Investigating and Quantifying Food Insecurity in Nigeria: A Systematic Review

Abstract

Given the recent increase in the number of Nigerians estimated to be at risk of food insecurity, it is crucial to explore the array of tools used to quantify food insecurity (FI). This exploration will help determine the prevalence and severity of FI in Nigeria. This review explored the scope of FI research carried out in Nigeria to examine how the design was quantified. A systematic review was performed to compile the accessible Nigerian studies. Seventy-nine studies were reviewed. Eighteen used the Household Food Insecurity Access Scale module (HFIAS) to investigate FI status; thirteen used the recommended daily calorie requirement approach; twelve employed the Household Food Security Survey Module (HFSSM); ten used the food insecurity index (through household per capita food expenditure); seven used the Food Insecurity Experienced Scale (FIES); two used the Food Consumption Score (FCS); and the others employed less standardized or thorough approaches. Different prevalence levels and gravities of FI in the Nigerian populations were documented. The prevalence of FI varied from 12% to 100%, based on the instrument and demography being studied. In accordance with the findings of this review, the authors propose standardization of the FI instrument and highlight the need for a measurement tool that would be appropriate for the Nigerian setting. This will enable researchers to attain a comprehensive knowledge of the occurrence rate of FI in Nigeria, leading to improved food- and nutrition-sensitive policy development.

1. Introduction

The global community is faced with one of the most challenging issues in recent times—food insecurity. Food insecurity (FI) is experienced in almost all regions of the world, especially in Asia and Africa, as more than 50% (425 million) of the people in the world affected by hunger in 2021 were in Asia and more than one third (278 million) lived in Africa [1]. About 12% of the world’s population was affected by severe FI, while more than 2 billion people were either moderately or severely food insecure in 2021 [1].

According to the 2023 Global Report on Food Crises, more than one quarter of a billion people are experiencing acute levels of hunger, while some are on the verge of extreme deprivation of food [2]. Increases in conflict events, rising poverty, escalating inequalities, widespread underdevelopment, climate crises, and the COVID-19 pandemic have also contributed to the worsening of global food insecurity [2]. It is worth noting that Africa (especially sub-Saharan Africa) is experiencing worsening FI, which is reflected in the inclusion of six African countries (Sierra Leone 40.5/100, Madagascar 40.6/100, Burundi 40.6/100, Nigeria 42/100, Sudan 42.8/100, and the Congo Dem. Rep. 43/100) among the top 10 bottom-ranking countries with the lowest Global Food Security Index (GFSI) score in the 2022 overall food security environment. No African countries were among the top 10 high-ranking countries [3]. According to the Food and Agriculture Organization (FAO) and its partners’ projections, the impact of the Russia–Ukraine war threatens food security globally. The ripple effect of the war will have numerous implications for global agricultural markets, and this can potentially worsen the state of food and nutrition security for many nations in the coming years [1].

Food insecurity and hunger are on the rise in Nigeria. In January 2023, the United Children Fund (UNICEF) projected that 25 million Nigerians are at risk of experiencing hunger by the third quarter of 2023. This revealed an increase of about 8 million in hunger from the 2022 estimates [4]. Nigeria ranked 107th out of 113 countries and 25th out of 28 sub-Saharan Africa (SSA) countries with a GFSI score of 42/100 in the GFSI 2022 [3,5]. Also, in the 2022 Global Hunger index (GHI), Nigeria ranked 103rd out of 121 countries, scoring 27.3/100. This indicates a serious level of hunger and suggests that Nigeria is not on track to achieve the Sustainable Development Goal 2 (SDG2) target by 2030 [5,6].

X-raying the food security environment in Nigeria, as reported in the GFSI 2022 under the four pillars for food security (Figure 1), indicated that Nigeria had the lowest score (25/100) globally on the affordability category. In the availability category, Nigeria ranked 108th globally and 26th in the region. The report showed that the very weak performance score (39.5) was a result of the “very weak” (0–39.9) scores obtained in certain indicators, such as agricultural research and development (30.7/100), supply-chain infrastructure (23.9/100), sufficiency of supply (25.5/100), political and social barriers to access (31.6/100), and food security and access policy commitments (0/100) [3].

Figure 1. Authors’ graph using data from the Global Food Security Index, 2022.

Food security (according to the United Nations definition) is referred to as “People having at all times, physical, social and economic access to sufficient, safe and nutritious food which meets their dietary needs and food preferences for an active and healthy life” [7]. The term “food insecurity” simply refers to the opposite of food security, where conditions of food security are not met, and it can be broadly conceptualized along a range from mild to severe [8]. The definition contains four widely established pillars of food security, namely: availability, accessibility, utilization, and stability. The four pillars are important in understanding food security at any level, such as regional, household, and individual levels [9,10,11,12,13,14,15].

Generally, conditions that expose people to FI and hunger include extreme poverty, unemployment, corruption, unstable food access, ill health, non-existent social protection programmes, and terrorism [8,14,15,16,17,18,19]. FI is not only experienced in developing nations, as developed nations are also affected. In Australia, for instance, over 2 million households were affected by severe FI in 2022 [20], while in the United States of America (USA), an estimated 14.8% of children resided in food-insecure households [8,21]. It is generally believed that FI risk is unevenly distributed. The most vulnerable groups, such as children, women, the elderly, and internally displaced people (IDPs), usually suffer higher levels of FI [8,19,22,23,24,25]. FI may be momentary in nature, given the possibility of households slipping into and coming out of FI in response to evolving situations, supporting the idea that FI is best conceptualized as a dynamic phenomenon rather than a fixed construct [15,26,27,28,29]. In consideration of the weighty possible implications of FI, comprehending the methods employed by researchers to study FI, and the results obtained, are instrumental in designing food- and nutrition-sensitive policies and their implementation. About two and a half decades ago, many researchers carried out FI research in Nigeria, utilizing various measuring tools like their counterparts in other parts of the world. Several approaches have been established to study FI across global, national, and household/individual domains [11]. About three decades ago, FI measurement tools were used to assess economic access to food, using, for instance, household income or the Household Consumption and Expenditure Survey (HCES) as proxies for food security, although the measures did not capture the experiences of households accessing food or the strategies employed in coping with insufficient food access. To overcome this limitation, the Radimer/Cornell scale (experience-based) was created [30]. In most cases, other experience-based approaches that were developed from [30] hinged on three central themes: “anxiety/uncertainty over running out of food, concerns over and adjustments to the quality, and quantity of food in the diet” [8,30]. The tools used different recall periods (30-day, 12 months) where the gravity of FI is in relation to the quantity of agreeable answers, with a higher number revealing extreme conditions [8,30]. The United States Department of Agriculture (USDA) Household Food Security Survey Module (HFSSM) is another approach commonly used in US-based studies for measuring FI, and it has been extensively adopted in many other countries. The module contains a lineup of questions (18 items) developed from the collective insights of FI at the household level, and it is executed through a survey-based measurement, usually within the timeframe of the prior 12 months. The findings may be presented as an unbroken continuum of severity, or by applying cutoff levels to assign households to four specific categories. In the absence of children, the module utilizes 10-item questions. It is crucial to highlight that HFFSSM adopts a flexible scoring system instead of a strict numerical threshold for classifying households [8,15,31,32].

