Kyoung-Min Lee; EunSeok Cha; Han-Sol Park; Min-Sun Jeon

doi:10.5720/kjcn.2026.00234

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Research Article
Development of a nutrition program for Koreans with type 2 diabetes based on the health belief model: a pre-post intervention study: Kyoung-Min Lee^1),2),*, EunSeok Cha^3),*, Han-Sol Park⁴⁾, Min-Sun Jeon^5),6),†; Korean Journal of Community Nutrition 2026;31(4):309-327.
DOI: https://doi.org/10.5720/kjcn.2026.00234
Published online: August 31, 2026

¹⁾Ph.D. Student, Department of Food and Nutrition, Chungnam National University, Daejeon, Korea

²⁾Ph.D. Student, Major of Glocal Life-Care Convergence, Chungnam National University, Daejeon, Korea

³⁾Professor, Department of Nursing, Chungnam National University, Daejeon, Korea

⁴⁾M.S. Student, Department of Food and Nutrition, Chungnam National University, Daejeon, Korea

⁵⁾Professor, Department of Food and Nutrition, Chungnam National University, Daejeon, Korea

⁶⁾Professor, Interdisciplinary Education Center for the Innovative Next Generation Leaders in Glocal Lifecare, Chungnam National University, Daejeon, Korea

†Corresponding author: Min-Sun Jeon Department of Food and Nutrition, Chungnam National University, 99 Daehak-ro, Yuseong-gu, Daejeon 34134, Korea Tel: +82-42-821-6836 Fax: +82-42-821-3335 Email: dearms@cnu.ac.kr

These authors contributed equally to this work.

• Received: June 23, 2026 • Revised: July 10, 2026 • Accepted: July 22, 2026

This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Abstract
INTRODUCTION
METHODS
RESULTS
DISCUSSION
NOTES
REFERENCES

Abstract

Objectives
To evaluate the effectiveness of a health belief model (HBM)-based nutrition education program in improving dietary behaviors, nutrition knowledge, and self-management among Koreans with type 2 diabetes mellitus (T2DM), and to examine age-related differences and the effects of intervention delivery strategies.
Methods
A pre–post intervention study was conducted among 21 adults with T2DM (glycated hemoglobin levels ≥ 7.5%) attending outpatient clinics at university hospitals in Korea. The HBM-based program incorporated passive learning strategies (lectures and videos) and active, experiential learning strategies. Nutrition knowledge, dietary attitudes, and dietary behaviors were assessed before and after the intervention. Participants’ interest and satisfaction were also evaluated using interest–satisfaction analysis (ISA).
Results
Nutrition knowledge and dietary behaviors improved significantly among adults following the intervention. Adults (n = 15) showed significant increases in nutrition knowledge (0.50 to 0.60, P < 0.05) and dietary behavior scores (2.26 to 2.47, P < 0.05), whereas no significant changes were observed among older adults (n = 6). The mean interest and satisfaction scores were 4.44 and 4.43 out of 5, respectively. Experiential learning strategies were associated with higher satisfaction than passive approaches. ISA showed that hands-on activities received the highest interest and satisfaction ratings, whereas passive methods were rated less favorably.
Conclusion
Participation in an HBM-based nutrition education program was associated with improved dietary behaviors among Koreans with T2DM in a clinical nutrition setting. Experiential learning approaches appeared to be more effective than passive methods, and the age-related differences observed suggest a need for tailored intervention strategies. These findings support the development of scalable, patient-centered nutrition interventions for chronic disease management.
Keywords: diabetes mellitus, type 2; nutrition education; health belief model; dietary behavior

INTRODUCTION

Type 2 diabetes mellitus (T2DM) is a major global public health concern associated with substantial morbidity and mortality due to macrovascular and microvascular complications [1, 2]. According to the International Diabetes Federation, approximately 537 million adults worldwide were living with diabetes in 2021, and this number is projected to increase substantially in the coming decades [3]. The Diabetes Fact Sheet in Korea 2024, published by the Korean Diabetes Association, reported that 5.33 million Korean adults aged 30 years or older had T2DM in 2022. This corresponds to a prevalence of 14.8%, indicating that approximately one in seven adults is affected [4]. Although awareness, treatment, and control rates for T2DM have improved [5], global health care expenditures attributable to diabetes have increased markedly, reaching USD 1.015 trillion in 2024 [3].

