Food insecurity and obesity: research gaps, opportunities, and challenges

While the link between food insecurity and obesity are well documented in the research literature, more research is needed to better understand underlying mechanisms, associated risks, effective strategies and interventions, and implementation science approaches to mitigate these public health concerns.

Abstract

Food insecurity, defined as a lack of consistent access to enough food for an active, healthy life, is a major public health concern with 11.8% of U.S. households (15.0 million) estimated to be affected at some point in 2017 according to the United States Department of Agriculture Economic Research Service. While the link between food insecurity, diet quality, and obesity is well documented in the literature, additional research and policy considerations are needed to better understand underlying mechanisms, associated risks, and effective strategies to mitigate the adverse impact of obesity related food insecurity on health. With its Strategic Plan for NIH Obesity Research, the NIH has invested in a broad spectrum of obesity research over the past 10 years to understand the multifaceted factors that contribute to the disease. The issue of food insecurity, obesity and nutrition is cross-cutting and relates to many activities and research priorities of the institutes and centers within the NIH. Several research gaps exist, including the mechanisms and pathways that underscore the complex relationship between food insecurity, diet, and weight outcomes, the impacts on pregnant and lactating women, children, and other vulnerable populations, its cumulative impact over the life course, and the development of effective multi-level intervention strategies to address this critical social determinant of health. Challenges and barriers such as the episodic nature of food insecurity and the inconsistencies of how food insecurity is measured in different studies also remain. Overall, food insecurity research aligns with the upcoming release of the Strategic Plan for NIH Nutrition Research and will continue to be prioritized in order to enhance health, lengthen life, reduce illness and disability and health disparities.

Implications.

Practice: This research can provide evidence of effective programs or strategies to reduce food insecurity or obesity related to food insecurity that can be integrated into practices in the real-world setting.

Policy: Food insecurity and obesity are serious public health challenges and research related to programs, policies, and/or environmental strategies could be considered to reduce risk factors associated with food insecurity patterns and promote sustainable approaches for healthy food access, especially among the most vulnerable.

Research: To address gaps in food insecurity and obesity research, the National Institutes of Health supports a broad-spectrum of biomedical and behavioral research that seeks to identify underlying mechanisms, associated risks, and effective strategies to mitigate this public health concern.

INTRODUCTION

Food insecurity—a lack of consistent access to enough food for an active, healthy life—is a significant global and domestic public health concern. An estimated 11.8 per cent of American households were food insecure at some point during 2017 [1]. About 4.5 per cent of households had very low food security, a more severe range of food insecurity in which the food intake of some household members was reduced, and normal eating patterns were disrupted at times during the year due to limited resources. Overall, rates of food insecurity were higher than the national average in low-income households, Black- and Hispanic-headed households, and households with children [1].

A negative association between food insecurity and health has been consistently demonstrated in the literature [2]. Among children and adolescents, food insecurity has been associated with a variety of outcomes such as asthma [3], anemia [4], and behavioral, academic, and emotional problems [5]. Among adults, studies have shown that food insecurity is associated with poor dietary quality [6], depression [7], cardiometabolic diseases [8], diabetes and poor diabetes control [9] and obesity, particularly among adult women [8, 10, 11]. The question of whether food insecurity causes obesity was first published in 1995 [12]. Since then, the body of evidence exploring this relationship has grown substantially. Despite several hypotheses that have been proposed in the literature to explain the link between food insecurity and body weight, it is not well understood if food insecurity plays a causative role in the development of obesity, and if it does, what mechanisms are involved [10].

Food insecurity, nutrition, and obesity are cross-cutting scientific topics that are within the National Institutes of Health (NIH)-supported research, however, are often not examined in tandem within individual studies. This research is facilitated across several Institutes and Centers to progress toward reducing chronic diseases; understanding genetic, behavioral, and environmental causes; and studying impacts of innovative prevention and treatment strategies designed to address them. The NIH and other funding agencies have made investments in this area of research; however, additional studies are needed to better understand underlying mechanisms, associated risks, and effective strategies to mitigate these public health concerns. Furthermore, the NIH has the opportunity and ability to promote translational research and implementation science to adequately address issues of food security and obesity within the U.S. population.

