From Plate to Planet: A Systematic Review and Meta-Analysis on Strategies to Reduce Plate Food Waste at Food Services

Abstract

Annually, over 931 million tons of plate food waste is generated in food services, affecting various aspects of sustainability. Therefore, this review aims to evaluate the most effective strategies or actions to reduce plate food waste. A systematic review and meta-analysis were conducted following a PROSPERO-registered protocol [#CRD42024501971], searching multiple databases and gray literature until August 2024. Studies evaluating strategies and actions against waste in various food services [restaurants, institutional services in hospitals, childcare centers, schools, universities, or businesses] were included, with no language, location, or date restrictions. The risk of bias was assessed using JBI tools. A random-effects meta-analysis was performed in R (version 4.2.1), with subgroup analyses based on intervention type, food service type, meal type, management, and distribution systems. Of the 6070 studies, 18 were included in the narrative synthesis and 6 in the meta-analysis. The most effective strategies or actions targeted clients (vs. employees), meals on plates (vs. trays), school canteens (vs. other services), self-managed establishments (vs. outsourced), and à la carte services (vs. self-service). In this sense, strategies focusing on clients, plate-served meals, school canteens, self-management, and à la carte services are more effective in reducing food waste. Further actions are needed in other areas like customers, trays, different kitchen types, outsourced services, and self-service menus.

1. Introduction

Sustainability refers to balancing economic development with natural resource preservation, ensuring progress for both current and future generations [1,2]. According to the 1987 Brundtland Report, sustainable development meets today’s needs without compromising future needs across five dimensions: social, economic, ecological, spatial, and cultural. In alignment with these principles, the UN Sustainable Development Goals (SDGs) [3,4] outline objectives such as eradicating poverty, reducing inequality, promoting sustainable economic growth, addressing climate change, and conserving natural ecosystems, aiming for global peace and prosperity by 2030. More than just promoting sustainability in collective food production, the goal is to avoid compromising future generations.

Food waste presents a significant social, environmental, and economic challenge, with global costs estimated at USD 2.65 billion annually [5,6,7,8]. The 2024 Food Waste Index Report highlights food waste as a market inefficiency, with over USD 1 trillion in food discarded each year [9]. Beyond financial losses, mathematical models suggest that reallocating wasted food could alleviate global hunger and promote sustainability [10,11].

Food waste occurs at various stages of the food production chain, particularly in food services. Significant losses happen during transportation, before food even reaches production facilities [1,2,9]. Once at the service location, additional waste can arise during storage, pre-preparation, and food preparation, often due to structural kitchen issues and food quality [3]. Plate food waste, or the uneaten portions left by diners, is another major contributor. It can be quantified by comparing the amount left on plates to what was served, known as the plate food waste–ingestion ratio, or measured per capita based on waste per meal served [12,13,14].

Efforts to control plate food waste focus on matching portion sizes to consumption patterns and ensuring menu acceptance. The literature suggests that a 10% limit for plate waste is the maximum acceptable in healthy communities, with 15–45 g per person considered an acceptable range [15]. However, this scenario can still reflect significant waste depending on meal volumes [16,17].

Food and nutrition education plays a key role in reducing waste. This multidisciplinary field promotes healthy eating habits through ongoing education for both food service employees and diners [18]. For specific contexts such as hospital food service, studies point to the relationship between higher food waste and the lack of coordination between professionals from external sectors and food service managers, as well as patients’ food preferences. These results demonstrate the importance of adjusting the service model to improve sustainability and operational efficiency [19]. Research indicates that employee training in portioning and menu planning, along with diner awareness, can reduce plate waste [20,21]. However, the best strategy or action for reducing this waste is still unknown.

