The Measurement of Food Insecurity in High-Income Countries: A Scoping Review

The measurement of food insecurity is essential to monitor the prevalence, risk factors, consequences and effects of food insecurity and the interventions and policies implemented to tackle it. Yet, how best to apply it remains an unsettled issue due to the multifaceted and context-dependent nature of food insecurity. We report a scoping review of measures of food insecurity at the individual and household level in high-income countries with the final purpose of facilitating a catalogue of instruments to be used by both researchers and practitioners. The scoping review was conducted following the methodological framework of Arksey and O’Malley and the Joanna Briggs Institute guidelines. We included all types of documents published between 2000–2020 using instruments that estimate food insecurity at both individual and household level in high-income countries, and with respondents including adolescents, adults, and elderly. We identified a total of 23 measurement strategies being used in 33 peer-reviewed publications and 114 documents from the grey literature. Our results show that most measures focus on the access dimension of food insecurity and that further research is required to develop measures that incorporate aspects of quality of dietary intake and relevant individual, household and social conditions related to food insecurity.


Introduction
The 2020 edition of the Food and Agriculture Organization's (FAO) yearly report "The State of Food Security and Nutrition in the World (SOFI)" showed that food insecurity was rising. Worldwide, it was estimated that in 2019, 750 million people (9.7%) were exposed to severe levels of food insecurity and more than 3 billion people could not afford a healthy diet as a consequence of conflict and civil strife, climate variability, economic crisis, and persistent poverty and inequality [1]. The COVID-19 situation has added a further threat to food security across the globe, as a result of which 148 million additional people became severely food insecure [2]. According to the same report, less than 2.5% of the population in Europe and North America would be in this situation, but moderate and severe food insecurity levels have risen to almost 9%, getting closer to 2014 levels. More localized analysis shows that prevalences of food insecurity in specific populations of these territories could be above 10-15% [3][4][5][6].
Food insecurity threatens both individuals and societies, and constitutes a serious threat to public health and wider society [7]. In children, it has been associated with impaired physical and psychological development, the effects of which can persist into adolescence and adulthood. In adults, characteristic conditions of the double burden of diseases have been observed, such as the combination of nutritional deficiencies (i.e., anemia) and excess-diseases (i.e., diabetes, obesity). In addition, food insecurity can result in psychological burden and social stigma [8,9], and can also have socioeconomic spillovers in terms of productivity and health-care expenditure. People's experiences and how they cope with food insecurity have been extensively studied and documented by sociologists and anthropologists, and have considerably influenced our comprehension of what food insecurity entails [10,11] The concept, interest in and understanding of food insecurity has evolved since it was first coined by the World Bank as a notion designated to broaden the understanding of hunger. The first definition of food security, "access by all people at all times to enough food for an active, healthy life" [12], was expanded ten years later in the World Food Summit to include recognition of the multidimensionality of the concept. Since then, food security is mostly referred to as the situation in which "all people at all times have physical, economic and social access to sufficient, safe and nutritious food to maintain a healthy and active life" [13]. Additionally, the Committee on World Food Security added in 2012 that 'it is supported by an environment of adequate sanitation, health services and care, allowing for a healthy and active life' [14], something that has been proven crucial [15].
The interest in hunger and food insecurity was initially in low-income (then referred to as developing) countries. However, it gathered momentum in high-income (developed) countries thanks to Kathy Radimer's seminal work at Cornell University [16], where she explored the phenomena and experiences of food insecurity in the US. Drawing on her findings and those of other scholars, the USDA adopted "the limited or uncertain availability of nutritionally adequate and safe foods, or limited or uncertain ability to acquire acceptable foods in socially acceptable ways" [17] as the definition of food insecurity, incorporating elements of contextualization to the definition of food (in)security, e.g., what is acceptable in one sociocultural environment may not be in another.
These remarks on the definitions are significant since the measurement of food insecurity draws on them. As mentioned, the definition provided by the FAO is the most commonly used and comprises of four dimensions that are necessary to achieve food security: availability, access, utilization and stability [18]. Availability refers to the supplies that are sourced for individuals to cover their dietary needs. Therefore, it is determined by food production, stock levels and net trade, and generally considered at the country-level and assessed through balance sheets. Access concerns how individuals reach the food available in their environment and is in turn conditioned by physical (i.e., transportation) and economic (i.e., prices, incomes) constraints. It is normally assessed at the household or individual level, and three domains of inadequate household-level food access are distinguished: quantity, quality and the psychological effects of inadequate quantity or quality food supply [19]. Utilization involves ensuring proper nutrition for the organism, and comprises elements such as intra-household distribution, purchase and conservation practices, food preparation, etc. As such, its measurement is generally done at the individual level. In order to achieve food security, all the former dimensions need to occur simultaneously and be stable over time. In high-income countries, the biggest constraint is found in the access dimension, and it is typically addressed through social wages, food banks, and soup kitchens [20].
The measurement of food insecurity is essential to monitor the prevalence, risk factors, consequences and effects of food insecurity and the interventions and policies implemented to tackle it. Yet, how best to apply it remains an unsettled issue mainly due to the multifaceted and context-dependent nature of food insecurity [16,19,21,22]. In recent years, several reviews of food insecurity measurement in high-income countries have been published in the literature [16,[21][22][23][24][25][26][27][28]. With some differences in the objective of their study, databases and date of the search, as well as data retrieved, their results show how currently food insecurity is mostly assessed through multiple item questionnaires. However, these can be long, burdensome to respond and costly to implement. Moreover, most measures evaluate the access dimension of food insecurity and do not adequately capture its psychological and quality domains, nor the experience of or consequences for individuals. An additional question refers to the appropriateness of using tools developed for low-and middle-income countries in high-income ones, and vice versa. In view of the alarming rates of food insecurity in high-income countries, it is necessary to identify the most adequate tools to measure it, considering the nature, characteristics, and requirements of food insecurity in these contexts.
We aim at complementing and expanding these former works through a scoping review of measures of food insecurity at the individual and household level in high-income countries, which will also include the grey literature, with the final purpose of facilitating a catalogue of instruments to be used by both researchers and practitioners.
Hence, this review delves into the various types of tools that have been employed to measure food insecurity in high-income countries at the individual and household level, focusing on the following research questions: (i) What are the existent instruments available to measure food insecurity in individuals and households in high-income countries? (ii) What dimensions of food insecurity are the ones more often included and the ones that are missing? (iii) What are the typical characteristics of the instrument?, i.e., scale's origin (country, institution, and language), number of items, types of response options, psychometric features of the instrument, focus on quantity or/and quality of food, number of articles using the particular instrument, etc.? (iv) What are the differences in the measures used for different target groups based on age, i.e., adolescents, adults and elderly?