The purpose of this commentary was to consider the challenges, gaps, and opportunities in the research exploring the link between food insecurity and obesity. In this commentary, we:

• Describe the food insecurity and obesity research within the various NIH Institutes and Centers;

• Identify key fundamental challenges with how food insecurity is defined;

• Explain research gaps ranging from the need for more research and potential strategies to explore the continuum of research from the mechanisms and pathways of the relationship to more longitudinal and multilevel intervention research; and

• Highlight research opportunities through existing funding mechanisms and epidemiological cohort studies and future research stemming from the Strategic Plan for NIH Nutrition Research.

NIH-wide investments

With its Strategic Plan for NIH Obesity Research, the NIH has invested in a broad-spectrum of obesity research over the past 10 years to understand the multifaceted factors that contribute to the disease [13]). The issues of food insecurity, obesity, and nutrition are cross-cutting and relate to many funded research studies throughout the Institutes and Centers within the NIH. There is also a specific focus within the NIH to promote implementation science and study the methods and strategies that enhance the uptake of effective interventions into routine practice with the aim of improving population health [14]. From fiscal years (FY) 2009–2017, the most recent year for which complete data were available, the NIH funded 30 grants, related to food insecurity and obesity (NIH RePORTER tool, search terms “food insecurity” or “food desert” + RCDC code = “obesity”, fiscal years 2009-2017, awarded grants only). The NIH spent $31.6 million from FY09 to FY17 on these grants. Eight (27 per cent) of these grants were funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Other major funders included the National Institute of Diabetes and Digestive and Kidney Diseases (five grants, 17 per cent), the National Cancer Institute (four grants, 13 per cent), the National Heart, Lung, and Blood Institute (three grants, 10 per cent), and the National Institute on Minority Health and Health Disparities (three grants, 10 per cent). The majority (22; 73 per cent) of these grants were research project grants, whereas 3 (10 per cent) used training mechanisms, and the remainder were intramural or other.

Prominent thematic and topical areas covered by the most recent grants, identified using the NIH iSearch tool, include maternal stress, food stamps, pediatric obesity, and corner or convenience stores. Studies ranged from secondary data analysis of existing datasets to community-based interventions to change individual-level dietary behaviors and food insecurity outcomes. For example, one study explored the influence of stress on household food insecurity and dysregulated eating behaviors on weight among women postpartum [15]. Formative research from a community-based participatory research study, Tribal Health and Resilience in Vulnerable Environment Study, assessed for correlates of food insecurity within an Oklahoma tribal community to inform development of a community-based intervention within convenience stores to increase the availability of fruit and vegetables [16]. This research included practical applications to expand the impact of the research. For example, the partnerships formed as a result of the study informed policies used to address the issue of food insecurity, including the development of a community supported agriculture and community food program, increased access to culturally appropriate produce at local farmers' markets, restructuring the placement of healthy foods in local grocery stores, and the introduction of Electronic Benefits Transfer (EBT; the method for which Supplemental Nutrition Assistance Program, the largest federal food assistance program, is redeemed) [16] (Fig. 1).

Fig. 1.

The National Institutes of Health (NIH)-funded grants on food insecurity and obesity, 2009–2017, by the NIH Institute/Center. “Other” category includes National Institute of General Medical Sciences, National Institute on Alcohol Abuse and Alcoholism, National Center for Complementary and Integrative Health, National Institute on Aging, and National Institute of Nursing Research. Each Institute/Center in the “Other” category funded one grant. Abbreviations: NICHD, Eunice Kennedy Shriver National Institute of Child Health and Human Development; NIDDK, National Institute of Diabetes and Digestive and Kidney Diseases; NCI, National Cancer Institute; National Institute of Mental Health; NHLBI, National Heart, Lung, and Blood Institute; NIMHD, National Institute on Minority Health and Health Disparities; NIMH, National Institute of Mental Health.

Research challenges and barriers

Despite investments by the NIH and others in this area, key challenges and barriers remain, particularly on the accuracy of measurement, definitions, and operationalization of the food security measure. Although there is variation in how food security is assessed across the literature, most studies in U.S. population use instruments that are based on the United States Department of Agriculture (USDA) Food Security Supplement, which is administered annually in conjunction with the Census Bureau's nationally representative Current Population Survey. The Food Security Supplement includes a series of 18 questions (10 questions if no children are included in the household) that ask respondents about their experiences over the past 12 months related to concerns that food would run out, perceptions about the quantity and quality of the meals they could afford, and whether any adults or children had to forgo food due to a lack of resources. A validated 6-item “short form” has also been created by the USDA for surveys that cannot implement the 18-item or 10-item questionnaire [17]. Instruments used in the literature range from a single question to all 18 items [8]. In addition to the instrument developed by the USDA, a review by Ashby et al. [18] identified eight other multi-item tools that were used to assess food security in developed countries. These tools were shown to have moderate-to-high internal consistency but varying levels of validity among the subpopulations at risk for food insecurity [18].