The prevalence of prediabetes in Korea is estimated at 41.1% among adults aged 30 years or older, affecting approximately 14 million people nationwide [5]. Given Korea’s rapid transition to a super-aged society, the prevalence of diabetes is expected to continue increasing. T2DM requires lifelong self-management, including medication adherence, dietary regulation, physical activity, and stress management [6-8]. Inadequate disease control may lead to complications, reduced quality of life, and an increased risk of mortality [6-8]. Therefore, active patient participation and sustained self-management are essential components of diabetes care [9].

Patients with T2DM must engage in multidimensional self-management behaviors, including dietary therapy, medication adherence, blood glucose monitoring, and physical activity [8]. Glycemic control is central to T2DM management, and dietary regulation, physical activity, and pharmacotherapy are the primary approaches. Dietary management is fundamental to lifestyle modification, and previous studies have shown that theory-based behavioral interventions can improve dietary behaviors and glycemic outcomes [10, 11]. However, because T2DM requires lifelong management, the sustained effort needed to maintain glycemic control may impose a substantial and persistent burden on patients [12]. Many patients have difficulty maintaining long-term dietary changes despite recognizing their importance [13-15]. Dietary behavior is critical to glycemic control and the prevention of complications [16], but eating habits are deeply established lifestyle patterns and can therefore be difficult to modify [14]. Previous studies have shown that nutrition education can improve glycemic control, dietary behaviors, and adherence to recommended dietary practices among individuals with T2DM [17, 18]. Nevertheless, sustained adherence remains challenging in real-world settings because it requires continuous motivation and considerable behavioral effort. Nutrition education seeks to improve nutrition knowledge, dietary attitudes, and self-management behaviors by providing evidence-based information and practical skills [19]. To maximize effectiveness, interventions should be grounded in behavioral theory and use instructional strategies that promote participant engagement and application in daily life [20-22]. The health belief model (HBM) is a widely used theoretical framework in nutrition education; it proposes that individuals are more likely to adopt recommended health behaviors when the perceived benefits outweigh the perceived barriers [23]. Despite the established benefits of nutrition education for individuals with T2DM, relatively little attention has been given to how instructional media and delivery formats affect learning outcomes and behavioral change. In particular, limited empirical evidence has compared passive educational approaches, such as lectures and videos, with active, experiential learning strategies within theory-based interventions [24, 25]. Age-related differences in responsiveness to educational media also remain insufficiently explored, despite the growing proportion of older adults among patients with T2DM. Understanding how educational strategies can be optimized for age-specific characteristics is essential to improving self-management interventions [26]. In addition, few studies have examined participant engagement across instructional media and educational formats, and interest–satisfaction analysis (ISA) has rarely been applied in diabetes nutrition education. ISA can provide complementary information about participants’ perceptions of educational content and delivery strategies, thereby helping identify components that require refinement. Accordingly, this study extends conventional program evaluation by examining not only the effectiveness of an HBM-based behavioral intervention but also the differing effects of instructional media and learner engagement on educational outcomes. This study therefore aimed to develop an HBM-based behavioral intervention program for T2DM management and evaluate its effectiveness through pre- and post-intervention analyses. The findings are intended to provide empirical evidence for the design of tailored nutrition education interventions in Korea.

METHODS

Ethics statement

This study was conducted in accordance with the Declaration of Helsinki, and all procedures involving human participants were approved by the institutional review boards of Chungnam National University Hospital (CNUH 2021-03-092-009) and Sejong Chungnam National University Hospital (CNUSH 2021-07-009). Written informed consent was obtained from all participants.

1. Study design

This study developed and implemented a behavioral intervention program for patients with T2DM. It used a single-group pre–post intervention design.