Materials and Methods
This review was conducted following the methodological framework of Arksey and O'Malley [29] and the Joanna Briggs Institute guidelines [30]. These frameworks involve key phases which include identifying the research question; identifying relevant studies; study selection; charting data; and finally collating, summarizing, and reporting results. In this case, we have not pursued the sixth phase of stakeholder consultation. Consequently, the Guidelines published by the Joanna Briggs Institute as well as the Preferred Reporting Items for scoping reviews (PRISMA-ScR) and the Preferred Reporting Items for Systematic Reviews and Meta-analysis Protocols Statement (PRISMA-P) have been also followed [31,32].

Eligibility Criteria, Information Sources and Search Strategy
The eligibility criteria include the following: (i) original studies, review articles, food aid and food insecurity reports published in peer reviewed journals as well as the grey literature-which include reports and statistics from government sources and NGOs, dissertations or theses, conferences and presentations, and newsletters and press articlesreporting to have used (ii) instruments that estimate food insecurity in adults at both individual and household level (iii) in high-income countries according to the World Bank [33] and with (iv) respondents including adolescents, adults and elderly. Papers reporting food insecurity prevalence or its health effects in children were excluded. No language restrictions were established, and the timeframe for inclusion was 2000-2020.
The search strategy for information sources was devised in consultation with an academic librarian along with two members of the research team with expertise in review methodology. The algorithms for search strategy focused on title, keywords and abstract. Key words included: "food insecurity", "food security", "dietary diversity", "food insufficiency", "food poverty", "measurement" OR "measure", "instrument", "scale", "questionnaire", "high-income countries", "developed countries", "individual", "household" ( . . . .). Specific searches for each database can be found in Supplementary Materials File S1.
For the peer-reviewed literature, the following medical and social science bibliographic databases were searched: Cochrane Central Register of Controlled Trials (CENTRAL), Medline (PubMed), Embase, CINAHL, FSTA, PsycINFO, Scopus, Sociological Abstracts and Web of Science Core Collection. The reference list of the eligible papers was scanned for additional registries.
The search for the grey literature was conducted by two research team members. Since there is not yet a gold standard for the grey literature, the search was carried out mainly via search engines such as Google, Google Scholar and OpenGray. Specific steps and recommended resources for searching the grey literature were followed [34]. To ensure that a large amount of the of grey literature was included, the search was also extended to specific websites which provided information on food insecurity such as FAO, USDA, UNICEF, WHO, etc. In addition, top university websites of the world offering a comprehensive list of grey literature databases such as DOAR, ELDIS, Factiva, periodicals index online were also searched.