The severity and duration of exposure to food insecurity can be difficult to quantify. This is due in part to the heterogeneous circumstances of food-insecure individuals and a range of situations that can fluctuate throughout the year causing many households to cycle in and out of food insecurity [8, 19]. Categories of food insecurity include marginal food security, low food security, and very low food security; however, current measurement tools do not distinguish between acute and chronic food insecurity and may not adequately capture information in vulnerable subgroups (i.e., among non-English speakers) or the nuance of the experience of food insecurity among different cultures, for example, among immigrant populations [20, 21]. In addition, the USDA metric of food insecurity primarily focuses on the economic definition of food insecurity and does not capture behavioral coping patterns such as the trade-offs between food purchases and other expenses [22]. There are few longitudinal surveys that assess food insecurity at multiple time points or over the life course. These limitations create a challenge when evaluating the relationship between food insecurity and health outcomes, such as obesity.

Another research challenge comes from the fact that many studies measure food insecurity at the household level, which may not accurately reflect the degree of food insecurity experienced by any one individual. Studies in the international context suggest differences in intra-household food allocation based on gender and age [23]. For example, children in a food-insecure household may be shielded from the impact of a food shortage by their parents, and thus, will not be affected by food insecurity to the same extent as an adult living in the same household [24]. Even among food-insecure adults, there may be a large variation in the severity of the food insecurity that they experience. This variation is difficult to capture and may explain some of the mixed results in the literature.

Research gaps

To explore the state of the research in this area and identify predominate research gaps, we examined the existing literature and systematic reviews on the topic. Four main research gap areas emerged (Table 1) including: (a) the mechanisms and pathways underlying the relationship between food insecurity and obesity; (b) the impact of food insecurity on pregnant and lactating women, children, and other vulnerable populations; (c) longitudinal studies; and (d) effective multilevel intervention strategies that could be used for greater real-world impact.

Table 1.

Research gaps and direction for future research

Topic	Research gaps and opportunities
1. Mechanisms and pathways	• Underlying mechanisms and pathways that explain the relationship between food insecurity and obesity and contradictory findings in the literature based on demographic groups • Research drawing from the intersection of evolutionary biology, ecology, and obesity literature
2. Impact on pregnant and lactating women, children, and other vulnerable populations	• Short- and long-term impact of food insecurity on weight outcomes among pregnant and lactating women, infants, children, and adolescents • Impact of food insecurity and dietary patterns on the onset and progression of chronic diseases such as obesity and diabetes • Influence of food insecurity across the life course and critical periods of development • Influence of food insecurity on racial/ethnic and rural/urban health disparities
3. Longitudinal studies	• Well-designed longitudinal studies to support the temporality criteria for Bradford Hill's criteria for causality and explore pathways, mechanisms, and dietary patterns underlying this relationship
4. Effective multilevel intervention strategies	• Strategies that integrate several aspects of the socioecological model for change (individual, organizational community, policy, etc.) • Interventions that target federal food and nutrition programs (i.e., SNAP and WIC) and their recipients • Natural experiment studies that leverage federal and local policy changes that influence food insecurity • Interventions that use electronic and other innovative technologies

Mechanisms and pathways

Although the link between obesity, food insecurity, and diet has been examined, the research literature shows conflicting results depending on the subpopulation and dataset used [11, 25, 26]. The varying effects and contradictory findings that differ by gender, race, ethnicity, and age group warrant further exploration. Future research should also explain the underlying mechanisms and pathways underscoring this relationship and contradictory findings.

Previous research has posited that food insecurity contributes to irregular eating patterns characterized by periods of underconsumption and food deprivation when resources are limited, and compensatory overconsumption when resources are adequate, contributing to adiposity [27–29. Coupled with this cycle is the widespread availability of high calorie, low-cost foods consumed by those experiencing food insecurity. Theoretical models have proposed a mechanistic explanation drawing in findings from the intersection of evolutionary biology, ecology, and obesity research [10, 30]. Yet, the driving mechanisms remain unclear.