The Household Food Insecurity Access Scale (HFIAS), created by the Food and Nutrition Technical Assistance Project (FANTA), is also another FI measuring tool that has been tested and approved in various countries and widely used across the globe [33]. The module utilizes nine-item questions, which centre on the household food access experience within a 30-day recall. The households are categorized into four categories depending on the severity experienced, from food secure to varying levels of FI [33]. The Food Insecurity Experience Scale (FIES), developed by the FAO, is the most recent tool used in measuring FI. The FIES utilizes eight-item questions, which relate to occurrences during the preceding 12 months. This approach prioritizes the subjective experiences shared by the interviewed individuals and downplays the role of money in food access [8,34,35]. In contrast to the HFIAS and HFSSM, the FIES measures individual FI and has been extensively utilized in the assessment of FI [8,15,34,35,36,37,38,39,40,41]. The food insecurity index is another construct for estimating household FI through the mean of per capita household food expenditure (MPCHFE). In this method, the line of household food security is established at two thirds of the MPCHFE; while households are food secure if their MPCHFE surpasses the food security line, they are classified as food insecure if they fall below it. The approach is commonly utilized in African studies; for instance, in Nigeria and Ethiopia [42,43,44,45,46]. Another approach to estimating household FI involves investigating the food security status of each household by comparing their food consumption against the established food security threshold using the recommended daily calorie requirement. The households satisfying or surpassing the recommended daily calorie intake (1800–2710 Kcal in most studies) are categorized as food-secure households while those households that fall below the threshold are grouped as food insecure [47,48,49,50]. The use of the Food Consumption Score (FCS) is another key performance measure created by the World Food Programme (WFP) for assessing the occurrence of FI in a country or region (WFP 2007; Jones et al. 2013). It is significantly guided by the knowledge of how dietary diversity and household food access are interconnected. This approach uses 7-day recall, while the study participants report on the consistency of the household consumption of eight food groups. The food consumption recurrence of each food group is then multiplied by an assigned weight for each group, while the values derived are added together to obtain the FCS. This score is then transcribed to a discrete variable using standard cutoff values [11,51]. This approach is not widely utilized by researchers in various countries or regions, unlike HFFIAS, HFSSM, and FIES. Taking into account the extensive body of academic literature and research that has explored FI over some decades, it is noteworthy that there are systematic reviews (SRs) on food (in)security in different countries and regions, but those that focus on assessing and quantifying FI in Nigeria are quite scarce. For instance, there exist SRs of the literature on the understanding and measurement of FI in Australia [15], the associated factors of FI in older adults in the USA [52], the FI studies in South Africa, which point out opportunities for enriching policy insights [53], and the effects of agricultural interventions on food security in northern Ghana [54]. At the regional level, [55] explored a descriptive SR on FI and health outcomes in Southern Africa, while [56] reviewed the interconnectedness of household FI, dietary diversity, and stunting in SSA. This study is the first SR that is devoted to investigating food security research in Nigeria. The approaches utilized by researchers are similar to those in other parts of the world, employing various methods, such as HFIAS, HFSSM, and FIES (the most recent), to estimate FI [19,41,57]. While some studies utilized researchers’ constructs, others modified or adapted approaches from standardized measures, especially the HFSSM, leading to one-item and three-item questions [58,59,60,61]. However, inconsistencies in measuring FI are likely to impact the reported occurrence, which affects food- and nutrition-sensitive policy development. The purpose of this review is to systematically assess the scientific research papers that claim to examine FI in Nigeria; explore the diversity of scholarly investigations, with their measurement tools in Nigeria; and present a broad picture of the gravity of FI in Nigeria as highlighted in these scholarly articles.

2. Methods

A systematic exploration was embarked upon to find all of the research works carried out in Nigeria on food (in)security. The key search terms were “food insecurity” OR “food security” OR “food availability” OR “food utilisation” OR “food access” AND “Nigeria.” The searched databases included PubMed, the Lens database (https://www.lens.org/ (accessed on 25 July 2023)), and SCOPUS. In order to gain a full collection of scholarly papers that reported on FI in Nigeria, no restrictions were placed on the date of publication. However, only scholarly papers published in English were considered, while research documents, such as unpublished articles, books, book chapters, conference abstracts, encyclopedias, theses, dissertations, editorials, and reviews, were debarred. All identified scholarly papers were downloaded into EndNote X7.

The literature search identified 1783 studies, out of which 853 were duplicates. The titles and abstracts of the remaining 930 studies (original research papers) were read consciously, while 708 studies were found not referring directly or indirectly to FI research in Nigeria, resulting in 222 studies left for another stage of assessment. However, only studies with full-text access were reviewed. Publications that failed to meet the inclusion criteria were removed at this stage, while others that may meet the criteria for another level of investigation were kept for further examination. The full texts of 222 studies were obtained for another level of assessment. The authors individually read all of the articles at this stage and determined if each publication would be retained based on the inclusion criteria. Out of the 222 studies, 124 were removed for not meeting the inclusion criteria upon closer assessment. Meanwhile, 19 additional articles (to give a total of 143 studies) were removed as a result of no identifiable method of measuring FI and no record of FI prevalence rate in the studies (for instance, [62,63,64,65]). Furthermore, the reference lists of articles were equally checked in case there might be studies that met the inclusion criteria. However, this search did not yield any additional articles. Only 79 studies have been included in this review, as presented in Figure 2. In this stage, information drawn from these studies includes the location of the study; the population group; the study focus; the findings; the primary method; the measured FI; the method for assessing FI; FI prevalence; and the number of respondents.

Figure 2. Flowchart of studies that met the search criteria, and the total number of studies included for review.

3. Results

The brief snapshot of the key insights obtained from the 79 included studies is presented in Table 1 below.

Table 1. Snapshot of the key insights obtained from the 79 scholarly articles included in this review.