2. Development of the behavioral intervention program

The diabetes management education program developed in this study comprised two sessions designed to explain the key concepts and importance of diabetes care. The curriculum used a coherent and balanced pedagogical framework to present the educational objectives clearly. To promote engagement and active learning, the content was structured to stimulate participants’ interest. All materials were tailored to participants’ age, literacy levels, and prior experiences to support accessibility and comprehension (Fig. 1). The program focused on implementing healthy dietary practices among individuals with T2DM. Topics were selected from nutrition education materials relevant to T2DM, and the program was structured to help participants translate the knowledge acquired into behavioral change. In particular, it emphasized practical strategies for adopting and repeatedly practicing desirable health behaviors in daily life. The final program was developed after review by a multidisciplinary team with expertise in nutrition education, clinical nutrition, nursing, and exercise prescription. The educational materials were based on nutrition education methods provided by the Gyeonggi Center for Hypertension and Diabetes (2020) [27] and were refined according to the guidelines of the Korea Health Promotion Institute (2022) [28]. The lesson plans presented concrete, clearly defined educational objectives to facilitate assessment of achievement, and activity difficulty was adjusted according to participants’ interests and capabilities. The HBM served as the theoretical framework for organizing the educational content and activities. To enhance engagement and the practical application of knowledge, the program incorporated PowerPoint presentations, interactive games, videos, and experiential activities. The program was designed not only to provide basic information about appropriate dietary practices but also to motivate behavioral change [29, 30]. Accordingly, experience-based activities were used to integrate key dietary information systematically, and the instructional materials were selected and developed to support application of the curriculum in participants’ daily lives [29, 31].

3. Participants

This study included outpatients diagnosed with T2DM who attended the Department of Endocrinology at Chungnam National University Hospital and Sejong Chungnam National University Hospital in Korea and consented to participate. Initially, 32 participants were recruited. Eligible participants were adults aged 20–75 years who resided in the Daejeon or Sejong area and had glycated hemoglobin levels of 7.5% or higher. The exclusion criteria were type 1 diabetes mellitus (insulin-dependent diabetes), diabetic foot disease, retinopathy, physical limitations affecting use of the hands or feet, and participation in a diabetes education program for more than 1 month during the previous 6 months. To improve accessibility and participation, the program combined face-to-face sessions with sessions delivered in real time through an online platform (Zoom, Zoom Video Communications). Participants primarily received face-to-face education. However, participants who lived far from the hospital or were unable to attend face-to-face sessions because of the COVID-19 pandemic received real-time online education via Zoom instead. The mode of instruction was determined according to participants’ accessibility and circumstances rather than by random assignment. The program was conducted from July 2021 to January 2022.

All participants attended two sessions of the behavioral intervention program at 2-month intervals; each session lasted 40–50 minutes. A total of 32 participants were enrolled. During the intervention, 5 participants withdrew or did not attend the first education session, and 6 withdrew or did not attend the second education session. Data from the remaining 21 participants who completed the intervention were included in the final analysis (Fig. 2). Program effectiveness was assessed using identical survey items and standardized procedures before and after the intervention. Participants’ interest in and satisfaction with the educational content and delivery methods were also assessed quantitatively. Given the outpatient recruitment setting, the intervention was evaluated in a real-world clinical context.

4. Measurements

Data were collected using a structured, self-administered questionnaire tailored to the study objectives. General characteristics included sex, age, educational level, household composition, smoking status, alcohol intake, and frequency of blood glucose monitoring. Household composition was assessed as a multiple-response variable, allowing participants to select all applicable household members. Measures of nutrition knowledge, dietary attitudes, and dietary behaviors were adapted from previous studies to evaluate intervention effects [18, 32, 33]. Effective behavior change in chronic disease management requires theory-based, multicomponent interventions that integrate knowledge, psychosocial factors, and sustained educational support [33]. Nutrition knowledge was assessed using 15 multiple-choice questions. Each item was scored as correct (1) or incorrect, including “don’t know” responses (0), and the mean proportion of correct responses across the 15 items was calculated, with higher scores indicating greater nutrition knowledge. Dietary attitudes and dietary behaviors were each assessed using 12 items rated on a 4-point Likert scale (1 = strongly disagree to 4 = strongly agree), with higher scores indicating more favorable outcomes. Participants’ interest in and satisfaction with the educational content and delivery methods were rated on a 5-point Likert scale ranging from 1 (not at all) to 5 (very much). All instruments were adapted from previously validated measures used in nutrition education and diabetes research, supporting the content validity of the assessment.

5. Statistical analysis

Statistical analyses were performed using IBM SPSS Statistics version 26 (IBM Corp.). Participant characteristics were summarized as frequencies and percentages. Differences in lifestyle-related variables according to age were assessed using Fisher’s exact test. The Wilcoxon signed-rank test was used to evaluate changes in nutrition knowledge, dietary attitudes, and dietary behavior scores from before to after the intervention. Effect sizes were calculated using Cohen’s d for paired samples, calculated as the mean pre–post difference divided by the standard deviation of the paired differences. Participants’ engagement with specific educational content and delivery methods was evaluated descriptively using ISA, and mean interest and satisfaction scores were presented for each educational method.

