Background

Indigenous peoples of the United States disproportionately experience chronic diseases associated with poor nutrition, including obesity and diabetes. American Indian and Alaska Native (AIAN) preschool children have the highest prevalence of obesity compared to other racial/ ethnic groups (37.0% among AIAN compared to 17.4% among non-Hispanic whites) [1]. Disparities persist into adulthood, and recent reports indicate that the prevalence of obesity among AIAN adults is approximately 80% higher than among non-Hispanic whites and Asians [2]. Furthermore, although the prevalence of obesity appears to have leveled off in other ethnic and racial groups, the prevalence continues to rise among AIAN people [3, 4]. Consistent with obesity rate, the prevalence of diabetes is considerably higher in AIAN (17.9%) than in non-Hispanic whites (7.9%) [5].

While chronic disease related health disparities among AIAN people are well documented, it is unknown whether interventions adequately address these health disparities. In addition, it is unknown whether and to what extent interventions are culturally adapted or tailored to the unique culture, worldview and nutrition environments of AIAN people. Genuine and equitable partnerships between researchers and AIAN communities are critical to ensuring that interventions are relevant. Community based participatory research (CBPR) is considered best practice for conducting research with AIAN communities [6, 7]. Using a CBPR approach that draws on the traditional knowledge of communities can engender strength-based interventions that reinforce cultural continuity and have broad positive impacts. For example, programs seeking to strengthen the traditional food system have the potential to address high prevalence of chronic disease in addition to promoting food sovereignty. These traditional practices also provide a foundation for cultural identity, a basis for social support networks, and assist Indigenous Peoples in gaining greater autonomy [8].

While involvement of the community at every step of the process in intervention planning and implementation in Indigenous groups has been widely noted to be important in promoting adequate dietary intake, not all programs have involved engagement with community members. Examining and characterizing interventions that have involved community engagement to various degrees may prove useful for researchers and educators planning to implement programs in Indigenous communities. The primary objectives of this systematic review were to: 1) Identify and characterize nutrition interventions conducted with Indigenous populations in the United States; and 2) To determine whether and to what degree communities are involved in the design, implementation, and evaluation of the intervention.

Methods

Peer-reviewed journal articles were identified using the online database MEDLINE.

Study inclusion and exclusion criteria

To be included in the review, research articles had to 1) be published in a refereed journal between 2000 and 2015; 2) report on a diet-related program or intervention conducted in an Indigenous population in the United States; 3) report outcome data. Studies that were reported in a language other than English, reported on process data only, and review papers were not included.

Search strategy

The following two overarching concepts were identified to guide selection of search terms and phrases based on the review objectives: Indigenous populations and chronic disease prevention/health promotion. For the first key concept, related terms and phrases identified were: ‘Hawaii/ethnology,’ ‘Native Hawaiian,’ ‘Indians, North American,’ ‘American Indian,’ ‘Native American,’ ‘Native Alaskan,’ ‘Oceanic Ancestry Group/ethnology.’ For the second key concept, search terms and phrases were as follows: ‘diabetes mellitus/education,’ ‘diabetes mellitus/prevention and control,’ ‘chronic disease/prevention and control,’ ‘nutritional sciences/education,’ ‘obesity/prevention and control,’ ‘health promotion,’ ‘overweight/prevention and control,’ ‘cardiovascular diseases/prevention and control,’ ‘wellness,’ and ‘intervention.’ Boolean operators such as AND and OR were used to link search terms.

Using the search terms, one researcher (JB) identified abstracts for review. Referencing the inclusion criteria, the same researcher examined the abstracts and excluded studies not meeting the requirements for inclusion. The same procedure was followed with the full papers identified using the abstracts remaining. Finally, for all full papers included, a search was conducted for other papers reporting on the same study by searching for the title of the intervention and examining the references in each paper. This search was conducted to address the fact that many papers reporting outcomes do not report on the steps involving community engagement. While one goal of the review was to characterize interventions and thus gauge the effectiveness of programs through outcomes reported, it was also imperative to capture community involvement through examination of all papers related to each study. Figure 1 illustrates the search strategy used for this review.

Fig. 1
figure 1

Flow Diagram Illustrating Selection of Studies for Systematic Review of Community Involvement in Design, Implementation and Evaluation of Nutrition Interventions in Indigenous Populations in the U.S

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Data extraction

After obtaining consensus on the abstraction tool, two researchers (JB, AB) piloted the tool on two studies to reach agreement on the procedures for data abstraction. One researcher (JB) then conducted a systematic review of full studies identified and completed the abstraction table. Data entered in the abstraction table included the following: study objectives, target population/inclusion criteria, study design, study setting (city, state), study duration, sample size, response rate, intervention (focus and main activities of the program), outcome variables, measures utilized, involvement of the community in the design, implementation, and evaluation of the intervention (formative research to inform design and evaluation, partnership, community capacity building, involvement of local food system), treatment length/follow up, drop out, results, main implications, and limitations.