In addition to assessing the quality of service concerning food waste in food service establishments, it is crucial to emphasize the optimization of food utilization practices, particularly in light of the growing global challenge of food, nutritional, and sustainable resource insecurity [22]. Conducting syntheses on food waste is crucial for providing a comprehensive and critical overview of the magnitude of the issue and its social, economic, and environmental implications. By compiling and analyzing existing studies, it is possible to identify knowledge gaps, best practices, and effective strategies to reduce losses across various stages, such as food production, distribution, and consumption. Additionally, a synthesis facilitates the dissemination of scientific evidence that can inform public policies and guide interventions in food services, promoting greater efficiency in resource use and contributing to global food security and nutrition. Therefore, given the negative impact of food waste on sustainability and the significant waste generated by food services, this systematic review and meta-analysis aimed to identify the most effective strategies for reducing plate food waste in food services.

2. Materials and Methods

This systematic review and meta-analysis followed the recommendations of the Cochrane Guideline for Systematic Reviews of Interventions [23] and was conducted according to the PRISMA checklist [24]. The protocol was previously registered on the PROSPERO platform under the code CRD42024501971.

2.1. Search Strategy

We searched for studies in ten independent electronic databases: MEDLINE (by PubMed), Embase, CENTRAL (by Cochrane Library) and Spanish Bibliographic Index in Health Sciences (IBECS), Bibliografía Nacional en Ciencias de la Salud Argentina (BINACIS), Nursing Database (BDENF), Committee on Undergraduate Medical Education (CUMED), Base de Datos Nacional del Paraguay (BDNPAR), Revista Argentina de Salud Pública (ARGMSAL), Sustainable Development Goals (SDGs), Web of Science, and Eurostat from inception until August, 2024. Additionally, we manually searched for observational or interventional studies using the references of the selected studies as a sample.

There were no restrictions on the language, date, document type, or publication status for record inclusion. Descriptors were identified in the Medical Subject Headings, Health Sciences Descriptors, and EMBASE Subject Headings (Emtree). Subsequently, the descriptors were combined with the Boolean operator AND, while their synonyms were combined with the Boolean operator OR. The search strategies adopted in each database are presented in the Supplementary Material (Table S1).

2.2. Outcomes

The primary outcomes were mean plate food waste (or leftover food intake, following Equations (1) and (2) [16], measured in mean kg of food weighed after disposal [25].

$$\% plate food waste={\displaystyle \frac{weight of plate food waste\times 100}{weight of meal distributed}}$$

(1)

$$Per plate food waste \left(kg\right)={\displaystyle \frac{weight of plate food waste \left(kg\right)}{number of served meals}}$$

(2)

To eliminate the fact that the reduction in absolute food waste values was associated with a reduction in the number of diners (and, consequently, meals), after the interventions, we calculated the per capita food waste values according to Equation (2).

2.3. Intervention

An intervention was considered to be any action or strategy in food and nutrition education used to reduce food waste, such as awareness-raising and educational campaigns with posters and banners, distribution of leaflets, menu planning, and training of food handlers. In food services, interventions for reducing food waste (plate food waste per capita) include educational campaigns about portion control and use menus that help diners make informed choices, as well as strategies involving training on efficient food preparation, better portion control, and improved food-handling practices.

To better understand the quality and effectiveness of the intervention, only studies that included data before and after the campaigns and actions in nutrition were analyzed.

2.4. Eligibility Criteria

Observational studies (cross-sectional, case–control, or cohort studies) and intervention studies carried out in food services (restaurants and institutional services in hospitals, nurseries, schools, universities, or companies) that analyzed plate food waste before and after actions or strategies to reduce it were included. Studies carried out in hotels were excluded (due to the dynamics of production not being similar to other food service categories), as were experimental studies, case series or case reports, trials, reviews, in vitro or experimental animal studies, cost-effectiveness analyses, letters, comments, and editorials.

2.5. Study Selection and Data Extraction

The studies found in the electronic database search were exported in ‘ris’ format to the Rayyan Qatar Computing Research Institute application for systematic reviews [26]. Two reviewers (NSG and MGR) independently and blindly assessed the titles and abstracts. After this stage, the textual analysis of the studies was carried out independently. The third reviewer (FEMJ) analyzed any discrepancies.