Study Selection
For the screening and final selection of peer-reviewed journals, the software tool COVIDence was employed. This included uploading the peer-reviewed journals along with the full texts on COVIDence. Based on the suggestions of Arskey and O'Malley, the identification and selection of studies were a comprehensive and iterative process, which included weekly meetings in order to discuss the different phases and improve and direct the diverse aspects under agreement. Firstly, four research team members independently screened the titles and abstracts of the studies based on the eligibility criteria of this review. Based on a consensus, those documents which did not meet the eligibility criteria were eliminated from the study. Next, full texts of all potentially relevant documents were reviewed by the same four reviewers. Based on the consensus, few papers were eliminated. The process was reported following a flow chart from the extension for Scoping Reviews (PRISMA-ScR) [31], as shown in Figure 1.

Data Charting
Data were extracted, by pairs, by four members of the research team, and compared. A standardized form created by the research team was employed to input the data into Microsoft Excel Spreadsheets which was, based on the iterative process described above, continuously updated throughout the search strategy.
The data extracted for the peer-reviewed and grey literature was based on the following: title, author, year of publication, journal; country of development of the study; specific food insecurity indicator or indicators used; study population characteristics (age, country, household or individuals, respondents); procedure of data collection in the study (only in the peer-reviewed literature); results of the study.

Analysis of Results
The main findings were summarized using a narrative descriptive synthesis approach. A table containing relevant information about the different food insecurity measurement tools extracted from the selected peer-reviewed journals and grey literature of this review was completed, containing the name of the food insecurity instrument, its author/s and year; languages in which the instrument has been developed/translated; original purpose of development; unit to collect food insecurity data, i.e., individual or household; reference period of the assessment of food insecurity; dimensions of food insecurity; number of items; psychometric properties; types of response options and food insecurity classification; focus on quality and/or quantity of food intake; references in the review that have employed this particular instrument along with the country and level of food insecurity (individualhousehold); and strengths and limitations of this instrument. Data regarding the strengths and limitations of the instruments were retrieved from the documents using them as well as the documents reporting the creation and/or validation of their own measures.