Impact on pregnant and lactating women, children, and other populations

Given the critical role nutrition plays in fetal and childhood development, additional research exploring the long-term impact of food insecurity on pregnant and lactating women, and during infancy, toddlerhood, and adolescence are still needed [8, 31]. Understanding the influence of food insecurity patterns on the onset and progression of chronic diseases such as obesity and diabetes and its influence across the life course and critical periods of development are of particular interest. Existing studies show food insecurity in pregnancy and postpartum to be associated with disordered eating, variations in gestational weight gain depending on prepregnancy weight [15, 32], and decreased duration of breastfeeding [32]. In addition, as previously stated, most of the literature measures food insecurity at the household level and extrapolates these data to represent the childhood experience, meanwhile children may be protected from the influence of food insecurity due to intra-household food allocation strategies (i.e., a mother feeding her children before herself to shield her children from food insecurity) [8, 23].

Examining the consequences of food insecurity at different stages of child and adolescent development is also important. For instance, one study found that infants and toddlers from low-income households that had food insecurity were at significantly greater developmental risk (in areas such as language, motor, and socio-emotional development) than those from low-income households without food insecurity [33]. Another study showed that in a large sample of U.S. adolescents, food insecurity was associated with greater risk of mental disorders, after controlling for other socioeconomic (SES)-related variables, such as extreme poverty [34]. Understanding how food insecurity affects development across the lifespan is key to informing both interventions and policy approaches for particular segments of the population.

Additional research among other diverse and vulnerable populations is also a priority to ensure that the knowledge and evidence base and results are relevant, reliable, and valid in these populations. Food insecurity, for example, affects a greater proportion of racial/ethnic minority and socially disadvantaged groups in the USA that are already at increased risk for diseases related to diet such as heart disease, stroke, and diabetes. Typically, such populations are underrepresented in research studies and are considered hard to reach due to a lack of responsiveness to interventions that are designed for general audiences within dissemination and implementation research [35]. However, there are broader levels of influence to be understood such as the role of inadequate outreach and engagement, insufficient capacity or infrastructure within these communities, use of culturally unacceptable research methods, and in some populations, low participation due to various issues, including historical mistrust [35, 36]. Examining food insecurity in rural and urban settings and coping strategies people use to mitigate consequences of food-related hardship in each context is also important and will assist in unraveling these complex associations [37, 38]. Improving our understanding of food insecurity among diverse population groups will ultimately help to design interventions and pragmatic approaches to address these known health disparities. By expanding knowledge related to the specific barriers, moderators, and mediating pathways of each group, successful interventions can be better designed and implemented through targeted screening and referral programs or the establishment of new food distribution programs or innovative partnerships.

Longitudinal studies

Because of the complexity of the relationship between food insecurity, diet, and obesity, additional cross-sectional analyses are limited in their ability to answer key research questions. For example, cross-sectional studies cannot establish directionality of associations between food insecurity and obesity. In addition, researchers can statistically control for a variety of sociodemographic factors such as income, education, and race to consider the influence of these factors on both weight and food insecurity, but other unmeasured variables related to food insecurity (i.e., timing, duration, and coping strategies) cannot be accounted for in cross-sectional studies. Although longitudinal studies present similar concerns of unmeasured confounders, the time sequence of events can be clarified with this approach. To the best of our knowledge, there are very few longitudinal studies that explore this area [39, 40].

More innovative longitudinal evidence is thus a priority. These studies would elucidate the issue of timing and temporality and support an important criterion for causality as well as shed light on the long-term effect of food insecurity on diet and weight status. In addition, well-designed longitudinal studies would allow for the exploration of the pathways and mechanisms underlying this relationship, which is also critical. Although causality cannot be confirmed given the limitations of longitudinal studies, the inability to conduct conventional randomized control trials to examine this issue should also be acknowledged [41]. Instead, comparative effectiveness studies offer another alternative to explore these associations.