The following information was collected for the extraction table: reference (author, year), title, location, study design, follow-up period (weeks), food service characteristics (type of food service, type of diners, distribution method, and system), number of meals served, definition and total in kilograms of plate food waste, and strategy and/or action used to reduce food waste in the food service and the main results.

2.6. Risk of Bias Evaluation

The Joanna Briggs Institute (JBI) instrument was used to assess the risk of bias in studies [27]. Two reviewers (NSG and MGR) independently and blindly assessed the risk of bias. The third reviewer (FEMJ) analyzed any discrepancies. Studies were classified as low risk of bias if the total score was up to 49.0%, moderate risk of bias between 50.0% and 70.0%, and high risk of bias if it was above 70.0% [28] (Supplementary Material Table S3).

2.7. Meta-Analysis

A random-effects meta-analysis model was used to combine studies and calculate the mean difference in food plate waste as percentage and kg [29]. Subgroup analysis was carried out by type of intervention, distribution, food service type, type of meal, management modality, and distribution system. Heterogeneity was assessed using the random effects model; the chi-squared test was applied with a significance of p < 0.10, and its magnitude was determined using the I-squared (I²) test.

In all analyses, a p-value < 0.05 was considered statistically significant. Publication bias analysis was not performed, as this measure is inappropriate for prevalence meta-analysis [30]. The analyses were carried out in R.Studio software, version 4.2.1 (R: A Language and Environment for Statistical Computing, Vienna, Austria), using the ‘Meta’ packages, versions 5.0-0.

3. Results

The search process identified 4459 studies. After removing 200 duplicates, 4259 studies were screened based on titles and abstracts. Of these, 4158 were excluded, and 83 did not meet the eligibility criteria for full-text review, as detailed in the Supplementary Materials. Additionally, 14 gray literature studies were evaluated. In an updated search, 1583 studies were retrieved from the Web of Science and 28 from Eurostat (https://european-union.europa.eu/index_en, accessed on 17 September 2024), though no new studies met the eligibility criteria. Overall, the search strategy yielded 6070 studies. From these, 18 were included in the narrative review, and 6 were incorporated into the meta-analysis (Supplementary Material Table S2) (Figure 1).

3.1. Studies Characteristics

Out of the 18 studies eligible for this systematic review, 6 were included in the meta-analysis [

Table 1. Characteristics of the studies included in the systematic review.