RESULTS

1. Development of an instructional framework for nutrition education

The behavioral intervention program comprised two sequential sessions, the components of which are summarized in Table 1. The program was developed based on the HBM, which served as the theoretical framework for designing the educational content. The curriculum incorporated key HBM constructs, including perceived severity, perceived benefits, and cues to action, to promote dietary self-management and reduce the risk of diabetes-related complications.

Behavioral strategies and skill-based activities were included to strengthen self-efficacy for behavioral change. Cues to action were also integrated systematically to facilitate the initiation and maintenance of recommended dietary practices and diabetes self-management behaviors.

2. Development of instructional materials

Instructional materials were developed according to the educational themes assigned to each session. Nutrition education cards were created through industry–academic collaboration to enhance learner engagement and motivation. Development involved selecting key thematic terms, determining the number of cards, and designing visual elements aligned with the learning objectives. A professional designer completed the final visual designs to ensure consistency with the educational content.

Each nutrition education card contained four core content elements for each theme. A total of 48 cards were designed for group activities and individual learning. Representative images were created for each keyword, and the cards underwent iterative revision before the final version was approved. Within each thematic category, standard cards had a light-green border, high-priority cards were identified by diagonal shading, and essential key-concept cards were highlighted in yellow to support continued self-directed learning after program completion. Selected card themes are presented in Table 2.

Four instructional videos were also developed to support the behavioral intervention program. The videos addressed the glycemic index (GI), the food exchange system, beverage selection, and sodium reduction (Table 2). They were standardized and used consistently across sessions. Each video was approximately 5 minutes long; the GI video lasted 7 minutes 44 seconds, and the sodium-reduction video lasted 4 minutes 46 seconds.

The GI video used a storytelling format titled “My Traditional Tale: Miho and Dumi” to introduce the GI and the physiological role of insulin. It also presented the “80:20 principle” as an approach to sustainable dietary management based predominantly on healthy food choices while allowing limited flexibility. In addition, the video introduced lifestyle behaviors relevant to diabetes management, including physical activity and routine health checkups.

The food exchange system video provided standardized information on exchange principles and recommended serving sizes for each food group. The beverage-selection video demonstrated the sugar content of commonly consumed beverages and explained how to interpret nutrition labels. The sodium-reduction video presented practical strategies, including reviewing sodium information on labels, using sodium-reducing cooking methods, and adopting daily habits that reduce sodium intake.

Whereas the hypertension-focused sodium-reduction video emphasized quantifiable strategies for reducing sodium intake, the diabetes-focused video used a broader educational approach that integrated physiological explanations and behavioral motivation. This distinction reflects the differing management requirements of hypertension and T2DM.

3. Sociodemographic characteristics of study participants

Among the 21 participants, the largest age group was 55–64 years (42.9%), followed by 65–74 years (28.6%), 36–44 years (19.0%), and 45–54 years (9.5%). Most participants were men (71.4%), and 33.3% had less than a high school education. In terms of household composition, 61.9% lived with a spouse. Most participants were nonsmokers (81.0%), and 52.4% reported consuming alcohol. Blood glucose was most commonly monitored once daily (42.9%) (Table 3).

4. Lifestyle characteristics stratified by age group

Additional analyses comparing lifestyle characteristics by age group showed no statistically significant differences in smoking status, alcohol consumption, or frequency of blood glucose monitoring between adults and older adults (data not shown).

5. Age-stratified evaluation of pre- and post-intervention effects

Among adults, total nutrition knowledge (Table 4) and dietary behavior scores (Table 5) improved significantly after the intervention (P < 0.05). No significant changes were observed in dietary attitude scores (Table 6) or in any outcome among older adults. Item-level analysis showed that, among adults, the proportion of correct responses to the nutrition knowledge item “foods that raise blood glucose the least” increased from 0.47 to 0.87 (P < 0.05). In the dietary attitude domain, the score for the statement “using nutrition labels for dietary management is essential” increased from 3.13 to 3.40. In the dietary behavior domain, the frequency of checking nutrition labels when selecting foods increased from 1.73 to 2.27 (P < 0.05).

Although several items improved significantly among adults after the behavioral intervention program, no statistically significant changes were observed among older adults.