Reference	Location	Population Group	Study Aim	Findings	Primary Method	Method for Assessing FI	FI Prevalence	Respondents
[57]	Oyo and Lagos states	School-going children in Lagos and Ibadan	To delineate the food security status of households headed by teachers in public and private schools	The prevalence of food security (26%) in teachers’ households in Lagos and Ibadan was low, while the food security level of households in Lagos was better than those in Ibadan	Survey (Cross-sectional)	USDA 18 Question Households Food Security Module (HFSSM)	76.3% (Ibadan); 72% (Lagos)	482 households
[62]	Borno state	Rural households	The study examined and analyzed the food security status of rural households in Borno state	The results indicated that a FI line of NGN 23,700.12 or USD 176.87 per adult equivalent per year was obtained among households in the state	Survey (Cross-sectional)	Recommended daily energy level approach (2250 Kcal)	58.0%	1200 households
[47]	Kwara state	12 villages of rural farm households	To investigate the socioeconomic attributes and correlates of FI of rural farming households	About 36% of the farm households were food secure while 64% were food insecure. Thirty-eight percent of the food-insecure households did not meet the recommended calorie intake	Survey (Cross-sectional)	Recommended daily calorie required approach (2260 Kcal)	38.0%	94 rural farm households
[66]	Lagos state	Professionals, artisans, traders, and unemployed	To analyze the food security situation among urban households in Kosofe LGA of Lagos state	The study indicated that FI was higher in FHHs than in MHHs. The study also reported that FI reduces when the education level goes up	Survey (Cross-sectional)	Food security Index: Per capita food expenditure (food security line = N7, 967.19)	Professional (55%); Artisan (19%); traders (22%); unemployed (4%).	165 urban households
[67]	Ekiti state	16 villages of farming households in two Agricultural Development Project zones	To investigate food security situations among rural farm households in Ekiti state	The study reported 12.2% food secure and 87.8% food insecure farm households in the study area. Also, cassava, yam, and their products were found to contribute greatly to the food security status of the farming households	Survey (Cross-sectional)	USDA 16-Question HFSSM approach	87.8%	160 farm households
[68]	Nassarawa state	15 farming communities in 3 LGAs	To determine food security status and the optimal farm plan of farming households in 3 LGAs of Nassarawa state	The study revealed 58.9% FI among farming households. Also, maize, yam, and cassava were identified as significant food security crops among farm households	Survey (Cross-sectional)	Recommended daily per capita calorie intake of 2470 Kcal	58.9%	180 farm households
[69]	Abuja	Urban households in three wards (Quarters, Central, and Kuttunku)	To assess the food security status of urban households in FCT	The study reported that 70% of urban households were food secure, while 30% were food insecure	Survey (Cross-sectional)	Food security scale and frequency counts (developed by Freedom from Hunger (FFH))	30.0%	120 urban households.
[70]	Osun state	Ife Central LGA (rural and urban settlements)	To assess the influence of family size, household food security status, and childcare practices on the nutritional status of under-5 children in Ile-Ife, Nigeria	Under-5 children in food-insecure households were 5 times more likely to be wasted than in food-secure households	Survey (Cross-sectional)	18-item HFSSM approach	65.0%	423 (Under-five children/mothers)
[71]	Kwara state	40 villages in 8 LGAs of Kwara state	To examine the effect of off-farm income on household calorie and micronutrient supply, dietary quality, and child anthropometry	The study reported that off-farm income had a positive net effect on food security and nutrition.	Survey (Cross-sectional)	Recommended daily calorie required approach (2500 Kcal)	N/A	220 households
[72]	Oyo state	One LGA (Ogbomoso South) of Oyo state. Participants and non-participants in development programmes	To assess rural women’s participation in development programmes and their food security status	The study reported that 93% of the respondents were aware of the development programmes while 23.6%, 60.9%, and 15.5% indicated high, average, and low levels of participation, respectively	Survey, focus group discussion (FGD)	Household Food Insecurity Access Scale (HFIAS) Approach	52.7%	110 respondents
[73]	Delta state	8 communities in Warri, Delta state	To investigate food insecurity incidence in an “oil city’’ of Warri, Nigeria	The study revealed that food insecurity incidence decreases as the level of income increases. Also, household size had a direct relationship with food insecurity incidence	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach (food security line = N10, 704.27)	Oil workers (42%); traders (23%); civil servants (23%); unemployed (6%).	260 households
[74]	Edo state	Egor LGA	To assess food insecurity situations in Egor LGA of Edo state	Food insecurity was higher among female-headed households (FHHs) and those with larger household sizes	Survey (Cross-sectional)	HFIAS approach	61.8%	416 households
[75]	Ado-Ekiti, Ekiti state	5 political wards in 10 streets of Ekiti	To investigate food insecurity and coping strategies in Ado-Ekiti, Ekiti state, Nigeria	The overall food insecurity status of the households was 58.8%, while the depth of food insecurity (expressed as the average percent increase in calories required to meet the recommended daily requirement) was 19.5%	Survey (Cross-sectional)	Recommended daily calorie required approach (2550 Kcal)	58.8%	80 households, 321 members
[76]	Ogun state	3 senatorial districts in Ogun state	To assess coping strategies for food security among the elderly in Ogun state, Nigeria	The study reported that 88% of the participants were food secured. The coping strategies reported were the use of cooperatives, banks, and daily money savings	Survey (Cross-sectional)	Assessing food habit	12%	310 participants
[77]	Lagos state	3 LGAs based on income groups: Ikoyi (high income), Surulere (middle income), and Agege (low income)	To assess the prevalence of food insecurity and the level of household food access in the Lagos metropolis	The study revealed that households in the Lagos metropolis had adequate food access with an HFIAS score of 6.45 ± 0.41 (harvest period) and that it worsened significantly to mean food access of 12.44 ± 0.45 during the hunger period	Survey (Cross-sectional)	HFIAS approach	Low-income group (50.8%); Middle income (51.7%); High income (27.5%)	180 households
[78]	Oyo state	2 LGAs in Ibadan; Ibadan North West and Ibadan South West	To examine gender role attitudes as they affect food insecurity in the Ibadan Metropolis	The study reported that the pattern of gender role attitude is quasi-traditional, while an egalitarian disposition to gender roles is yet to be firmly rooted, and food insecurity is still a plague among women	Survey (Cross-sectional)	The 4-item women’s hunger sub-scale	87.8%	617 households
[79]	Ondo and Ogun states	8 LGAs comprising 24 communities in the two states	To examine off-farm activity participation, technology adoption, and impact on the food security status of Nigerian farming households	The study reported that the impact of improved technology adoption on the food insecurity level of adopters with off-farm activity was higher than their counterparts without participation	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach (food security line = NGN 20,132.22)	50.7% (technology adopters); and 56.3% (technology non-adopters).	482 households
[49]	Osun state	Three agricultural zones, namely: Osogbo, Iwo, and Ife/Ijesha	To investigate the food security status of households in Osun state of Nigeria	The study revealed that most of the households fell below the recommended daily per capita calorie intake, with a food insecurity gap of 0.0038	Survey (Cross-sectional)	Recommended daily calorie required approach (2710 Kcal)	54%	150 households
[80]	Enugu state	3 rural communities in the Nsukka LGA	To investigate household nutrition and food security in a rural community of the Nsukka Local Government Area (LGA) of Enugu state, Nigeria	About 43% were subsistence farmers, and 27% depended on borrowing food items to cope with nutritional and food security challenges	Survey (Cross-sectional)	USDA FSSM Approach	93.5%	263 households with 87 under-five children
[48]	Oyo state	Rural maize farm households in Oyo and Shaki	To examine the effects of maize biodiversity on the household food security status of rural maize farm households in the Southern Guinea Savannah of Oyo state, Nigeria	The study reported that food security headcount increases with maize richness, cultivar evenness, and relative abundance	Survey (Cross-sectional)	Recommended daily calorie required approach (2260 Kcal)	23.5%	200 households
[81]	Ondo state	Maize farming households in 44 villages	To assess ICT usage and household food security status of maize crop farmers in Ondo state, Nigeria.	The study revealed that cell phones, radio, and television were the most available ICT tools for accessing information on food security dimensions	Survey (Cross-sectional)	HFIAS Approach	52.4%	212 rural farmers
[82]	Anambra state	4 rural LGAs, namely: Anyamelum, Ogbaru, Anambra West, and Anambra East LGAs	To examine gender perspectives of the implications of the severe 2012 flood on household food security in rural Anambra state	The study reported a higher level of food insecurity in both male-headed and female-headed households after the 2012 flood incident in the study area	Survey (Cross-sectional); FGD	Food Security Index Approach (3-item question)	Before the flood: FHH, 11%; male-headed households (MHHs), 16%. After flood: FHH, 78%; MHH, 66%.	240 households (120 [MHHs] and 120 [FHHs])
[83]	Edo state	3 LGAs in 15 rural communities	To examine rural households’ food security status and coping strategies in Edo state	The study revealed that less than half (47.3%) of the rural households were classified as food secure	Survey (Cross-sectional); FGD	Recommended daily calorie required approach (2100 Kcal)	52.7%	150 rural households
[59]	Abia state	Three autonomous communities, namely: Akanu Ukwu, Okamu, and Isiama in Ohafia	To examine gender roles, family relationships, food security, and the nutritional status of households in Ohafia	The study reported that 65.5% of the households were said to experience little or no hunger, whereas 33.8% experienced moderate hunger, and 0.7% had severe hunger	Survey (Cross-sectional); FGD	Household Hunger Scale (HHS); dietary diversity score	66.0%	287 households
[84]	Ogun state	People living with HIV in Sagamu	To determine the prevalence of household food insecurity and its associated factors among people living with HIV in Sagamu, Ogun state	The study reported that food insecurity was associated with major predictors, such as educational status, occupation, type of housing, delaying drugs to prevent hunger, and exchanging sex for food	Survey (Cross-sectional)	HFIAS Approach	71.7%	244 adult participants
[85]	Nigeria	Polygynous family structures	To explore the relationship between polygyny (man marrying more than one wife) and food security in Nigeria	The study revealed that at the household level, polygynous households are found to have better food security outcomes than monogamous households	Survey (secondary General Household Survey panel data)	Food consumption score; reduced coping strategies index (RCSI)	N/A	5000 households