Data synthesis

Table 1 contains a list and description of the 49 studies identified in the literature search. Within these 49 studies, there were 39 distinct programs, given that the outcomes of some programs were described in multiple publications.

Table 1 List and description of the 49 studies identified in the literature search
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Quality appraisal of studies

Study quality was assessed using the Effective Public Health Policy Project (EPHPP) Quality Assessment Tool. The EPHPP Quality Assessment Tool provides criteria to evaluate studies on the basis of selection bias, study design, confounders, blinding, data collection methods, withdraws and dropouts, intervention integrity, and analysis. Each criterion is scored numerically according to the guidelines as strong (score = 1), moderate (score = 2), or weak (score = 3). Subsequently, the entire article is rated as strong (no weak ratings), moderate (one weak rating), or weak (two or more weak ratings).

Results

Program objectives

Program objectives varied. Four focused on reducing BMI, one focused on increasing physical activity, five focused on improving diet or food behaviors, six focused on improving knowledge/awareness and/or self-efficacy, five focused on improving other health outcomes (e.g., Hgb A1c, blood pressure, cholesterol), and 18 studies had multiple objectives.

Program activities

All programs had a nutrition education component. Seven also focused on changes to the physical environment (Table 1). For example, an obesity prevention trial in American Indian children incorporated changes to foods served in the school setting to reduce calories [9]. In another study in Native American high school youth, an existing room in the high school was remodeled into a fitness center [10]. Twenty-nine programs included a physical activity component in addition to the dietary component.

Target populations

Sixteen programs focused on groups suffering from a chronic condition, such as overweight/obesity or diabetes. Twenty-four programs focused exclusively on adults, seven programs focused exclusively on children, and seven programs included a wide age range. Nineteen studies focused exclusively on American Indian populations. Seven studies included AI and/or AN in addition to one or more ethnic groups. None focused on Alaska Native populations exclusively. Information on the target population is reported in Table 1.

Geographic region

With regards to geographic region, two programs were conducted in the Northeast, six in the Midwest, three in the South, 22 in the Western region, and six in more than one region of the US.

Formative research to inform design

Twenty-five programs reported conducting formative research to inform the design of the intervention, although the nature and duration of the formative research varied. While in some cases investigators relied on literature review or review of existing data to inform design, in most cases, the community was directly involved in this step. Formative activities included interviewing or conducting focus groups with members of the target population for guidance regarding the content, format, and method of delivery of the intervention, pilot testing of the intervention in the community, and review of the curriculum by the community. For example, the Strong in Body and Spirit program in Native Americans involved focus group sessions in the community that allowed members to express their desire for inclusion of traditional foods and values [11]. The types of formative research used to inform design of the intervention in each study are displayed in Table 2.

Table 2 Strategies used in nutrition interventions conducted in Indigenous populations in the US: Formative research to inform design
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Formative research to inform evaluation

Five programs identified included formative research to inform evaluation of the intervention. These activities included collaborative work of the research team with the community to identify outcome measures, as well as examination of evaluation instruments by members of the target population to ensure relevance. For example, for the Healthy Living in Two Worlds project conducted in urban Native youth, a draft of the instrument to be used to assess knowledge, attitudes and behaviors related to tobacco use, dietary practices and physical activities was evaluated by several Haudenosaunee youth to insure that the questions were clear and meaningful to this particular population [12]. The types of formative research used to inform evaluation of the intervention in each study are displayed in Table 3.

Table 3 Strategies used in nutrition interventions conducted in Indigenous populations in the US: Formative research to inform evaluation
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Partnership

Twenty-eight programs involved a partnership between researchers and the community. Such partnerships involved collaboration with the target population on data collection, collaboration with local organizations or establishments, development of a community action plan with the target population, delivery of the intervention by members of the target population, holding regular meetings with the target population, and collaboration with the tribal review board or ethics committee. For example, in a type 2 diabetes prevention intervention in Native American communities, program staff networked with local agencies to share information and resources to inform the intervention [13]. The types of partnerships formed in each study are displayed in Table 4.