Reference	Study Location	Food Service Type	Type of Consumers	Type of Intervention	Type of Utensil Used	Management Modality	Distribution System	Portioning by Employees (Description)	Payment
Bicalho et al., 2013 [31] *	Brazil	University Restaurants	NI	Educational activities for employees	Plates	NI	Self-service	No	NI
Borges et al., 2019 [32] *	Brazil	University Restaurants	Clients and employees	Educational activities for employees	Plates	Contracted out	Self-service and Assisted Service	Yes, just the protein dish and a dessert	NI
Buzatti et al., 2015 [33]	Brazil	Popular Restaurant	NI	Educational activities for clients	NI	NI	NI	NI	NI
Carrijo et al., 2020 [34]	Brazil	NI	NI	Educational activities for clients	Trays	NI	NI	NI	NI
Chaves et al., 2019 [20] *	Brazil	Hospital Restaurants	Employees	Educational activities for clients	Plates	NI	Self-service	No	NI
Delazeri et al., 2015 [35]	Brazil	Restaurants	NI	Educational activities for clients	Trays	NI	Self-service	Yes, just dessert	Price per person
Machado et al., 2014 [36] *	Brazil	Restaurants	Employees	Educational activities for clients	Plates	NI	NI	NI	NI
Malefors et al., 2022 (1) [37]	Sweden	School Canteens	Clients and employees	NI	NI	NI	NI	NI	NI
Malefors et al., 2022 (2) [38]	Sweden	School Canteens	Clients	Educational activities for clients	NI	Self-management	NI	NI	NI
Malefors et al., 2024 [39]	Suécia	School Canteens	Clients	NI	Plates	NI	NI	NI	NI
Quemelli et al., 2020 [40]	Brazil	Hospital Restaurants	NI	Educational activities for clients and employees	Plates	Contracted out	Self-service and Assisted Service	Yes, just the protein dish and a garnish	Price per person
Rabelo et al., 2022 [21]	Brazil	University Restaurants	Clients and employees	Educational activities for clients	Plates	Self-management	Self-service and Assisted Service	Yes, just the protein dish, the dessert, and the portioned juice	NI
Scholz et al., 2019 [19] *	Brazil	Restaurants	Employees	Educational activities for clients	Trays	Contracted out	Self-service	No	NI
Silva et al., 2010 [41]	Brazil	Hospital Restaurants	Employees	Educational activities for clients	Trays	Self-management	Self-service	No	NI
Souza et al., 2019 [42] *	Brazil	School Canteens	Clients and employees	Educational activities for employees	Plates	Self-management	À la carte	Yes, the whole dish has been portioned	NI
Thiagarajah et al., 2013 [43]	USA	University Restaurants	Clients and employees	Educational activities for clients	Plates	Self-management	Self-service	No	Price per person
Viana et al., 2016 [44]	Brazil	Hospital Restaurants	Clients and employees	Educational activities for clients	Plates	NI	Self-service	No	NI
Vidal-Mones et al., 2022 [45]	Spain	School Canteens	Clients	NI	Plates	Self-management	Self-service and Assisted Service	Yes, just dessert	NI

NI = Not informed; * Studies that were included in the meta-analysis.

]. The remaining studies were excluded from the meta-analysis due to incomplete data on plate food waste (kg) before and after interventions. In terms of study design, 10 (55.5%) were cohort studies, 4 (22.2%) were cross-sectional, 2 (11.1%) were case studies, 1 (5.5%) was a case–control, and 1 (5.5%) was a quasi-experimental study. Geographically, 72.2% (n = 13) of the studies were conducted in Brazil, 16.6% (n = 3) were conducted in Sweden, 5.5% (n = 1) were conducted in the USA, and 5.5% (n = 1) were conducted in Spain.

3.2. Meta-Analysis Results

The meta-analysis included six studies, with meal evaluations summarized in

Table 2. Plate food waste before and after intervention for their reduction in food services.

	Before Intervention		After Intervention
Reference	Meal (Absolute Number)	Plate Food Waste (kg)	Meal (Absolute Number)	Plate Food Waste (kg)
Bicalho et al., 2013 [31]	193	12.58 ± 2.68	300	14.64 ± 2.56
Souza et al., 2019 [42]	45	2.16 ± 0.45	45	1.68 ± 0.71
Borges et al., 2019 [32]	1150	54.20 ± 11.75	1241	46.79 ± 11.46
Chaves et al., 2019 [20]	152	6.80 ± 2.02	158	6.40 ± 2.39
Machado et al., 2014 [36]	1350	82.20 ± 14.40	1349	74.0 ± 13.1
Scholz et al., 2019 [19]	4588	5.46 ± 0.60	4229	4.93 ± 1.22
Total	7478	27.23 ± 7.29	7322	24.74 ± 7.01

. A total of 7478 meals were assessed before the implementation of waste-reduction strategies, and 7322 meals were assessed afterward. Client-focused strategies (MD = 3.02) led to a greater reduction in plate waste compared to employee-focused educational strategies (MD = 1.93), although this difference was not statistically significant (Figure 2).

Regarding meal distribution utensils, services using plates (n = 5) achieved better waste-reduction results than those using trays (n = 1) (Figure 3). Among food service types, school canteens demonstrated a significant decrease in food waste following intervention strategies, a result not seen in universities, hospitals, or commercial restaurants (Figure 4).