[86]	Oyo state	Households in the Ibadan Metropolis	To determine the correlates of food insecurity of households in Ibadan Metropolis	The study reported that the estimated food insecurity line was NGN 1948.82	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach (food security line = NGN 1948.82)	29.3%	150 households
[87]	Oyo and Ogun state	5 LGAs in Oyo and 4 LGAs in Ogun	To determine food insecurity risk perception and management strategies among households in Ogun and Oyo states	The findings indicated that the majority of the households (87.6%) manifested various forms of food insecurity risks	Survey (Cross-sectional)	Assessing food insecurity risks	87.6%	161 households
[88]	Kaduna state	Urban farmers in Kaduna North, Kaduna South, Jema’a, Zaria, and Sabon Gari LGAs	To investigate food security and productivity among urban farmers in Kaduna state	The results revealed that 54.5% of the households were food insecure, while the average daily per capita calorie intake for food-secure households was 5516.28 kcal	Survey (Cross-sectional)	Recommended daily calorie required approach (2250 kcal)	54.5%	213 urban households
[89]	Gombe state	Farming households in 8 villages in Southern Gombe	To determine food access status among farming households in the southern part of Gombe state	The findings showed that about 27 percent of the farming households were food secure, 35 percent were mildly food insecure, 18.3 percent were moderately food insecure, and 20 percent were severely food insecure	Survey (Cross-sectional)	HFIAS Approach	73.5%	120 households
[90]	Four undisclosed states	MicroVeg projects beneficiaries	To examine factors influencing household food security amongst MicroVeg project beneficiaries in Nigeria	The findings revealed that household composition (more specifically, the ratio of male members in the active working age bracket) was found to influence food security among households	Survey (Cross-sectional)	HFIAS Approach	45.8%	120 households
[91]	Lagos state	Urban households in Shomolu LGAs	To assess the level of food security among urban households in Shomolu LGA, Lagos state	The results showed that food insecurity was found to be positively associated with indicators of poverty among urban households	Survey (Cross-sectional)	HFIAS Approach	66.2%	306 households
[92]	Kwara state	Farm households in 20 villages.	To assess the effect of sustainable land management (SLM) technologies on farming households’ food security in Kwara state	The study revealed that to reduce the effect of food insecurity, the effective coping strategies adopted by the households include a reduction in the quantity and quality of food consumed, off-farm jobs, and the use of money proposed for other purposes to buy foods	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach (food security line = NGN 4219.787)	65.0%	200 households
[93]	Ogun state	Rural community of Ode-Remo	To assess food security and dietary diversity among adults in a rural community in Remo, Ogun state	The study revealed that only 43.6 per cent of the respondents were food secure, while 43.4 per cent were severely food insecure, 30.3 per cent were moderately food insecure, and 26.3 per cent were mildly food insecure	Survey (Cross-sectional)	HFIAS Approach	56.4%	134 adults
[94]	Enugu and Imo states	Undergraduate students of 2 universities in Enugu and Imo states	To assess the prevalence of food insecurity and associated factors among university students among students in Enugu and Imo states	The study found that food insecurity was significantly associated with monthly allowance, daily amount spent on food, and source of income	Survey (Cross-sectional)	10-item USDA HFSSM Approach	80.7%	398 university students
[95]	Osun and Oyo states	Working poor households in 6 towns in both Ogun and Oyo states	To examine the factors influencing the food insecurity status of the working poor households in southwest Nigeria	The study showed that more than half of the respondents were working poor households, with more than four fifths of them being food insecure	Survey (Cross-sectional)	HFIAS Approach	Working poor: severely food insecure (85.7%). Working non-poor: severely food insecure (12.3%)	284 households
[96]	Anambra and Imo states	Households that have experienced flooding in Imo and Anambra states	To assess the pre- and post-flood households’ food security status in southeastern Nigeria	The results showed that flooding affects food security negatively by increasing the number of food-insecure households to 92.8%	Survey (Cross-sectional)	USDA HFSSM Approach	Before flood: 66.7%; After flood: 92.8%	400 households
[97]	Anambra, Enugu, and Ebonyi	Crop and livestock farming households	To assess the livelihood strategies adopted by husbands and wives within the same households for coping with climate-induced food insecurity in southeast Nigeria	The results indicated that 90% of the wives were more food insecure than their husbands (79.2%). The respondents noted that the observed changes in the climate contributed immensely to their food insecurity situation	Survey (Cross-sectional); FGD; key informant interviews (KIIs)	USDA HFSSM Approach	Wives: 90%; Husbands, 79.2%	120 pairs of spouses (husbands and wives)
[50]	Benue state	Rural farming households in 6 LGAs of Benue state	To assess the food security status of rural farming households in Benue state	The results revealed that 49.7% of the rural farming households acquired 2100 Kcal and above per capita per day and were, therefore, classified as food secure	Survey (Cross-sectional)	Recommended daily calorie required approach (2100 kcal)	56.9%	360 rural households
[98]	Nigeria	Male-headed and female-headed households	To investigate food (in)security and poverty dynamics amongst male-headed and female-headed households in Nigeria	The study found that female-headed families are more vulnerable to higher incidences of food insecurity than male-headed households, and with an overall significant urban food security advantage compared to rural areas	General Household Survey (GHS) cross-sectional panel data	12 months and 7 days recall of food shortages or inadequacy	MHHs: 2010—National (28.2%) 2012—National (25.0%) FHHs: 2010—National (34.6%) 2012—National (43.0%)	5198 households
[99]	Abuja; Abia and Enugu; Rivers; Ogun and Oyo	Cassava farming households	To investigate the effects of social capital on the food security of cassava farming households	The results revealed that membership density, cash, and labour contribution significantly affected food security in the study areas	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach	59.0%	775 households
[39]	Ogun state	Households in Odeda LGA of Abeokuta	To assess the household food insecurity status and coping strategies in Abeokuta, Ogun state	The results revealed that only 15.6% of the households were food secure, while the majority (84.4%) of respondents were food insecure	Survey (Cross-sectional)	Food Insecurity Experience Scale (FIES)	84.4%	250 households
[100]	Kaduna and Kebbi; Niger and Nassarawa; Taraba states	Maize farmers	To analyze the effect of adopting six Agricultural Practices with CSA Potentials (AP-CSAPs) on the food security status of maize farmers from northern Nigeria	The study showed that 37.0% of the farm households were food insecure, while adoption of the AP-CSAPs was generally low	Survey (Cross-sectional)	USDA HFSSM Approach	37.0%	238 households
[101]	Enugu state	Female-headed farming households	To examine the food security situation of female-headed households in Enugu state, Nigeria	This study revealed that poverty was found to be a major cause of food insecurity among female-headed households	Survey (Cross-sectional)	Perception of food security situation (using monthly food expenditure) in comparison to that of last year (2018)	Much worse, 25.7%; A little worse now, 47.0%; same, 14.3%;	72 FHHs
[102]	Borno state	School-aged adolescent girls	To determine the level of food security and hygiene among adolescent girls in the study area	The study revealed a high prevalence of low food security among adolescent girls	Survey (Cross-sectional)	9-question food security questionnaire	92.7%	562 school-aged adolescent girls
[103]	Kaduna state	Smallholder households	To examine the effect of smallholder socioeconomic characteristics on farming households’ food security in northern Nigeria	The findings indicated that the majority of households had low incomes and low educational attainment, which usually affects food security	Survey (Cross-sectional)	Income level, education attainment, and government policy	81.7%	120 households
[104]	Nigeria	Households in rural and urban Nigeria	To investigate the effects of non-seasonal food price volatility on household food security in Nigeria	The results revealed that imported rice price increases are damaging to both dietary diversity and the food share of consumption expenditure	General Household Survey (GHS) cross-sectional panel data	HDDS and share of food in total household expenditure	57.0%	4892 households
[105]	Anambra state	Households living in Ukpo, Ichida, and Awka	To examine food security status, associated factors, and coping strategies employed by households in Anambra state	The findings indicated that large households and those whose mothers had only primary or secondary education were more likely to be food insecure	Survey (Cross-sectional)	USDA HFSSM Approach	61.0%	657 households
[106]	Nigeria	Households in rural and urban Nigeria	To examine the food security status of households during the COVID-19 pandemic in Nigeria	The findings revealed that 12% of the households were food secure, with 88% in varying degrees of food insecurity	Secondary data: COVID-19 National Longitudinal Phone Survey (COVID-19 NLPS)	FAO’s FIES Approach	88.0%	1821 households
[107]	Enugu state	Households in Enugu	To determine the food security status and its predictors among households in Enugu state	The results showed that major factors influencing the food security status of households include wealth index and cooperative society membership	Survey (Cross-sectional)	Adapted freedom from hunger or food security scale	61.1%	800 households
[108]	16 states	Smallholder maize and rice farming households in 192 communities	To examine the roles of women’s empowerment and how land tenure property rights (LTPRs) influence household food security among farmers in Nigeria	The findings showed that households that have a share of farmland on purchase and who also participate in off-farm activities are likely to be food secure	Survey (Cross-sectional)	USDA 18-question HFSSM Approach	74.5%	1152 households
[109]	7 northern states	Farmers in 84 rice-growing communities	To examine LTPRs among smallholder rice farmers in northern Nigeria and their influence on household food security.	The results revealed that land titling is not endogenous in the estimated models, and that household food security is largely enhanced with an increase in shares of freehold and leasehold in the households’ farmlands	Survey (Cross-sectional)	USDA 18-question HFSSM Approach	73.9%	547 farmers
[29]	Nigeria	Rural households in Nigeria	To assess the dynamics of food insecurity among rural households in Nigeria using panel data	The results revealed that 44% of households that were food secure in the first panel transited into food insecurity in the second panel, while 32.5% that were mildly food insecure transited into food security	General Household Survey (GHS) cross-sectional panel data	HFIAS Approach	64.9%	3022 rural households