Development of effective multilevel intervention strategies

Given the systems and social factors that contribute and perpetuate food insecurity and the complexity of the issue, the development of innovative multilevel interventions strategies to address obesity among those experiencing food insecurity is an additional priority. Existing interventions mainly focus on low-income families participating in federal food and nutrition programs (i.e., Supplemental Nutrition Assistance Program (SNAP) and Special Supplemental Nutrition Program for Women, Infants and Children (WIC) and have targeted individual-level behaviors, such as diet and physical activity [42–44]. A more policy-focused initiative includes the USDA-funded Healthy Incentives Pilot, which evaluated the short-term impact of financial incentives to purchase fruit, vegetables, or other healthful foods on the diet quality of SNAP participants [45]. Because of the pilot nature of the study, the long-term impacts on weight outcomes were not explored. However, this pilot program and other USDA-funded incentive programs have led to permanent funding in the 2018 Farm Bill in what is called the Gus Schumacher Nutrition Incentive Program, providing opportunity for future research and evaluation [46]). Meanwhile, relatively few intervention studies have considered the influence of the various elements of food and nutrition programs (i.e., amount and timing of EBT benefit, and length of time on benefits) on reducing the risk of obesity in their design. Meanwhile, research suggests that these factors may have implications in the link between food insecurity and food programs and obesity [47, 48], and therefore should be examined further.

Novel methods that leverage natural experiments or evaluation of the influence of large-scale programs and policies on food access (i.e., policy changes resulting in reductions in EBT benefits) and health outcomes should be explored. It is also important to examine how food environments affect food insecurity and improve the ability to collect more granular geographic data to quantify better local or small area variation of food environments and accessibility to healthy, affordable food resources. These data could improve research efforts related to various disease outcomes and help identify contextual features that may facilitate or hinder successful implementation of intervention strategies. For example, the differential impacts of interventions in rural and urban environments are of interest. In addition, leveraging of electronic and other technologies to address issues of food insecurity are also opportunities for future research growth.

Research opportunities

Current funding opportunity announcements

Recognizing the need for more research to explore the link between obesity and food insecurity and effectively address these concerns, the NIH is currently seeking innovative applications to address these research gaps. In addition to supporting investigator-initiated grant applications through parent funding opportunity announcements (FOAs), the NIH solicits potential projects related to food insecurity and obesity through three targeted funding opportunity announcements. PAR-18-854, “Time-Sensitive Obesity Policy and Program Evaluation (R01 Clinical Trial Not Allowed)” supports research to evaluate programs and policies that target obesity-related behaviors and/or weight outcomes in an effort to prevent or reduce obesity. It also uses an expedited review and award process to support time-sensitive evaluation of programs or policies with imminent implementation. PA-18-032, “Understanding Factors in Infancy and Early Childhood (Birth to 24 months) That Influence Obesity Development (R01 Clinical Trial Optional)” seeks applications that propose research to identify or characterize factors from birth to 24 months that affect obesity risk in children, a key demographic vulnerable to the effects of food insecurity.

Current and former cohorts available for analysis

A few large current and former NIH studies have included the assessment of household-level food insecurity among study participants, which provides the potential for future research studies on the topic. For example, launched in 2015, the Environmental Influences on Child Health Outcomes Program is a 7-year initiative to understand the effects of environmental exposures on children's health [49]. Through the synergistic study of multiple extant longitudinal cohorts, researchers are collecting food insecurity measures, as well as data on physical, chemical, biological, social, behavioral, natural, and built environments on child health outcomes, such as obesity [49]. The Healthy Communities Study, conducted between 2010 and 2016, is another NIH-funded study that collected dietary data and a food insecurity measure [50]. The goal of the study included the examination of community characteristics and how these relate to children's dietary and physical activity behaviors, and health outcomes, particularly childhood obesity. The diverse cohort represented 130 communities and over 5,000 children and their families in the USA [50]. Ultimately, these cohorts include measures that would support the development of research to strengthen our understanding of the impact of food insecurity on the weight status of children over time.

The Strategic Plan for NIH Nutrition Research

The upcoming release of the Strategic Plan for NIH Nutrition Research will continue to prioritize research to expand our understanding of the link between food insecurity and obesity. In October 2016, Dr. Francis Collins, the Director of NIH, established an NIH Nutrition Research Task Force to coordinate and accelerate progress in the NIH-funded nutrition research and to guide the development of the first NIH-wide Strategic Plan for Nutrition Research. Through a collaborative process of gathering information across the various Institutes, Offices, and Centers within the NIH and from the external nutrition research community, literature searches, and public crowdsourcing opportunities, the NIH identified research gaps and areas of opportunity to prioritize the future of nutrition research. The culmination of these efforts is the Strategic Plan for NIH Nutrition Research, which will serve as a guide to accelerate basic, translational, and clinical research, as well as research training activities, over the next 10 years. The Plan is organized by seven themes that each contain major research priorities and examples of related research activities. Equally important to the identification of evidence-based nutrition strategies to improve health is the translation of this research into practice so that health-care providers, patients, families, caregivers, and communities are equipped with tools to adapt and sustain successful nutrition practices. Therefore, the Plan specifically prioritizes efforts to expand implementation science (i.e., the study of methods to promote the adoption and integration of evidence-based practices, interventions, and policies into routine health care and public health settings to improve the impact on population health).