Results
We initially identified 246 records-132 from the scientific literature and 114 from the grey literature. After removing duplicates and irrelevant studies from the scientific literature, 240 documents (126 from peer reviewed journals, 114 from the grey literature) were moved to the screening phase. Title and abstract screening eliminated 77 documents from the peer-reviewed literature. Afterwards, the remaining 55 records were assessed for eligibility using full text. Finally, 33 publications from the scientific literature were included (Figure 1), which comprised original articles (n = 26), literature reviews (n = 7), and the 114 documents from the grey literature.
Overall, these 147 documents reported data on food insecurity at the household level and individual level in high-income countries using a total of 23 measurement strategies.
In this section, we first describe the overall characteristics of the studies reported in these documents, separating the scientific and grey literature, to subsequently proceed to the depiction of the 23 measurements found in our sample. Table 1 shows the basic data of the peer-reviewed literature included in this scoping review. Over 90% of the reviewed empirical studies were conducted after 2015 (only [35,36] were published before that date). Eleven papers reported data on more than one country, with six of them including global samples of more than 100 countries [37][38][39][40][41][42], while the others used data from Europe [43], Macedonia, Moldova and Romania [44], and a combination of US and Canada [45]. The rest of the the papers used samples based in one country: US [35,[46][47][48][49], Australia [50,51], Portugal [36,52], Canada [43,53,54], France [55], Greece [56], Italy [57], Norway [58] and Poland [59]. The remaining seven documents were literature reviews with no geographic restrictions, except for [60,61] which focused on combinations of US, Canada, England, New Zealand and Australia.
Instruments to assess household food insecurity included the 18-item Household Food Security Survey Module from USDA (18-HFSSM) [45,47,[53][54][55]65], the Brazilian Food Insecurity Scale [36,52], the Household Food Insecurity Access Scale [59], the Food Security Survey Module (FSSM) [56], the Food Insecurity Index (FII) [49], the Household Hunger Scale (HHS) [44], the Healthy Diets ASAP [51] and the European Quality of Life Survey item "could your household afford a meal with meat, chicken or fish every second day if you wanted it?" [43]. Food Insecurity at the individual level was measured through the Food Insecurity Experience Scale (FIES), mostly through the Gallup World Survey [37][38][39][40]42,62], the six or ten-item Household Food Security Survey Module from USDA (6-HFSSM; 10-HFSSM) [35,46,48], the 10-item Radimer-Cornell Scale [58], the Household Food Insecurity Access Scale (HFIAS) [57] and an ad hoc developed single-item measure [50]. Other scales identified by the review papers include the Community Childhood Hunger Identification Project (CCHIP), the single-item National Health and Nutrition Examination Survey (NHANES-III), the USDA Food Insufficiency Question, the 10-item AFSSM, adapted HFSSM, the Australian National Health Survey single-item measure, the Household Food and Nutrition Security Survey (HFNSS), the USDA Food Insecurity and Hunger Scale, the New Zealand measure of individual deprivation, the Hager 2-item Food Insecurity Screening Questions, the Girard four point tool, the Kuyper past food insecurity screening, the Townsend Food Behaviour Checklist and other multi or single item measures.
Of the original studies using primary data (not previously existing surveys), the vast majority collected food insecurity information in face-to-face interviews. The study by Koh et al. [46] also uses online data collection. In those papers based on data from the GWP, food insecurity instruments are administered either face-to-face or via telephone. Nettle and Bateson's [48] study also combines these two methods of data collection. Last, the procedure of data collection is not clearly stated for some studies, although is very likely that measurements have been taken in person [47,49,50,66,67]. The results suggest that the driver that could most mitigate women disadvantage is education: people with a university degree present a lower probability of experiencing food insecurity, both for men and for women. On the contrary, familial characteristics, such as the number of children in the household, present a higher impact on women's food insecurity than men. The incidence and degree of food insecurity was measured with the Household Food Insecurity Access Scale (HFIAS). The study found that about 43% of the respondents were exposed to food insecurity, including almost 9% to severe food insecurity, which is well above the average for the entire Polish population. By applying cross-tabulation and the zero-inflated Poisson regression model, the study found that the higher age and secondary or higher education of the farm manager, having children in the household and higher land productivity have a statistically significant negative influence on households' food insecurity (i.e., decreased HFIAS score). On the contrary, family size of five or more and production type "permanent crops" and "dairy cows" have a statistically significant positive influence on households' food insecurity (i.e., increased HFIAS score).  Hunger in South-eastern European families, among families with children showing elevated behavioral problems, was associated with more family violence, but specifically poorer mental health and less emotional support above and beyond socio-structural strains.
Adapting parenting interventions to support the primary caregiver in getting more access to emotional support may potentially also change hunger and its association with health and violence. However, this hypothetical pathway of change needs explicit testing (1) to examine macro-level prevalence of food insecurity among the elderly in 48 developed countries. (2) to assess possible risk factors affecting food insecurity by the elderly in developed countries, using cross-nationally comparative methods.

Individuals (elderly) Gallup survey
Food insecure individuals were more likely to live alone, not have a partner, and tended to have poorer scores for social support and wellbeing. Additionally, poor community infrastructure was associated with food insecurity of elderly people, and there were more food insecure elderly people in urban areas. At the multinational level, results indicated wide and statistically significant disparities among continents. The study concluded that not only personal factors but also social conditions could prevent the elderly from achieving full food security status. The aim of this research was to describe the apparent prevalence of food insecurity in adults at enrolment in a food literacy program and to examine the relationship between food insecurity and a range of independent variables.

Individuals
Individuals were encouraged where possible to complete a questionnaire before starting the first session The results are salient as they indicate an association between food literacy and food insecurity. The implications are that food insecure participants may respond differently to food literacy programs. It may be necessary to screen people enrolling in programs, tailor program content, and include comprehensive measures in evaluation to determine effect on the impact of food literacy programs on different subgroups

18-item HFSSM Canada
To assess whether Canadian households with children experienced reductions in food insecurity compared to those without following the roll-out of a new country-wide income transfer program: the Canada Child Benefit (CCB).