[110]	Nigeria	Rural households in Nigeria	To assess the dynamics of food insecurity among households in rural Nigeria	The study revealed that food insecurity status increased with large family size, dependency ratio, being female-headed, and ageing household heads	General Household Survey (GHS) cross-sectional panel data	HFIAS Approach	First panel: 36.9%; Second panel: 53.5%	3022 rural households
[46]	Ogun state	Maize farmers	To assess food security and its drivers among maize farming households in Ogun state	The study showed 23.2% food insecurity, while 5.5% and 1.8% of households were found to have depth and severity of food insecurity, respectively	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach (food security line = NGN 2643.66)	23.2%	250 households
[111]	Oyo state	Cassava farming households	To assess food insecurity among farming households in rural Oyo state	The results revealed that 12.8% of the farming households were food secure, while 87.2% had varying levels of food insecurity	Survey (Cross-sectional)	HFIAS Approach	87.2%	211 households
[112]	Oyo state	Households having under-5 children in Ibadan	To evaluate household food security and nutritional status of under-5 children in Ibadan, southwestern Nigeria	The study showed that even though households may be above the severe hunger status, the quality of the diet may be insufficient to provide needed nutrition for the health security of household members, especially under-5 children	Survey (Cross-sectional)	HFIAS Approach	63.0%	707 households (Mothers with under-five children
[113]	Nigeria	Adult Nigerians	To identify factors associated with financial insecurity, food insecurity, and poor quality of daily lives of adults in Nigeria during the first wave of the COVID-19 pandemic	The study reported that 2487 (56.0%) were financially insecure, 907 (20.4%) had decreased food intake, and 4029 (90.8%) had their daily life negatively impacted	Online survey (Cross-sectional)	Food intake	90.8%	4439 households
[40]	Nigeria	Rural and urban Nigerian adults	To assess the impact of the COVID-19 lockdown on economic and behavioural patterns related to food access.	The study revealed that even though smaller households had higher food expenditure claims than larger households, the larger the household, the more serious the challenge of economic access to food	Online survey (Cross-sectional)	FIES Approach	42.3%	883 households
[114]	Kwara state	Farming households	To evaluate the effect of climate-smart agricultural practices (CSAP) on the food security of farming households in the Kwara state	The results revealed that crop rotation is the most used CSAP in the study area, and that 16.7% of the respondents are low users, 53.33% medium users, and 30% high users of CSAP	Survey (Cross-sectional)	Food Insecurity Index (per capita food expenditure) Approach	41.1%	90 farming households
[115]	Gombe and Osun states	6–19-year-old school-aged children	To assess the associations between household food insecurity, dietary diversity, and dietary patterns with the double burden of malnutrition	The results indicated that the median dietary diversity score was 7.0. Two dietary patterns (DPs) were identified. Traditional DP was significantly associated with both thinness and overweight/obesity	Survey (Cross-sectional)	HFIAS Approach	47.3%	1200 participants
[116]	Plateau state	Households in 3 communities of Langai district	To assess the level of food security and its sociodemographic determinants among rural households	The results showed that significant predictors of household food security include women earning more than the basic monthly wage, those without marital partners, smaller household sizes, and those not receiving financial support	Survey (Cross-sectional)	Food Consumption Scores (FCS)	21.4%	201 households
[117]	Nigeria	Nigerian households	To examine the interrelationship among gender, empowerment, and households’ food security status in Nigeria	The findings indicated that the level of empowerment is generally low in Nigeria (21.63%), but it is much worse among the female gender (11.78%)	Secondary data: a cross-sectional dataset from the 2018/2019 Living Standard Measurement Survey	Dietary diversity score	31.1%	4979 households
[60]	Nigeria	Nigerian households	To examine perceived changes in food security as well as finances and revenue of rural and urban households during the Covid-19 pandemic in Nigeria	The study revealed that the COVID-19 pandemic has worsened the food security situation of both rural and urban households and that it has also adversely affected rural and urban household finances	Secondary data: Nigeria COVID-19 National Longitudinal Phone Survey	3-question household food insecurity	83.0% (urban); 78.0% (rural)	1950 households
[61]	Nigeria	18 years and above adults	To assess if there were significant differences in the adoption of COVID-19 risk-preventive behaviours and experiences of food insecurity of people living with and without HIV in Nigeria	The results revealed that, in comparison with those living without HIV, PLWH had higher odds of cutting meal sizes as a food security measure and lower odds of being hungry and not eating	Online survey (Cross-sectional)	Adapted USDA HFSSM (2-question)	29%	4471 participants
[118]	Adamawa, Akwa Ibom, Anambra, Benue, Kaduna, Lagos, Enugu, Nasarawa, Gombe, and Niger states	Women and girls living with or at high risk of acquiring HIV	To advance understanding of the economic impact of COVID-19 on WGL&RHIV and to identify the factors associated with food insecurity	The findings revealed that being a member of the key and vulnerable groups was strongly associated with food insecurity, financial vulnerability, and housing insecurity, regardless of HIV status	Survey (Cross-sectional)	Adapted 1-question food security approach	76.1%	4355 respondents
[119]	Anambra, Ebonyi, and Enugu states	Selected households from the 3 states	To access the perceived effect of the COVID-19 pandemic on food security in southeast Nigeria	The study found that the percentage rate of food consumption of the households before the pandemic was higher relative to the COVID-19 event	Survey (Cross-sectional)	Recommended daily calorie required approach	75.6%	209 households
[120]	Nigeria	Nigerian rural and urban households	To examine the joint influence of land access and the gender of the household head on household food insecurity	The results showed that female-headed households (FHHs) are more food insecure than male-headed households	General Household Survey (GHS) cross-sectional panel data	Self-assessment measure of household food consumption	Male: 23.7%; female: 43.1%	4581 households
[121]	Enugu state	Male and female household heads in three LGAs (Oji River, Enugu East, and Uzo-uwani) of Enugu state	To assess the household food and nutrition security among households in Enugu state	The study indicated that the FGT model results for the headcount ratio showed only 22% of households were food secure during the COVID-19 pandemic	Survey (Cross-sectional)	Recommended daily calorie required approach (2100 kcal)	78.0%	480 households
[122]	Oyo, Ekiti, and Ogun states	Rural farming households in the three states	To evaluate the determining factors of rising food expenditure, implications for food security, as well as households’ coping strategies during the COVID-19 pandemic	The study indicated that the FGT model results for the headcount ratio showed only 22% of households were food secure during the COVID-19 pandemic	Survey (Cross-sectional)	Recommended daily calorie required approach (2100 kcal)	78.0%	480 households
[123]	Rivers and Bayelsa states	Farming households in the Niger Delta region	To investigate how vulnerability to the “triple challenge” affects food security among farming households in the Niger Delta region	The results revealed that vulnerability to the “triple challenge” increases the probability of being in a severe food insecure state, particularly for households with a high dependency ratio	Survey (Cross-sectional)	FIES Approach	72.2%	503 households
[19]	Ogun and Oyo states	Smallholder cassava farming households	To investigate food insecurity, health and environment-related factors, and agricultural commercialization among smallholder farm households	The findings revealed that less than 20%, 30%, and 40% of households in all four food insecurity categories had access to piped water, improved toilet facilities, and electricity, respectively	Survey (Cross-sectional)	HFIAS Approach	90.9%	352 households
[124]	Oyo state	Smallholder gari processors	To evaluate food security status and highlight survival strategies used by gari processors in Oyo state	The findings revealed that none of the gari processing households in Oyo state were found to be food secure	Survey (Cross-sectional)	USDA approach: 18-question HFSSM	100%	120 gari processors
[125]	Niger state	Preschool children	To assess the household food security and feeding patterns of preschoolers in Niger state, Nigeria	The study showed that 59.8% of the preschoolers met their minimum dietary diversity, but 98.8% of the children were from food insecure households	Survey (Cross-sectional)	HFIAS Approach	98.8%	450 participants
[126]	Kogi state	Cashew farming households	To assess the household food insecurity status of cashew farming households in Kogi state	The study indicated that food security status was determined by household size, farming experience, education level of households, annual off-farm income, output of cashews, and output of cereals	Survey (Cross-sectional)	Recommended daily calorie required approach	58.8%	228 participants
[41]	Benue, Delta, Ebonyi, and Kebbi states	Nutritionally vulnerable smallholder households	To investigate the effects of COVID-19 on food security and dietary diversity of households in Nigeria	The results showed that income losses due to the COVID-19 restrictive measures had pushed households into more severe food insecurity and less diverse nutritional outcomes	Phone survey	FIES Approach	Pre-COVID-19: 43.0%; During COVID-19: 93.1%	1031 households
[127]	Oyo, Lagos, Abuja, and Plateau states	Households representing different income groups	To examine the impact of the COVID-19 pandemic on food security and psychosocial stress among households in selected states in Nigeria	The study revealed that variables like gender, educational level, and work hours per day were associated with food security and hunger due to COVID-19	Survey (Cross-sectional)	Modified FIES Approach	95.8%	412 households
[128]	Nigeria	Nigerian rural and urban households	Nigerian rural and urban households	The study revealed a significant increase in the prevalence of food insecurity in Nigeria during the COVID-19 crisis	COVID-19 National Longitudinal Phone Survey (NLPS)	FIES Approach	Pre-pandemic period: 36% Period of COVID-19: 74.0% (2nd wave), 72.0% (4th wave)	1674 households
[129]	Northeastern Nigeria	Rural households	To analyze the food security status of rural households in northeastern Nigeria	The results showed that more than half of the selected households were food secure in both waves, but not so in the case of DDS	General Household Survey (GHS)	Mean per capita food expenditure (MPCE) and DDS	MHs, 41.3%; FHs, 84.6% (wave 2); MHs, 38.3%; FHs, 61.7% (wave 3)	902 households