Table 4 Strategies used in nutrition interventions conducted in Indigenous populations in the US: Partnership
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Capacity building

Twenty-one programs included some aspect of capacity building among project staff and community members in their programs. Examples of capacity building included training community members to perform health-promoting practices, use of “train the trainer” sessions, joint development of a community action plan, formation of local working groups, and promotion of career development of project staff. For example, several studies used community peer educators to deliver lessons that formed part of the intervention [14, 15]. The types of capacity building that were part of each study are displayed in Table 5.

Table 5 Strategies used in nutrition interventions conducted in Indigenous populations in the US: Capacity building
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Involvement of local food system

Sixteen programs incorporated some aspect of the local food system into the intervention. This included involving local food service or local food retailers in the intervention, as well as incorporating local foods into the educational materials and/or activities programs. For example, in an after-school intervention of urban Native American youth, discussion of the importance and roles of traditional foods of the group under study formed part of lessons provided [16]. The types of involvement of the local food system in each study are displayed in Table 6.

Table 6 Strategies used in nutrition interventions conducted in Indigenous populations in the US: Involvement of local food system
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Outcomes

Thirty–one programs of the 39 programs (79%) identified reported significant changes in knowledge, behavior or health (Table 1). In terms of the degree of community involvement in the studies reporting significant changes in outcomes, all except one program included at least one of the five strategies examined in this review regarding community engagement, and 19 used at least three out of the five strategies (Table 1). For example, the Cancer 101 program employed formative research to inform the design of the program in working with tribal health directors to review the curriculum, demonstrated partnership with organizations that had established relationships with tribal communities and involved capacity building in the form of train the trainer sessions [17]. In further examining the studies reporting significant results, five were RCTs, 24 were pre-post studies, one had a multiple cross-sectional design, and one was a retrospective study.

Study quality

Twelve studies were rated as strong, 13 studies were rated as moderate, and 14 studies were rated as weak according to the EPHPP Quality Assessment Tool.

Discussion

Results of the current literature review yielded research studies conducted with a variety of objectives in diverse Indigenous groups throughout the US. Overall, interventions were successful in producing changes in knowledge, behavior or health. The degree to which communities were involved in the design, implementation, and evaluation of the intervention varied from not at all to involvement at all stages. Of the programs reporting significant changes in outcome measures, more than half used at least three strategies to engage communities. The extent of use of strategies to promote community engagement in programs reporting significant outcomes is notable.

While formative research to inform the design of the interventions was performed in most studies, formative research to inform the evaluation was not performed to a great degree, with only six programs identified including this step. In some of these cases, researchers worked with the community to determine what outcomes should be measured, a process that enhances the program’s alignment with traditional values. In particular, following an indigenous evaluation framework, as described by LeFrance and colleagues, ensures that programs pay sufficient attention to the cultural context in which behaviors arise, thereby increasing the potential success of interventions [18]. In other cases, members of the target population provided input on the content of evaluation tools and participated in pilot testing. Previous research has revealed the importance of this step and has outlined procedures that may be used to determine face validity of instruments [19], as well as other procedures that should be conducted to evaluate the psychometric properties of evaluation tools [20]. It is essential that evaluation tools are designed in collaboration with the target audience to ensure relevance [20]. Given that very few studies identified in this review involved formative research to inform evaluation, it is possible that not all relevant outcomes were reported. While results were often presented in terms of changes in weight and diet, there may be other outcomes such as cultural connectedness that may be important for the communities in question but were not measured.

Fewer than half of the programs identified described involvement of the local food system. In further seeking to promote health in Indigenous communities, incorporation of local foods is an important consideration. Working in concert with local food retailers or other establishments may allow for the inclusion of traditional foods in the intervention. In communities in which people identify themselves with their culture and natural environment, use of traditional food systems to improve health builds community support and engagement for holistic health and well-being [21]. Factors contributing to obesity and diabetes in Indigenous people are complex, and are rooted in dietary Westernization that leads to significant changes in food sources and nutrient intake [22]. In Indigenous communities, participating in the traditional food system is linked to higher diet quality, lower levels of chronic disease risk factors, lower levels of stress and overall well-being. The traditional diet of Yup’ik People in Southwestern Alaska, for example, is rich in vitamin D, vitamin A, vitamin E, iron, and n-3 fatty acids through inclusion of foods such as fatty fish, fish roe, seal oil and wild game [22]. Similarly, the traditional diet of Native Hawaiians has been found to be high in fiber, polyunsaturated fatty acids, and low in fat and cholesterol [23]. Over the past century, Indigenous food systems have been compromised as a result of social, economic, political and environmental pressures [24]. The consequences of the transition away from nutrient-rich traditional food in Indigenous communities include shifts in nutrients intake, obesity and associated diet-related chronic conditions [25,26,27]. In a study of Pima Indians in Arizona, for example, intake of complex carbohydrate, dietary fiber, insoluble fiber, vegetable proteins and the proportion of total calories from complex carbohydrate and vegetable proteins were significantly higher in the Indian than in the Anglo diet [28]. Intervention activities must work in concert with the local cultural and social settings, local personnel and local sources of food [21].