Households (adults and children)
NA Multinomial logistic regressions were used to test the association between CCB and food insecurity among three samples: households reporting any income (n = 41,455), the median income or less (n = 18,191) and the Low-Income Measure (LIM) or less (n = 7579). The prevalence and severity of food insecurity increased with economic vulnerability, and were both consistently higher among households with children. However, they also experienced significantly greater drops in the likelihood of experiencing severe food insecurity following CCB; most dramatically among those reporting the LIM or less (DID: −4.7%, 95% CI: −8.6, −0.7). These results suggest that CCB disproportionately benefited families most susceptible to food insecurity. Furthermore, our findings also indicate that food insecurity may be impacted by even modest changes to economic circumstance, speaking to the potential of income transfers to help people meet their basic needs. We aimed to deepen understanding of the relation between food insecurity and subjective well-being among countries from the perspective of possible hedonic adaptation between food insecurity and subjective well-being

Individuals Gallup survey
The prevalence of food insecurity was strongly and negatively associated with subjective well-being across 147 countries. The association between food insecurity and poor subjective well-being within countries was stronger for more-developed countries, providing evidence of hedonic adaptation between food insecurity and subjective well-being. Food insecurity explained substantial variation in subjective well-being both among and within countries Household interviews were conducted face-to-face in respondents' own homes using standardised question wording.
The article finds evidence to support both contentions: food insecurity has risen across many European countries and has varied by welfare regime. It also finds that contrary to expectations, the sharpest rise was in the Anglo-Saxon countries of Ireland and the UK, rather than Southern or Eastern European countries. Those experiencing food insecurity with hunger at baseline were more likely to improve food insecurity score than those who did not (OR = 3.51, 95%CI: 2.92-4.21). Households NA It first covers the methods used to measure food insecurity in the USA and Canada. In both countries, a series of 18 questions in the Core Food Security Module are used to identify whether a household is food insecure. It then briefly covers the current extent of food insecurity in each country along with some discussion of the recent history of food insecurity. A central advantage to using the Core Food Security Module in Europe is that the measure has been proven useful in other high-income countries, and using a standardized measure would allow for cross-country comparisons. I next cover two large-scale food assistance programs from the USA, the Supplemental Nutrition Assistance Program (formerly known as the Food Stamp Program) and the National School Lunch Program. For each, I summarize how the program is structured, how eligibility is established, and how participation proceeds. Europe has generally used income-based assistance programs to improve the well-being of low-income households; I consider a couple of reasons for why food assistance programs may also be worth considering.  refugees, and those who had been exposed to violence or substance abuse. Overall, this review supports a link between food insecurity and mental health (and other factors, such as housing circumstances and exposure to violence) among women in high-income countries and underscores the need for comprehensive policies and programs that recognize complex links among public health challenges.  The objective of this review was to examine the methods used to measure food insecurity (FI) globally, to inform considerations relating to adopting a novel, or reviewing an existing, FI measurement approach in developed countries.

Households and individuals
Focus groups, surveys, secondary data analysis, and interviews Results found that the majority of papers reviewed emanate from North America with the US Household Food Security Scale Module (HFSSM) and its various adapted forms being the most commonly reported indicator. FI is becoming a key concern within developed countries with a range of indicators being used to report on the severity of the issue.  • Existing data on food insecurity are too diverse to admit a simple synthesis, but further research will generate findings that will permit a thoroughgoing analysis of the phenomenon.  The aim of the present study was to conduct a systematic literature review to identify all multi-item tools that measure food insecurity and explore which of the dimensions they assess.

Households and individuals
NA Eight multi-item tools were identified. All of the tools assessed the 'food access' dimension and two partially assessed the dimensions 'food utilization' and 'stability over time', respectively. 'Food availability' was not assessed by existing tools. Conclusions: Current tools available for measuring food insecurity are subjective, limited in scope, with a majority assessing only one dimension of food insecurity (access). To more accurately assess the true burden of food insecurity, tools should be adapted or developed to assess all four dimensions of food insecurity Note. Galluop surveys: Gallup uses telephone surveys in countries where telephone coverage represents at least 80% of the population or is the customary survey methodology. In the developing world, including much of Latin America, the former Soviet Union countries, nearly all of Asia, the Middle East, and Africa, Gallup uses an area frame design for face-to-face interviewing in randomly selected households.