3.1. Common Features of the Reviewed Studies

The first two included scholarly papers in this study were conducted in 2006 [57,62]. Most of the studies in subsequent years (2007, 2009–2019) had research articles ranging from 1–5. According to this review, the trend changed in 2020; this was occasioned by the emergence of the COVID-19 pandemic, which resulted in an increase in the number of scholarly papers published in subsequent years. Many of these papers include review articles, editorials, conference proceedings, books, and chapters in books. In 2020–2022, 11, 13, and 15 articles were included in this review, respectively. The number of respondents ranged in size from the smallest study (with 72 respondents) [101] to the highest-population study (using secondary data) of 5198 respondents [98].

About 17% (13) of the studies utilized secondary data sources [29,40,60,61,85,98,104,105,110,113,117,120,128] within five years (2018, 2020–2023). The first research article that employed a secondary data source was published in 2018 [85]. About 84% (66) of the studies used primary data in investigating and measuring FI in Nigeria. Three notable states in Nigeria with the highest number of FI studies (using primary data) were conducted in Oyo (15), Ogun (10), and Enugu (9), respectively (see Figure 3). According to this review, it is worth noting that no research works (employing primary data sources) were conducted in three states in northwest Nigeria; namely, Jigawa, Katsina, and Zamfara states. According to recent Cadre Harmonise data surveys (2018/2019 household survey), the northwest and the northeast were the two regions having the most acute levels of FI in Nigeria [130]. The southwest had the highest number of FI research studies (45) conducted in the region, while the south–south had the least (9) FI research studies conducted in the region, and only three were reported in Federal Capital Territory (FCT), Abuja (see Figure 3). Furthermore, about 9% (7 articles) of studies in this review employed qualitative methodology [68,76,87,101,103,113,118], while the remaining 91% (72) studies were quantitative in nature. Apart from the survey nature of the studies, some (five studies) incorporated focus group discussion (FGDs) and key informant interviews (KIIs) [59,72,82,83,97].