6. Interest–Satisfaction Analysis according to nutrition education content and delivery methods

An ISA matrix was constructed to contextualize these findings (Fig. 3). The overall mean scores of interest and satisfaction, which served as the reference lines for the ISA matrix, were 4.44 and 4.43, respectively. All content domains received mean interest and satisfaction scores above 4.0. Understanding the GI and appropriate consumption of sweet and salty foods were positioned in Quadrant I (Keep it up). By contrast, the three principles of a healthy diet and application of the food exchange system were positioned in Quadrant III (Low priority), whereas management of hypoglycemia was positioned in Quadrant IV (Possible overkill). No items were positioned in Quadrant II (Concentrate here).

For the delivery methods, the ISA matrix results were distributed across all four quadrants. Quadrant I (Keep it up) included several interactive activities: practicing the analysis of Nutrition Facts labels using a handout, assessing dietary habits using a food salinity wheel, making a list of foods appropriate for a diabetic diet based on GI knowledge, and evaluating taste preferences for sweet and salty flavors using a taste sensitivity test. Checking the recommended serving size using food models was positioned in Quadrant II (Concentrate here). In Quadrant III (Low priority), the delivery methods included explaining the three principles of a healthy diet in one's own words using the food balance wheel, practicing the food exchange system using handouts, viewing videos on the glycemic index, dietary sugars, and sodium intake, directly calculating energy intake for weight management, and using dietary cards for memory reinforcement. Finding the dietary card that shows the correct way to manage hypoglycemia and using the handout to identify foods with a low or high glycemic index were positioned in Quadrant IV (Possible overkill).

7. Interest and satisfaction with nutrition education by age group

Interest in and satisfaction with the delivery methods were compared between age groups (Fig. 4). The overall mean interest score was 4.41 among adults and 4.54 among older adults. Although older adults reported greater interest, the difference was not statistically significant. No significant between-group differences were observed for specific media, including PowerPoint presentations, videos, and games, although older adults generally reported higher interest than adults.

The overall mean satisfaction score was 4.45 among adults and 4.46 among older adults, with no statistically significant difference. Experiential learning received high satisfaction ratings in both age groups. Older adults also reported relatively high satisfaction with video-based education.

DISCUSSION

This study applied an HBM-based diabetes behavioral intervention program to 21 patients with T2DM attending outpatient clinic at Chungnam National University Hospital and Sejong Chungnam National University Hospital. It examined age-related differences in educational outcomes and preferences by comparing adults and older adults and evaluated intervention effectiveness based on changes in nutrition knowledge, dietary attitudes, and dietary behaviors in relation to participants’ interest and satisfaction. The findings provide practical insight into the design of effective and engaging nutrition education programs for real-world clinical settings.

After the intervention, adults showed significant improvements in nutrition knowledge and dietary behavior scores, suggesting that the program may have benefited this age group. Older adults, however, showed only limited changes. These differences may reflect age-related factors, including cognitive decline, slower information processing, reduced adaptability to educational media, and the stability of long-established lifestyle habits. This interpretation is consistent with previous studies indicating that older adults may require repeated learning opportunities and longer interventions to achieve meaningful improvements in nutrition knowledge and behavior [34]. The findings can also be considered in light of experiential learning theory, which proposes that knowledge is constructed through active engagement and reflection. Interactive, hands-on approaches may promote deeper cognitive processing and facilitate the translation of knowledge into action.

Age-stratified analyses further showed that total nutrition knowledge and dietary behavior scores increased significantly among adults, whereas participants aged 65 years or older showed only modest improvements. Content difficulty, accessibility of educational media, and differences in comprehension may have influenced these outcomes. Overall interest and satisfaction were high, with mean scores of 4.44 and 4.43 out of 5, respectively. ISA placed the daily-life topic “appropriate consumption of sweet and salty foods” in the high-interest, high-satisfaction quadrant; this topic received the highest interest and satisfaction ratings. Content that is closely connected to everyday dietary practices may therefore promote learner engagement and improve educational effectiveness. By contrast, passive formats such as video-based instruction may be less effective in promoting sustained behavioral change because they rely primarily on information transmission rather than active participation and decision-making.

These findings suggest that experiential learning–based media may promote participants’ interest and satisfaction, highlighting the potential value of active engagement in nutrition education. By contrast, video- and card-based media received relatively lower ratings and were positioned in the lower-performance quadrants of the ISA matrix. Among older adults, card-based games received relatively high interest but comparatively lower satisfaction ratings. This may suggest a mismatch between participants’ expectations and the complexity or comprehensibility of the activities. Simple, intuitive, experiential tools may therefore be more suitable for older adults. Alternative game-based formats, such as low-intensity interactive quizzes, may improve usability and learning outcomes. The findings may also reflect differences in cognitive load, familiarity with educational media, and adaptability to interactive learning environments. More broadly, actively engaging, experience-based strategies may enhance learner satisfaction and perceived relevance and thereby contribute to more effective behavioral change.