Grey Literature
The grey literature part of the sample is composed by the thesis (n = 73), research and institutional reports (n = 36), conferences (n = 3), book chapters (n = 1) and newsletter pieces (n = 1). For periodical reports (like the FAO's SOFI), we have only considered the last version. Twenty records were published between 2000 and 2010, but the vast majority (n = 76) are posterior to 2015.
With regard to the countries where the data was collected, three of them report data from several countries-some including only developed but most also developing countries [2,68,69] five of them come from Australia [70][71][72][73][74], one from New Zealand [75], five from the UK [76][77][78][79][80], two from Spain [81,82], and 24 from Canada . The remaining 73 documents report data from the US .
Most documents provide data on the prevalence and correlations of food insecurity in the different territories and population groups, although a small sample (n = 4) also delves into the effect of interventions [99,141] or policy options [65,94].
Food insecurity was measured at the household level in 49 of the records, being the most used instruments the 18-item HFFSSM (n = 39), the 10-item HFSSM (n = 4), the 6-item HFSSM (n = 3), the single-item food insecurity question from the Australian NSW Population Health Survey (n = 1), the FIES scale (n = 2), the European Quality of Life Survey item "could your household afford a meal with meat, chicken or fish every second day if you wanted it?" (n = 1); Current Population Survey Food Security Supplement (CPS FSS), USDA (n = 1). Note that some of the studies use more than one measurement instrument.
The remaining 67 documents assessed food insecurity at the individual level, with a variety of profiles: three focused on adolescents, and used the 9-item CFSSM (n = 2) and the single-item Food Insecurity Measure (n = 1). Most records measured food insecurity in adults (n = 31), four of them being exclusively on women and used the 6-item and 18-item HFSSM, the 2005 Oregon PRAMS single-item Food Insecurity Measure and the HFIAS Scale. The other studies on adults comprise both gender and measure food insecurity through the 6-item (n = 10), 10 item (n = 6), 18-item HFSSM (n = 5), the Radimer-Cornell Food Insecurity Measure (n = 1), the 8-item food security questionnaire by Reid (1997) (n = 1), the single item Food Insecurity measure (n = 1), the Food Security Module at the LISA Study (n = 1) and the HFIAS scale (n = 1). Five additional studies were conducted on adults and children, and used the FIES scale (n = 2), 6-item HFSSM (n = 1) and 18-item HFSSM (n = 2); 23 on College students, and measured food insecurity through the 6-item HFSSM (n = 14), 10 item HFSSM (n = 2) and 18-item HFSSM (n = 7); and four documents reported measures of food insecurity on elderly, using the 6-item HFSSM (n = 2) and 10-item HFSSM (n = 1) and FIES scale (n = 1) (see Table 2).