A need for further research related to the direct and indirect consequences of food insecurity and how these consequences alter nutrition and health relationships is highlighted in the Strategic Plan. How food insecurity and other social determinants of health and environmental factors contribute individually and in combination to interindividual variability in the relationships between diet and health requires further elucidation. In addition, research areas aimed at determining the mechanisms underlying the co-existence of food insecurity, obesity, and other related metabolic conditions are described.

The Strategic Plan also calls for increased efforts in systems science and advancement in bioinformatics and computational approaches in nutrition research. As these approaches continue to advance, new opportunities to evaluate the systemic factors and relationships that affect and are affected by nutrition are emerging and may offer opportunities to expand research capabilities. Such approaches may help to untangle the pathways and mechanisms associated with the complex relationships between food insecurity, diet, and weight status or other health outcomes that are difficult to investigate. Insights provided by this research may provide new opportunities for interventions to address food insecurity and related health consequences.

Translational implications

Beyond the topics identified as challenges and gaps for food insecurity and obesity in this article, there is the importance of putting research into practice to positively affect the 11.8 per cent of American households who face food insecurity every year in the USA. As mentioned, implementation science plays an important role in identifying barriers to, and enablers of, effective health programming and policymaking, and leveraging that knowledge to develop evidence-based innovations in effective delivery approaches. It is important for researchers to go beyond studying outcomes for effectiveness and begin systematically targeting implementation outcomes as well. This would include outcomes such as acceptability, adoption, appropriateness, cost, feasibility, fidelity, penetration, and sustainability that are key in the effective translation of evidence-based outcomes into any population [51].

Identifying which intervention studies are effective and testing approaches to scale up and sustain these interventions will therefore be critical in the decades to come. For example, should food insecurity screenings be implemented in the dissemination of SNAP benefits? Could interventions be implemented through the SNAP-Ed or are there other settings that are practical for dissemination, such as the clinical setting? Providers across the health-care setting, for example, screen for food insecurity, but providers need a way to connect their patients to resources that best address the specific needs of their patients. Conducting implementation studies and addressing food insecurity from a multidisciplinary platform may help to identify critical partnerships and technologies or capacity solutions that will increase uptake of evidence-based practices and ultimately reduce food insecurity among American households.

CONCLUSION

This commentary highlights the gaps in the literature examining the association between food insecurity and obesity, former and current efforts within the NIH to address these gaps, and future research opportunities. Although the link between food insecurity and obesity are well documented, additional research and policy considerations are needed to better understand underlying mechanisms, associated risks, and effective strategies to mitigate these public health concerns. The relationship between food insecurity and obesity is at a critical juncture that could greatly benefit from the utilization of translational research and implementation science to effectively shape the field to create lasting change and results. The use of multidisciplinary teams from food insecurity, obesity, and an array of other fields is essential for the understanding and targeting of the problem. Research is needed to test effective approaches and scale up these interventions into diverse contexts to adequately address obesity among those who experience the varying levels of food insecurity. Current funding opportunity announcements focusing on obesity, particularly among children, are potential vehicles for funding in this area. The upcoming release of the Strategic Plan for NIH Nutrition Research and its future implementation is yet another opportunity to expand research to better understand the mechanisms underscoring the link between food insecurity and obesity and more importantly develop effective translatable behavioral interventions to address this important social determinant of health.

Funding

This commentary was not funded.

Compliant with Ethical Standards

Conflict of Interest: All authors declare they have no conflicts of interest.

Ethical Approval: Human rights, informed consent, and animal welfare ethical statements are not applicable.

Disclaimer: The views expressed in this manuscript are those of the authors and do not necessarily represent the views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development; the National Heart, Lung, and Blood Institute; National Institute of Diabetes and Digestive and Kidney Diseases; the National Institute on Minority Health and Health Disparities; the National Institutes of Health; or the U.S. Department of Health and Human Services.

Primary Data: Data presented in the portfolio analysis of this manuscript is from NIH RePORTER.