Previous studies have shown that nutrition education can produce positive changes in adults and older adults; however, older adults often require longer and repeated interventions to achieve sustained behavioral change [34]. Studies using the HBM have also shown that HBM-based nutrition education can improve nutrition knowledge among older adults and that changes in health beliefs are significantly associated with behavioral intentions [34]. Because T2DM in older adults is associated with progressive complications, patients need accurate disease-related knowledge and lifelong self-management skills [35]. Educational materials should therefore be tailored to individual levels of comprehension, and structured interventions are needed to strengthen self-management capacity [8]. The ISA findings suggest that participants responded positively to hands-on, experiential media, which may promote engagement during nutrition education. Nutrition education is a systematic process through which individuals internalize objective information, develop problem-solving skills, and apply healthy eating behaviors in daily life [19, 22, 36]. Effective programs must therefore consider both the content taught and the methods used to teach it [22]. Nutrition education is commonly defined as a structured intervention intended to improve nutritional status by changing nutrition knowledge, dietary attitudes, and dietary behaviors [36]. Nutrition knowledge comprises accurate information and skills, dietary attitudes reflect willingness to modify eating habits, and dietary behaviors indicate the extent to which such changes are implemented in daily life [37]. Traditional nutrition education has largely followed a Knowledge–Attitude–Behavior framework that emphasizes information delivery and attitude change while giving limited consideration to participant-specific characteristics [36, 38]. To address these limitations, recent interventions have increasingly incorporated behavioral theories such as the HBM to promote sustained change beyond knowledge acquisition [38]. Consistent with previous studies, the HBM-based program developed in this study was associated with improved nutrition knowledge and dietary behaviors among adults. However, because the HBM constructs were not measured directly, the findings should not be interpreted as evidence of changes in specific HBM components [39].

Overall, nutrition knowledge and dietary behaviors improved significantly among adults, whereas changes among older adults were limited. Modifying long-established dietary habits in older adults may require prolonged, repeated educational approaches, consistent with research on nutrition and food-safety education in older populations [36,40]. Such modification may also be difficult because of the complex psychological and social factors that influence diet in later life [40]. Age-related differences should therefore be considered when nutrition education interventions are designed. Future programs may benefit from tailoring instructional approaches to participants’ cognitive characteristics, learning preferences, and educational needs. From an instructional-design perspective, high-engagement, high-satisfaction components should be prioritized, whereas low-impact elements should be reconsidered or redesigned to optimize program effectiveness [21]. Collectively, the findings underscore the need for age-specific behavioral interventions that integrate evidence-based behavioral theories with appropriately designed instructional media.

Limitations

This study has several limitations. First, the small sample and recruitment from a single geographic region (Daejeon and Sejong) limit the generalizability of the findings. Multicenter studies including participants from diverse socioeconomic backgrounds are needed to improve external validity. Second, the intervention consisted of only two educational sessions, limiting assessment of long-term behavioral maintenance and clinical outcomes such as glycemic control. Longitudinal studies with follow-up periods of 3–6 months or longer and repeated educational interventions are therefore warranted. Third, the absence of a control group precludes firm causal attribution of the observed changes to the intervention. Randomized controlled studies are needed to confirm program effectiveness. If short-term outpatient education alone is insufficient to sustain behavioral change, multistage programs incorporating follow-up support by telephone or online platforms should be considered. Finally, although the study used both face-to-face and real-time online instruction through Zoom, the delivery modes were not compared. Future research should examine the differential effects of online, in-person, and blended approaches on learning outcomes. Despite these limitations, the findings indicate that intervention effectiveness may depend not only on content but also on delivery strategies and participant engagement, emphasizing the importance of instructional design in facilitating behavioral change.

Conclusion

In summary, an HBM-based nutrition education program may improve nutrition knowledge and dietary behaviors among adults with T2DM. Participants reported high interest in and satisfaction with experiential activities, indicating the potential value of experiential learning in future nutrition education programs. This pilot study used a single-group pre–post design without a control group to explore program acceptability and preliminary trends in educational outcomes. Nevertheless, the findings support the feasibility and acceptability of implementing an HBM-based nutrition education program in a clinical nutrition setting and provide practical guidance and foundational evidence for future large-scale randomized controlled trials.