Figure 3. The Nigerian map showing the geographical distribution of the 66 research studies.

3.2. Quantifying Food Insecurity

Sixty-three (80%) of the studies included in this review employed the most common FI measurement tool (Figure 4). The commonest method of measuring FI was through HFIAS, with eighteen studies [19,72,74,77,81,84,89,90,91,93,95,110,111,112,115,121,125]. The FI prevalence measured through the HFIAS module ranged from 36.9%, reported from a study that investigated the dynamics of FI using secondary data collected in 2010/2011 and 2015/2016 among households in rural Nigeria [110], to 98.8%, reported in research of household FI and feeding patterns of preschool children in north–central Nigeria [125]. Apart from [125], seven other studies reported a prevalence of FI that is above 90%; for instance, [80] (93.5%), [96] (92.8%), [102] (92.7%), [113] (90.8%), [19] (90.9%), [41] (95.8%), and [127] (95.8%).

Figure 4. FI measurement tools employed in the studies included in this systematic review.

Furthermore, twelve studies utilized the HFSSM approach. For instance, refs. [67,94] used 10-item and 16-item forms of HFSSM, while other studies [57,70,80,96,97,100,105,107,108,124] used the conventional full 18-item module. The use of the minimum recommended daily calorie required per adult equivalent is another common method for measuring FI in Nigeria in recent times. Thirteen studies utilized it, while three studies [50,83,122] utilized the same minimum value of 2100 Kcal for their studies in the southwestern and north–central states of Nigeria. Studies by [47,48] utilized 2260 Kcal from Kwara and Oyo states, respectively. Other studies used different daily calorie requirements; for instance, both [88] and [62] used 2250 Kcal, while [71] used 2500 Kcal; ref. [75] used 2550 Kcal; ref. [68] used 2470 Kcal; and ref. [49] utilized the highest value of 2710 Kcal. Also, ref. [126] utilized a 2145 Kcal per capita calorie intake, while [119] used three minimum recommended calorie benchmarks of 2100 Kcal, 1800 Kcal, and 2700 Kcal in their study, which focused on the perceived effects of COVID-19 on food security in southeastern Nigeria. Furthermore, an approach through the per capita food expenditure of households was used in ten studies. Apart from this method, ref. [129] added other methods, such as dietary diversity score (DDS) and Foster–Greer–Thorbecke (FGT), while [104] only added DDS to their study using nationally representative data from the National Bureau of Statistics (NBS).

Additionally, it was observed that studies that employed the “mean per capita food expenditure” approach used varying food security lines (FSL) for which households were categorized as either food secure (if the households met the threshold of a two third mean per capita food expenditure) and food insecure, if otherwise. For instance, refs. [46,66,73,79,86,92] had food security lines of NGN 7967, NGN 1948, NGN 4219, NGN 2643, NGN 10,704, and NGN 20,132 respectively. Furthermore, [114] specified an FSL of NGN 2900 for their study that focused on the effects of climate-smart agricultural practices on food security among farming households in Kwara state, while [99] did not specify the FSL used in categorizing the households into food secure/food insecure households in their study. Furthermore, seven studies employed the FIES approach. Out of these five were COVID-19-related studies in Nigeria [40,41,106,127,128], while two studies were not related to COVID-19 [39,123]. All of the COVID-19-related studies reported that household food access was hampered by the COVID-19 lockdowns in many parts of Nigeria. The study by Samuel et al. [40] reported that lockdown restrictions increased food expenditure and experiences of FI among the respondents. Meanwhile, ref. [106] utilized the COVID-19 National Longitudinal Phone Survey (COVID-19 NLPS) and found that 58.5% of Nigerian households experienced severe FI. Using the standard eight-item FIES in their study, ref. [41] found that only 6.9% of the Nigerian households were food secure, while emphasizing the inadequacies or non-existence of safety net programs, which further plunged the households into severe food insecurity during the pandemic. The study of Bwala et al. [127], which captured the psychosocial stress factors amid COVID-19, reported an increasing level of aggression and irritation among all categories of households, but this was greater among the low-income earners of the selected households in southwest and north–central Nigeria. Out of the 1674 households used in the study by [128] using the COVID-19 NPLS, about 4% were severely FI in the pre-pandemic, but they recorded 43% severe FI during the COVID-19 pandemic.

The method of using the food consumption score (FCS) in measuring FI was not quite popular among the studies included in this review. Only two studies used FCS [85,116]. The investigation by [116] using the FCS and coping strategy index (CSI) found that 21.4% of the households were quality-food insecure, while 34.8% were economically vulnerable to FI. The study by [85] did not report the FI prevalence rate among the polygamous family structure in Nigeria but found polygamous households having better food security outcomes than monogamous households using nationally representative data collected in three waves (2011, 2013, and 2015). In Figure 3, the category “Others” referred to FI measurements that were characterized by FI proxies, adapted versions of some other methods, and less popular methods of measuring FI in the Nigerian studies included in this review. Some studies (for instance, [61,78,98]), employed two-item, three-item, and four-item questions to assess FI among the participants, respectively. The three-item version of the HFSSM was adapted by [60,82]. Also, ref. [102] utilized a nine-item food security questionnaire for older children to evaluate the effectiveness of health education intervention on food security and other factors among adolescent girls in Maiduguri, Borno state, while [68,107] adapted the “Freedom from Hunger scale” (FFH) in assessing households’ FI status in Enugu state [131]. The study by [59] adapted the “Household Hunger Scale” (HHS) by [132] and DDS for assessing household food and nutrition security in Ohafia matrilineal society in Nigeria and found a 66% FI level among the households. The Dietary Diversity Score (DDS) was also used by [117] among households using nationally representative data; in addition, ref. [103] employed income level, education, and government policy in investigating farming households’ food security in northern Nigeria. The study by [101] employed perception of the food security situation in the prevailing year (2019) to assess the FHHs in Enugu East Senatorial zone of the state, while [113] used changes in food intake as influenced by COVID-19 in exploring FI among residents in Nigeria during the first wave of COVID-19. The use of FI risk perception and management strategies was utilized by [87] in assessing FI among households in Oyo and Osun states and reported 87.6% FI prevalence. The work of [76] employed food habits and coping strategies among the elderly in Ogun state, while [118] adopted a self-reported one-item question “Since the COVID-19 crisis began, do you eat less or skip meals because there was no enough money or food” [133] to investigate the effects of COVID-19 on FI and other factors among women and girls living with or at risk of HIV in Nigeria and reported 76.1% FI prevalence. The food availability pillar of food security measurement was the focus of the study of [120], which also adopted a one-item self-reported question [134], “do you reduce the size of meal eaten in the household because of insufficient food,” among female-headed households and reported 43.1% prevalence of FI among them.