The majority of programs were carried out in the Western region. Of note, of the studies conducted in this region, relatively few were focused on populations in Alaska and Hawai’i. As Indigenous groups in these states face health disparities, future studies may further focus on these geographic areas. Among Native Hawaiians, for example, the prevalence of chronic diseases constituting the leading causes of death in the U.S.—heart disease, cancer, and diabetes—is notably high [29]. Rates of diet-related chronic conditions such as cardiovascular disease are also high in Alaska Natives [30]. Other researchers have pointed to the need for individual-level interventions for behaviors related to obesity in groups such as Native Hawaiians [29].

Also of note, most programs focused exclusively on adults. As particular nutrition-related burdens fall on youth, children continue to be an important target group in further addressing issues related to diet in Indigenous groups. According to data from the National Health and Nutrition Examination Survey (NHANES), 17% of children and adolescents in the U.S. were obese in 2011–2014 [31]. Previous studies indicate that the diet quality of children and adolescents in the U.S. falls short of the recommendations, and that diet quality may be improved by increased intake of foods such as vegetables, whole grains and seafood [32]. Good nutrition is essential for child growth and development, as well as for maintenance of a healthy weight [33].

Ten of the interventions identified were randomized controlled trials, and half of these reported significant results. Most studies used a pre-test, post-test design. Without a control group, such studies do not provide the same level of evidence as the RCT and do not allow conclusions of the same caliber to be drawn [34]. However, given that research in Indigenous populations may be performed in small, geographically dispersed samples, it may not always be feasible to conduct a RCT. Studies with a pre-test, post-test design may provide evidence to inform additional studies in the population of interest. Of note, there were a number of studies rate as “weak” with regards to study quality. These ratings reflected issues such as failure to report withdrawals and drop-outs, as well as lack of assessment of validity and reliability of data collection tools. Failure to report withdrawals and dropouts leads to difficulty in determining the degree to which participants engaged in the intervention and the effects of the program, as evaluation of all participants enrolled in the program may not have been possible. In other cases, it was not possible to ascertain whether the outcome assessors were aware of the intervention or exposure status of participants or if the study participants were aware of the research question. These issues may have compromised study results to varying degrees. If, for example, outcome assessors were aware of the intervention or exposure status of participants, this may have led them to alter their behavior toward participants or perform measurements differently in the two groups. In cases in which less than 100% of participants received the allocated intervention, it is possible that there may have been systematic differences between those who completed the intervention and those who did not, compromising the results of the study.

With regards to program activities, relatively few programs involved changes to the physical environment. However, of those that did, all found significant results, and five out of the seven studies also involved used of at least three strategies to engage communities. Other researchers have noted the need to design interventions at multiple levels, including individual, social environmental, physical environmental, and macrosystem [35]. While all of the programs identified in this review had a nutrition education component, a change in health outcomes may not result without concomitant environmental changes. In planning future interventions, this is an important consideration.

Limitations

While not all studies made use of the strategies identified in this review to engage communities, it should be noted that not all studies focused exclusively on Indigenous populations. In some cases, the target population was comprised of both Indigenous people and members of other groups. In these instances, it may not have been possible or reasonable to use some of the strategies identified, such as incorporating traditional foods into the intervention. This should be taken into account in examining results. Further, only one database was used to identify articles to include in the review, and gray literature was not examined. Thus, it is possible that some relevant articles may not have been located.

Conclusions

Interventions performed in Indigenous groups in the US were generally successful in producing changes in knowledge, behavior or health. Interventions mostly targeted adults in the Western region and used a pre-test, post-test design. Of the nutrition interventions reporting significant changes in outcome measures, more than half involved notable engagement of communities. The degree of use of strategies to promote community engagement in programs reporting significant outcomes is notable. However, formative research to inform the evaluation was not performed to a great degree, and fewer than half of the programs identified described involvement of the local food system. In planning interventions in Indigenous groups, researchers may consider the range of ways in which the community may be involved in the design, execution and evaluation of the intervention based on the studies reviewed here. Such involvement is likely to improve the success of these initiatives. There is a particular need for studies focused on Indigenous youth in diverse regions of the US to further address diet-related chronic conditions.