NOTES

CONFLICT OF INTEREST

There are no financial or other issues that might lead to a conflict of interest.

FUNDING

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (NRF-2019R1A2C1087199; PI: E. Cha).

ACKNOWLEDGEMENTS

The authors acknowledge the valuable contributions of all participants and staff involved in this study.

DATA AVAILABILITY

The research data are available from the corresponding author upon reasonable request.

Fig. 1.

Development and evaluation process for the behavioral intervention program.

Fig. 2.

Participant recruitment and intervention flow for the behavioral intervention program.

Fig. 3.

Interest–satisfaction analysis matrices for nutrition education attributes by content and delivery method. Each point represents the mean perceived interest score (x-axis) and satisfaction score (y-axis), measured on a 5-point Likert scale ranging from 1 (not at all interested/satisfied) to 5 (very interested/satisfied). The horizontal and vertical reference lines indicate the grand mean scores. (A) In the content-based analysis, the quadrants were defined using a grand mean interest score of 4.44 and a grand mean satisfaction score of 4.43. (B) In the delivery method analysis, the quadrants were defined using grand mean scores of 4.45 for both interest and satisfaction. The matrices were divided into four strategic quadrants: Quadrant I (Keep it up), representing high interest and high satisfaction; Quadrant II (Concentrate here), representing low interest and high satisfaction; Quadrant III (Low priority), representing low interest and low satisfaction; and Quadrant IV (Possible overkill), representing high interest and low satisfaction relative to the grand means (A, B). GI, glycemic index.

Fig. 4.

Mean interest and satisfaction scores for nutrition education delivery methods by age group. (A) Interest and (B) satisfaction were rated on a 5-point Likert scale (1 = not at all, 5 = very much). PPT, PowerPoint presentation; Video, multimedia video-based instruction; Experiential, hands-on experiential learning; Game, gamified educational activities; Mean, composite mean score.

Table 1.

Content and delivery strategies of a behavioral intervention program for individuals with T2DM based on the HBM

Session	Major theme	Subtheme	Factor	Content	Instructional materials
1	The three principles of healthy eating	Weight control methods	Perceived severity	- To delineate the current sex-specific prevalence of obesity in the Republic of Korea	- PowerPoint presentation
			Perceived severity	- To identify and elucidate the major determinants contributing to the development of obesity-related chronic diseases	- Handout (including BMI, waist circumference calculation sheet)
			Perceived benefits	- To recognize that maintaining an optimal (standard) body weight is associated with reduced risks of diabetes-related complications and other chronic diseases	- PowerPoint presentation
			Perceived benefits	- To acknowledge that achieving a healthy body weight enables improved self-efficacy and supports a confident, health-promoting lifestyle	- PowerPoint presentation
			Cues to action	- Calculation of BMI	- PowerPoint presentation
				- Calculation of IBW
				- Estimation of daily energy requirements
		The three principles of healthy eating (balance, regularity, and appropriateness)	Perceived severity	- To assess the status of nutritional imbalance and the incidence of chronic diseases	- PowerPoint presentation
			Perceived severity	- To understand the increased risk of diabetic complications	- A spin wheel-based evaluation tool to assess dietary habits
			Perceived benefits	- To understand the metabolic regulation, prevention of constipation, and risk reduction of chronic diseases through adequate nutrient intake	- PowerPoint presentation
				- To recognize the role of balanced dietary practices in maintaining overall nutritional health
				- To learn the prevention of hypoglycemia through regular meal consumption
				- To understand obesity prevention through appropriate dietary intake
			Self-efficacy	- To develop balanced meal plans using the food exchange system	- PowerPoint presentation
			Self-efficacy	- To understand the concept of the food composition wheel for dietary planning and meal structuring	- Food models to understand appropriate individual portion sizes
		Distinguishing between low and high GI foods	Perceived severity	- To recognize factors that disrupt normal blood glucose levels	- PowerPoint presentation
			Perceived severity	- To understand the increased risk of hyperglycemia	- PowerPoint presentation
			Perceived benefits	- To recognize strategies that reduce the risk of hyperglycemia	- A video clip on the GI
			Self-efficacy	- To distinguish between foods with high and low GI using GI values	- Assessment tool to differentiate between high and low GI foods
			Self-efficacy	- To understand how cooking methods affect GI	- Nutrition cards to summarize GI information
2	Reduced sugar and sodium intake	Guidelines for appropriate sugar consumption	Perceived severity	- To investigate the consumption patterns of sweet and salty foods among older adults in Korea and their association with age-related increases in diabetes and hypertension prevalence	- PowerPoint presentation
			Perceived severity		- A taste assessment tool to evaluate sweet and salty taste perception
			Perceived benefits	- To recognize the maintenance of normal blood glucose levels	- PowerPoint presentation
				- To recognize the reduction in the occurrence of diabetes-related complications
				- To understand preventive measures for hyperglycemia
				- To understand preventive measures for obesity and dental caries
			Self-efficacy	- To understand the recommended daily intake of sugars	- PowerPoint presentation
			Self-efficacy	- To understand evidence-based strategies for appropriate sugar consumption, including interpreting nutrition labels, making informed food choices and preparations, and selecting beverages wisely	- A video clip on sugar intake
		Recommended strategies for appropriate sodium consumption	Perceived severity	- To recognize the increased risk of hypertension associated with excessive sodium intake	- PowerPoint presentation
			Perceived benefits	- To recognize the maintenance of normal blood pressure	- PowerPoint presentation
				- To recognize preventive measures for hypertension
				- To understand risk reduction for cardiovascular disease, gastritis, gastric cancer, and osteoporosis
			Self-efficacy	- To provide guidance on the equivalent amount of seasoning corresponding to 1 g of salt	- PowerPoint presentation
			Self-efficacy	- To understand proper sodium consumption methods and strategies to support sodium excretion (potassium intake, magnesium intake, calcium intake) during cooking, food purchasing, and eating out	- A video clip on sodium intake