Measures of Food Insecurity
Overall, our literature review identified 23 measurement tools to assess food insecurity at the individual or household level in high-income countries ( Table 3). The most used instruments are those of the USDA HFSSM which together (6, 10, 18 item versions) have been used in 71.8% percent of our sample. These are followed by the FIES (8%), HFIAS (2.7%) and the Single-item Food Insecurity question from the Australian NSW Population Health Survey (2%). The remaining 17 instruments were each used by one or two documents in our sample. The majority of instruments identified in this study were developed by institutions with the purpose of monitoring food insecurity, its severity and its correlations in several contexts. The first tools (Radimer-Cornell FIM; 18-item, 10-item and 6-item HFSSM), date from the nineties, whereas more than half of the instruments have been developed since 2005.
In total, 74% of instruments in our sample were validated. Not validated measures or measures for which validation information has not been found include the Australian single-item, the 2005 Oregon PRAMS single-item, the ENEP single-item, the question in the European Quality of Life Survey, the Food Insecurity Index, and the Healthy Diets ASAP. We found that 65.2% of the existent instruments in our sample measure food insecurity at the household level, while 17.4% measure food insecurity at the individual level (10-item HFSSM/AFSSM, CFSSM, Townsend Food Behaviour Checklist, and ENEP single-item) and 17.4% at both the household and individual level (Girard four point tool, LISA Food Security Module, Australian single-item, 6-item HFSSM). The target population of the most commonly employed food insecurity instruments such as the US-HFSSM (18-item and 6-item) as well as the HFIAS and FIES include all age groups within the household, i.e., children, adults and the elderly. The CFSSM of the USDA is the only validated child food insecurity instrument for children and adolescents aged 12 years or above. There are some differences between the US-FSSM and CFSSM. The CFSSM has been developed from the HFSSM; however, the former is simple without any screeners, easier to understand and can be self-administered in older children and teenagers. The keywords in each of the nine items of the CFSSM (i.e., worry, run out, cheap food, etc.) are underlined in order to ensure that the child comprehends the question.
Regarding the dimensions of food insecurity captured by the different instruments in our sample, it was evident that all the instruments in our sample focus on accessibility and availability of food mostly related to financial constraints. The USDA's instruments specifically focus on the psychological aspects of food insecurity concerning worry or stress and anxiety over not being able to procure or consume sufficient food. On the other hand, the eight-item New Zealand Food Insecurity measurement tool along with focussing on the psychological aspects of food insecurity also question participants about food assistance from family or other sources and reliance on food banks. It is evident from the instruments in our sample that the majority of them (83%) mainly focus on the quantity of food. Only 17% of the instruments in our sample, which include the Radimer Cornell Food Insecurity Measure, Brazilian Food Insecurity Scale, HFNSS and Healthy Diets ASAP, capture both the quantitative and qualitative aspects of food insecurity. Further, the Brazilian Food Insecurity Scale focusses on additional and interesting aspects of food insecurity including family expenses and food consumption while the Healthy Diets ASAP also covers the pricing of healthy food and drinks.
All the instruments in our sample have been developed in English including the Brazilian Food Insecurity Scale which was developed in Portuguese but includes an English version. 73.8% of instruments in our sample belong to the USDA which has developed different versions of its original HFSSM, including shorter versions and the self-reported module for older children or adolescents. The instruments in our sample have been most commonly used in the US (61%).
As noted in Table 4, some of the instruments have a large number of items in order to capture the perceptions of food insecurity in participants more effectively. The HFNSS has 26 items in its instrument while the US-HFSSM and LISA Food Security Module have 18 items. On the other hand, there are some instruments only use a single item in order to measure food insecurity such as the NSW Population Health Survey, single item Australia, Oregon PRAMS, ENEP and EQLS. These instruments are simple and easy to employ yet may not be able to capture all aspects of food insecurity.
Most of the food insecurity instruments in our sample including all of the USDA's instruments have a time frame of either 30 days or 12 months. The psychometric properties of all validated instruments (74%) in our sample have been found to be good. As noted in Table 4, we have identified several reported strengths of the different food insecurity instruments especially the US-HFSSM, which is considered to be a comprehensive survey that captures different levels of severity of food insecurity within the household. At the same time, various issues and unmet challenges have been described regarding these tools, which need to be addressed. The underlying issue that arises with most of these instruments including the US-HFSSM is that it does not capture the qualitative aspects of food insecurity. However, some of the challenges that have been found in these instruments are related to respondent burden due to the lengthy nature of the survey as in the case of the 18-item US-HFSSM, whereas shorter versions, like the Australian single-item FI indicator, may not adequately capture the intensity and complexity of food insecurity. Notwithstanding that, the main issue as in the case of the commonly used food insecurity indicators such as the US-HFSSM is related to the lack of items questioning the respondent about dietary quality.