In terms of management, self-managed restaurants achieved better per capita waste reduction than outsourced services (Figure 5). Lastly, food services using the plating system showed greater waste reduction compared to those using self-service (Figure 6). The most effective strategies observed in this study are summarized in Figure 7.

4. Discussion

The discussion of the results of this review was organized into the following topics: (a) the importance and implications of the results, in which each result found [with or without statistical significance by the meta-analysis] was discussed; (b) limitations and strengths, in which we point out the main limitations and strengths of the results found.

• Importance and implications of the Results

This systematic review and meta-analysis offer a detailed overview of the impact of educational interventions and strategies targeting employees and customers in food services to address plate food waste. The most effective approaches focus on client-targeted initiatives, using plates instead of trays, implementing measures in school cafeterias, adopting self-managed operations, and offering à la carte services rather than self-service. These strategies have shown greater success in reducing per capita food waste by influencing consumer behavior and improving food service efficiency. Customers-centered actions, such as awareness campaigns and portion adjustments, encourage more mindful food choices helping to limit waste. Plates, compared to trays, reduce the amount of food served at once, minimizing leftovers. In school cafeterias, where eating habits are shaped, nutritional education can foster long-term sustainable behavior. Self-managed establishments offer more flexibility in tailoring waste-reduction practices to consumer needs and operational control, unlike outsourced services, where the emphasis is often on efficiency and profit.

Adapting these strategies to other contexts—such as high-production kitchens, outsourced services, and self-service environments—requires careful consideration. In large kitchens, investment in waste-tracking technologies [46] and continuous staff training may be necessary [47]. Outsourced services should include waste-reduction incentives in contracts, not just cost efficiency. In self-service settings, smaller portion sizes and educational signage can help reduce food waste. Tailoring interventions to the specific needs of each environment is key to achieving more sustainable and efficient food systems.

Primary studies have pointed to the relationship between the successful implementation of actions and waste reduction in different food services. Strotmann et al. (2017) [15] found that strategies aimed at employees and designed with participatory approaches, such as workshops and focus groups, significantly reduced the average waste rate in hospital food services. In commercial all-you-can-eat food services, Ravandi and Jovanovic (2019) [48] identified that reducing the size of dishes reduced food waste by up to 30% without affecting the quality of the service. This strategy is reaffirmed by Richardson et al. (2021) [49], in which reducing the size and changing the shape of the plate from round to oval reduced waste by approximately 4% in university restaurants that use all-you-can-eat service. Still focusing on the customer, Whitehair et al. (2013) [47] showed that strategies aimed at behavior, specifically simple to-the-point prompt-type messages, effectively reduced food waste by 15%.In this review, it was observed that food waste reduction was more effective when served on plates than on trays. This result is associated with the volume of food on trays and its poorer presentation, reducing food acceptance [50].

Greater effectiveness of actions to reduce food waste was also observed in university restaurants compared to other types of food service. Universities are considered strategic environments for raising health awareness and promoting better habits [51]. Self-managed establishments were more effective at reducing food waste than outsourced establishments.

In the self-management model, the institutions themselves, whether public or private (e.g., schools, universities, health services, prisons, and companies), are responsible for all the management of meal production, including hiring labor, purchasing equipment and raw materials, and producing and distributing the meals [52]. It is important to highlight whether the customer pays for their own meal and what distribution system is used, as these factors directly influence consumer behavior and the amount of food waste. When customers pay for their meals, they tend to be more conscious about what they choose and how much food they serve, resulting in less waste. On the other hand, in environments where meals are free or subsidized, consumers may not feel as compelled to avoid waste. Additionally, the meal-distribution system, such as à la carte service versus self-service, also impacts waste. À la carte service, where the establishment controls portions, can help limit excess food and, consequently, waste. In self-service systems, where customers serve themselves, they commonly take more than they can consume, especially if the cost is not directly proportional to the amount of food served.

