than research-led initiatives⁽⁵¹⁾. Challenges with data collection as reported by many studies in this review may impede rigorous evaluation.

Previous reviews also found that ‘simple’ environmental changes such as information provision and promoting existing healthy options are particularly common intervention strategies in community-based restaurants^(16,17) , consistent with our finding that easily implemented and cheap interventions are most acceptable to businesses. One reason the provision of information appeared to have mixed effects across studies in our review may be that customers often arrive at food outlets with pre-established order intentions; therefore, material to highlight new menu options and point-of-sale nutrition information may have a limited effect⁽⁴⁷⁾. Additionally, nutrition labels may be ignored if the main eating motivation is hedonic and quick decisions are required⁽⁵²⁾. Indeed, research shows that taste is valued more strongly than health for restaurant meals⁽⁵³⁾. Therefore, intervening to encourage healthier eating may be particularly challenging in these settings.

The studies that reported intervention fidelity found compliance to be moderate to high. However, engagement varied both between intervention venues and different intervention components, highlighting the need for a tailored approach. The relatively flexible format of some interventions – for example, where restaurants were given some liberty to choose which changes they would like to implement or adapt – meant that restaurants were able to select changes that best fit their context. Studies also reported that it is easier to engage participating businesses with interventions that are low-cost, low-effort and unlikely to be rejected or noticed by customers^(39,42) , and one intervention reported success using a staggered approach that slowly introduced more intrusive components^(44,45) . Whilst rare, some higher-level interventions were identified, demonstrating these can be implemented. However, higher-level interventions requiring structural changes may be beyond the financial resources of small restaurants and takeaways. One strategy could be creating greater and equal opportunity for small restaurants and takeaways to access and serve healthier foods, which are often more expensive or only come in large package sizes unsuitable (and unaffordable) for small businesses⁽¹¹⁾, for example, through the provision of wholesaler subsidies for healthy foods for small restaurants and takeaways. An intervention providing discounts on healthy foods for small stores at wholesalers found this led to increased availability of healthier options⁽⁵⁴⁾.

Economic incentives or perceived economic viability of interventions was a main facilitator for engagement. Additionally, establishing rapport with owners may benefit recruitment^(44,45) , a finding corroborated by previous evidence stressing the need for community outreach⁽¹¹⁾. Although studies reported which stakeholders were involved in the intervention in their backgrounds and methods, there was a lack of discussion and identification of the roles and benefits that other stakeholders played. Greater information about motivations and barriers to stakeholder involvement could improve the design and delivery of interventions in the future.

Implications for policy and research

Most studies relied on descriptive statistics and short follow-up periods and had no control or comparator sites, likely partly due to resource constraints and recruitment difficulties. More high-quality studies of interventions are needed, evaluating the longer-term impacts and sustainability of interventions using objective measures of outcomes (e.g. sales data). Investing in a new data system, or training staff on how to input data so that it is usable for the study, is advised if possible within resources available – improved sales data may also help inform businesses’ strategies, as well as be beneficial for researchers. Additionally, none of the interventions evaluated cost-effectiveness (see also (15)). Making the best use of available resources is crucial considering the economic constraints of many small restaurants and takeaways. Whilst none of the included studies mentioned that any of the included restaurants and takeaways offered online food deliveries, if online deliveries are offered, this could limit the exposure to some intervention components, particularly marketing materials in-store. Given the growing size of the online food delivery sector⁽⁵⁵⁾, future interventions and research should consider the interaction between in-store and the growing online food delivery market.

Policymakers who want to work with small restaurants and takeaways should be mindful of potential resource constraints and adopt flexible approaches with scope for restaurants to tailor interventions to their needs. Partnering with other stakeholders such as local business associations as well as building rapport with restaurant owners can facilitate recruitment. In addition to drawing on the findings from our review that has systematically appraised the evidence base of interventions in small restaurants, policymakers who want to work with small businesses to make healthier changes should consider recommendations from existing toolkits on how to work with small, independent restaurants and takeaways^(11,56) .

The majority of the interventions included in this review were conducted in areas broadly described as low-income or spanning multiple areas of deprivation. However, there was very little reporting on the impact the interventions may have had on reducing health inequalities. Most intervention elements were classed as belonging to the lower levels of the Nuffield ladder that are seen as less intrusive and require more agency and therefore are less likely to reduce health inequalities. In the future, researchers should consider reporting on neighbourhood levels of deprivation or collecting consumer demographic information to better assess how the interventions of interest might impact health inequities.

Conclusion

Interventions to encourage healthy eating in small, independent or local restaurants and hot food takeaways report mostly limited positive effects. The thirteen included interventions reflect a narrow set of countries (conducted in the USA or the UK) and over the past 20 years (published between 2004 and 2020). Most interventions used less intrusive strategies (e.g. providing information, enabling choice), although we found that more intrusive interventions can be acceptable to business owners if they are inexpensive, low-effort and not perceived as threatening customer satisfaction. Almost all interventions targeted the behaviour of both customers (e.g. menu labelling) and restaurant staff (e.g. cooking practices). However, the small number and poor quality of included studies hinder inference. More high-quality studies of interventions with objective purchase and consumption measures are needed to inform substantive policy-led actions.