Discussion
Research on food insecurity in high-income countries is only increasing-as observed by the growing number of papers and other documents published in recent years. This trend actually reflects a highly noticeable social and health-related issue, which is the alarming volume of households and individuals in the rich world that cannot see their fundamental right to adequate food guaranteed, as recognized by the Universal Declaration of Human Rights [180]. In a more recent version, the Sustainable Development Goals (especially SDG 2 and 3) emphasize the relevance of tackling this situation-and in fact, the FIES Scale was developed as a tool to assess the progression of SDG2 [181]. It is also urgent to adequately assess and monitor the scope of food insecurity, as it is by better comprehending the extent, correlations, causes and consequences of such phenomena in the different contexts that it will be possible to provide the most adequate solutions. One of the biggest challenges to this endeavor is the complexity of the phenomenon of food insecurity itself, which, when considering all its dimensions (availability, access, use and stability), encompasses not only the entirety of the food system, but also the personal and household experiences of those suffering from it. In this way, it adds a layer of intricacy, as it mixes objective and subjective perspectives.
In our review, we have identified 23 instruments to assess food insecurity at the individual or household level in high-income countries. The most used instruments are those of the USDA HFSSM followed by the FIES, HFIAS and the Single-item Food Insecurity question from the Australian NSW Population Health Survey [2,67,68,175]. These scales assess the experience of food insecurity at the access dimension, either at the household or individual level. Assessing the experience of food insecurity means that it is the subjective perception of the respondents about food what is being considered (i.e., in the questions such as the HFIAS In the past four weeks, were you or any household member not able to eat the kinds of foods you preferred because of a lack of resources? or In the past four weeks, did you or any household member have to eat a limited variety of foods due to a lack of resources?). It is interesting to note that although some of the studies identified in this review focused on specific populations like women, college students or the elderly, the scales used are not unique for this target-something that in the case of the elderly might be considered, given their particular conditions [25].
The fact that the USDA HFSSM scales have been the most used in our sample (in more than 70% of the documents), is coherent with the point that we are studying food insecurity in high-income countries [2]. The FIES and HFIAS were initially conceived to be used in low-income countries, but they have also been used in high-income ones, either for comparative purposes [2,69] or for selected deprived areas or populations [59,182]. In any case, the three sets of scales share a high number of common items, since the HFIAS was developed based on the HFSSM scales and has, in turn, informed the development of the FIES scale together with the Latin American and Caribbean Food Security Scale (ELCSA) [25,183]. They differ from each other by including or not including aspects related to the possibility of satisfying one's (household) food preferences (HFIAS) or accessibility to nutritious food (HFSSM/FIES). In this sense, they collect information that refers to the contextualization aspects of the concept of food insecurity [17] since these seem to be elements more relevant to the subjective experience of food security in high-income societies-where availability of a wide variety of foods is guaranteed.
Since dietary intake is one of the main determinants of health [184], food insecurity must be considered a relevant axis of health inequalities, and dietary quality should be considered in any action developed to reduce it. Therefore, we agree with Shanks [185] that the measurement of dietary diversity (and we may add food quality) to characterize food insecurity is essential. This is in fact one of the missing points of current scales to measure food insecurity-in our review, only three of the instruments found assessed both quantity and quality aspects of food intake, and were the least used. Moreover, although there exist specific instruments to measure it (such as the Household Dietary Diversity Score), these instruments are yet not very much implemented. In that sense, special interest was observed among the instruments used in the literature to add items considering health and socioeconomic aspects related with food insecurity such as family income, expenses and food consumption, but also structural issues like social programs and policies, which should systematically be included in food insecurity studies.
Assessing dietary diversity entails a challenge that echoes some of the traditional disputes on the measurement of food insecurity [28], namely the use of objective or subjective/experiential scales. In this way, while being able to capture people's (and their household's) experiences of food insecurity is essential, characterizing adequate food intake requires using objective measures. It means that while questions like the FIES "You were unable to eat healthy and nutritious food?" or the HFSSM "(I/we) couldn't afford to eat balanced meals" provide information about the respondent's perceptions of their food access possibilities, it might not fully reflect what from a public health perspective would be considered a proper diet. Additionally, given how current food systems have evolved with the proliferation and accessibility of ultraprocessed foods, looking only at the number of food groups consumed may not suffice to gain a proper view of diet quality, and therefore it might be necessary to complement current food insecurity scales with other traditional food intake recalls such as food diaries, 24 or 72 h recalls or food frequency questionnaires. In addition, another important aspect to take into account is that access to drinking water (water security) is not valued.
The scales identified in this review focus on the access dimension of food insecurity, and efforts should be made to also capture the use dimension, as well as other relevant aspects such as the environment of adequate sanitation, health services and care, allowing for a healthy and active life which the FAO 2012's definition of food insecurity recognizes [14]. This is something that Pereira and colleagues [186] described in the case of children, and is applicable to the case of adults as well.
Of course, reaching such a rich amount of data on the different dimensions of food security and its determinants (and consequences) may be at odds with the practicalities of data collection. It is in this case that the range of options available-in terms of number of items and length of the scales-must be considered to obtain the more complete data, as compatible with the requirements and possibility of each study.
This review is not exempt from limitations. Mainly, the algorithm used to identify the literature uses the term "high-income countries", but no individual country name. In this way, some single-country studies may have not been identified. However, the inclusion of gray literature and the considerably sizeable sample make it a complete reference to provide a comprehensive view of the instruments used to measure individual and household food insecurity in high-income countries.

Conclusions
This work supplements and expands on previous reviews on measures of food insecurity in high-income countries by maximizing the searched databases, applying no limits to the nature of the measure (single-item, survey-based, etc.) and including scales used in studies published in the gray literature. In this way, it offers an updated and comprehensive catalogue of instruments to measure food insecurity at the individual and household level in high-income to be used by both researchers and practitioners.
As it has been previously recognized, no 'perfect single measure that captures all aspects of food insecurity' exists, but efforts should continue to improve our understanding of food insecurity, combining both objective and subjective elements of assessment. Therefore, this scoping review considered that further research is required in terms of (i) the creation and/or improvement of validated measurement for food insecurity in high-income countries, (ii) the incorporation of food quality and dietary intake items to assess the food use, and (iii) the consideration of aspects such as the household composition, the economic situation of the individuals and households, their use of social resources and food aid and their food literacy and competences.