In this model, the production of meals is not the end activity, so there is no direct profit from this production. On the other hand, food services that adopt the outsourcing modality are managed by companies that specialize in the food industry, which produce meals as their core activity and thus market the meal itself or the meal-production service [53,54]. There is a scarcity of studies investigating the impact of the food service management model on food waste, especially using the plate food waste per capita indicator. In self-management, as there is no direct profit from the sale of meals, the service provided from the point of view of the menu quality can be superior to the service provided by outsourced companies, depending on the contract that governs the outsourced service. The need to contain costs in outsourced services to guarantee the planned profit margin can lead to a reduction in the quality of the meal served and in the service provided, which can translate into greater customer dissatisfaction with the meal and, consequently, higher per capita plate food waste. Toscano et al. (2018) found a difference in the approach to criteria for selecting raw material suppliers in food services [54]. While in self-managed services, the emphasis was on the supplier’s quality and suitability, in outsourced services, price was considered the most relevant. The quality of the outsourced service can also be affected by the precarious nature of the work. Cardoso, Feitosa, and Calazans (2018) point out that outsourced services are often characterized by employees with low levels of training and high turnover [55]. Rossi et al. (2017) found that employees of self-managed food services had three times more food safety training than outsourced companies, suggesting that self-managed companies generally invest more in their workers with structured training programs [56].

Better results were also observed in à la carte food services compared to self-service. In à la carte distribution, the employee’s control of the quantity to be served can prevent the diner from serving larger quantities and, consequently, waste. However, as there is no autonomy for the diners to serve themselves, there is a possibility that the portion served will be larger than the desired amount. In this case, adapting the portion to the food service audience can be an important strategy for reducing per capita waste [57,58,59]. For portion reduction to be effective as an intervention for food waste, establishment staff must be adequately trained.

b.

Limitations and Strengths

One limitation of this systematic review is the lack of sufficient information to establish a theoretical framework for the causes of high plate food waste (rest-ingestion). This gap makes it difficult to fully assess the effectiveness of the interventions, as the underlying causes remain unclear and thus incomparable. More research is needed to better understand the factors contributing to plate food waste, allowing researchers, nutritionists, and entrepreneurs to create more effective, context-specific interventions. Additionally, 72.2% of the studies included were conducted in Brazil, limiting the generalizability of the findings to other regions with different cultural, economic, and operational contexts. Another notable limitation is the lack of focus on customer-oriented interventions despite the significant influence of customer behavior on food waste. Addressing this gap could offer a more balanced perspective. Finally, the scarcity of intervention studies in the existing literature may weaken the findings regarding controlled scenarios.

Despite its limitations, the current study has several positive features (strengths): a rigorous methodology was used based on the PRISMA guidelines; a comprehensive literature search included 12 independent databases; search, selection, and data extraction applied to the selected studies were performed separately, and in duplicate and extraction data of electronic database, by two researchers; and a third party was used to resolve disagreements.

5. Conclusions

Our findings are based on the analysis of 18 studies included in the narrative review and 6 studies that could be incorporated into the meta-analysis due to incomplete data on plate food waste before and after interventions. In food services, the most effective interventions for reducing food waste (plate food waste per capita) were aimed at clients [educational campaigns about portion control and use of menus that help them make informed choices], meals served on plates, actions in school canteens, actions realized in self-management food service, and à la carte food services. Based on the results of this study, we suggest effective strategies to be used in food services. However, we reinforce the importance of conducting studies that cover more food services and other waste mitigation strategies. Therefore, more in-depth actions are needed for other areas, such as clients using trays, different types of production kitchens, outsourced establishments, and self-service menu settings. For these areas, interventions could focus on optimizing food-distribution methods, enhancing staff training, and implementing more robust waste-tracking and -management systems.