3.3. Exploring Food Insecurity in Different Settings

The studies reviewed were carried out in diverse populations in Nigeria. Thirteen studies investigated FI using the Nigerian public [29,40,60,61,85,98,104,106,110,113,117,120,128]. Among these studies, three utilized online surveys with a state-wide population. Three studies also employed COVID-19 NLPS, while seven studies used secondary datasets from the General Household Survey (GHS) made available through NBS. Twenty-seven studies were carried out among farming households in different population groups in different states. The work of [47] measured FI among farming households in Kwara state and reported 38% FI prevalence. The study of [67] used farming households in Ekiti state and reported about 88% FI, while [69] was carried out among urban farm households in Abuja with 30% FI recorded. Other studies were carried out among farming households in southwestern Nigeria; for instance, [99] (Ogun and Oyo), [46] (Ogun), [81] (Ondo), [122] (Oyo, Ekiti and Ondo), [19] (Oyo and Ogun), [79] (Ondo and Ogun), and [124] (Oyo). Also, some studies were carried out among farming households (crop and livestock) in northern Nigeria. For instance, refs. [88,89,100,103,109] reported 37%, 73.9%, 54.5%, 73.5%, and 81.5% FI. Studies involving farming households in the southeast include [96,101]. Also, ref. [123] carried out their study among farming households in the Niger Delta region (Bayelsa and Rivers states) employing the FIES method and reported 72% FI. Two studies reported on people (women and adolescent girls) living with or at risk of the human immunodeficiency virus (HIV) [84,118] and found 72% and 76% FI, respectively. Further studies reported on primary and secondary school children [57], preschool children [125], and households with under-five children [112] and found a higher percent of FI—76.3%, 98.8%, and 63%, respectively. Ukegbu et al. [94] reported research on university undergraduate students, while [103] was about school-aged adolescents, and they found 93% and 81% FI, respectively. Bwala et al. [127] reported on households with varying income groups during COVID-19 and found about 96% FI.

4. Discussion

This review has investigated the depth of FI research publications in Nigeria over the last seventeen years, cutting across the six regions of the country with diverse populations, including under-five children, people living with or at risk of HIV, rural and urban farm households, and preschool to university undergraduate studies. Nigerian researchers have employed diverse tools to investigate the prevalence of FI. These tools included tested and proven HFIAS, HFSSM, and FIES and unpopular and less dependable one-item and two-item tools. It is of great concern that a sizable number of the studies employed FI proxies, unproven measures, and studies that presented unclear FI methodologies coupled with no information about the actual prevalence rate of FI at different population levels. With different tools identified in the studies included in this review, some of the common FI tools include HFIAS, HFSSM, recommended daily calorie requirement, and the food security index. The studies that utilized the HFIAS module had an FI ranging from 45.8% [90] to 98.8% [125]; studies employing HFSSM reported a range of FI from 37% [100] to 100% [124], and studies that measured FI through the recommended daily calorie requirement ranged from 23.5% [48] to 78% [122].

Many studies were conducted and published in almost every region of the country, but it was quite surprising that no food-(in)security-related research that met the inclusion/exclusion criteria for this review was included (found) from three states in Nigeria: Jigawa, Katsina, and Zamfara states (northwest region) (see Figure 3). Meanwhile, the northwest region is one of the two regions (northwest and northeast) reported in the 2018/2019 household survey and analyzed to have the highest acute (crisis level) levels of FI in Nigeria [130]. Many FI and hunger-related studies are solicited from two regions that are characterized by high levels of hunger, food insecurity, poverty, armed banditry, Boko Haram insurgency, kidnapping, and cattle rustling [14,17,133,134].

Furthermore, the South–South region, with a total of nine studies (see Figure 3), highlights a significant research gap in understanding and measuring food insecurity among the populations in this region. The region is known for incessant incidents of crude oil spillage, with attendant deleterious impacts on the environment that exposed the communities to the problem of household FI, especially among the vulnerable groups (women and children). For instance, ref. [134] reported that 97% of the households in the oil-spill-affected communities in Bayelsa were food insecure when compared to 67% in the control communities. This emphasizes the need for more quality research on food (in)security in the region. Studies that employed the use of a minimum recommended daily calorie requirement per adult equivalent were not consistent with the use of a unified recommended calorie required per adult equivalent. The minimum recommended calories of the thirteen studies ranged from 1800 Kcal [119] to 2700 Kcal [49]. There is a need for a single minimum recommended calorie to be used in determining FI among different settings. Also, the Nigerian government, through its agencies and other relevant non-government agencies, may propose a unified minimum recommended calorie to be used in any food-security-related studies in the country.

Some studies utilized single-item to three-item tools to measure FI prevalence at household and national levels. However, as indicated in this review, the quantification of FI using one-item to three-item studies, with questions including “if anyone reduces the size of meal in the household because of insufficient food” and “cut the size/skip a meal,” found that FI ranged from 25% among people living with and without HIV in Nigeria during COVID-19 [62] to 43.1% among FHHs in Nigeria [120]. Comparing the prevalence rate of FI using one-item to three-item tools with other broad and extensive measures [19,80,124] revealed that the use of one item might have underrated the prevalence of FI in Nigerian studies included in this review. This finding was corroborated by the studies from Australia, which opined that the use of a one-item measure underestimated the prevalence of FI by about 5% when compared with more extensive tools [135,136,137,138,139]. Furthermore, some studies in this review used small sample sizes where the results of the studies may not be generalized; for instance, refs. [47,101,114]. It is worth noting that two studies from this review failed to report the prevalence rate of FI after data description and analyses [71,85]. The FI prevalence rate (usually reported in percent) is an important indicator of the food insecurity level or status in a population and, as a matter of compulsion, it should be reported in the published studies. Among seven studies included in this review that employed qualitative methods of analyzing FI, [76] reported the lowest FI prevalence rate of 12%, assessing the food habits of the elderly in Ogun state. Also, through a qualitative method, ref. [113] reported the highest level of FI (90%) among adult Nigerians during the first wave of COVID-19. This review indicated that 71% of the studies that measured FI through qualitative methods used FI proxies, such as income level, education attainment, food insecurity risks, food habits, and government policy [76,87]. Meanwhile, studies that quantified FI through quantitative methods used well-recognized and standardized FI tools, such as HFIAS, HFSSM, and FIES [12,39,109]. Surprisingly, the work of [124] was the only study that reported 100% FI in this review, while the study was carried out among gari processing households in Oyo state.

4.1. Limitations of This Study

This review contained some limitations that should be mentioned. It is important to acknowledge the effort made to ensure that this review was extensive, but it is possible that some studies might have been omitted, especially those that might have been published after the database search was concluded. It is worth noting that this review is the first systematic review of FI investigation and quantification in Nigeria. With different kinds of FI measurement tools and diverse approaches employed by different studies, it was quite challenging juxtaposing the outcomes of various studies. This review is also limited to studies (articles) extracted from the stated research databases, while some other studies not indexed in these databases were not included. Nevertheless, the authors do not feel that the lack of a meta-analysis should undermine the validity of the findings in this study.

4.2. Areas for Further Research

The issue of food insecurity is a global phenomenon, although the African region is experiencing the highest burden in recent times. A systematic review of this nature may be extended as an African study to have a comprehensive understanding of food insecurity and quantification of food (in)security research endeavours in the region.

5. Conclusions

According to the authors’ search, this is the first systematic review that assesses the comprehensive nature of food security studies conducted in Nigeria. This study revealed different approaches employed by researchers in gathering important details about food insecurity in Nigeria. These approaches included standardized FI measurement tools, adapted measures (one-item to three-item questions), and FI proxies. The one-item to three-item questions were found to present an underrated or underestimated prevalence of FI among different populations in the country. With different FI tools used by researchers in this review, it is quite difficult to comprehend the correct or accurate prevalence and gravity of FI in Nigeria. While some studies found FI prevalence as low as 12 to 21.4% [76,115], a study reported a 100% FI prevalence among gari processors in Oyo state [124]. As revealed by the investigation of this review, the authors highlight the need for a measurement tool that would be appropriate for Nigerian settings and that would enable researchers to attain comprehensive knowledge of the FI prevalence and severity in the country, paving the way for improved food- and nutrition-sensitive policy development.