T2DM, type 2 diabetes mellitus; HBM, health belief model; BMI, body mass index [body weight (kg)/height² (m²)]; IBW, ideal body weight; GI, glycemic index.

Table 2.

Development of nutrition education cards and videos

Themes	Content	Cards	Videos
GI animation	Definition of GI
	Blood glucose response to high-GI foods
	Blood glucose response to low-GI foods
	Examples of high-GI foods
	Examples of low-GI foods
	Recommended daily intake 80:20 rule¹⁾
Exchange system	Definition of the food exchange system
	Interchangeable portions
	Recommendations for variety in food exchanges
Beverage selection	Sugar content in carbonated and vitamin-fortified beverages
	Nutrition facts of carbonated and vitamin-fortified beverages
	Composition of freshly squeezed fruit juices
	Sugar content in fruit juices
	Nutrition labels of commercially available fruit juices
	Sugar content in mixed coffee (prepackaged coffee)
	Comparison of sugar content: mixed coffee vs. Americano
Sodium reduction	Self-assessment test for habitual high-sodium intake
Sodium reduction	Strategies for reducing sodium intake: product selection, nutrition labels, cooking methods, low-sodium cooking, dietary habits

GI, glycemic index.

¹⁾80:20 rule: A guideline balancing 80% health-focused food choices with 20% flexible dietary enjoyment.

Table 3.

Sociodemographic characteristics of study participants (n = 21)

Classification	Value
Sex
Male	15 (71.4)
Female	6 (28.6)
Age (year)
36–44	4 (19.0)
45–54	2 (9.5)
55–64	9 (42.9)
65–74	6 (28.6)
Education level
Less than high school	7 (33.3)
High school graduate	6 (28.6)
Currently enrolled in university	1 (4.8)
University graduate	5 (23.8)
Currently enrolled in graduate school	0 (0.0)
Graduate school graduate or higher	2 (9.5)
Household composition
Alone	4 (19.0)
Spouse	13 (61.9)
Children	11 (52.3)
Friends/acquaintances	1 (4.8)
Others	1 (4.8)
Smoking
Yes	4 (19.0)
No	17 (81.0)
Alcohol intake
Yes	11 (52.4)
No	10 (47.6)
Frequency of blood glucose monitoring
≥ 4 times/day	0 (0.0)
2–3 times/day	3 (14.3)
1 time/day	9 (42.9)
≥ 3 times/week	2 (9.5)
1–2 times/week	3 (14.3)
Others	4 (19.0)
Total	21 (100.0)

n (%).

Household composition was assessed using multiple responses.

Table 4.

Effects of the behavioral intervention program on nutrition knowledge by age group

Variables	Adults (n = 15)					Older adults (n = 6)
Variables	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)
Goals of dietary therapy for diabetes	0.07 ± 0.26	0.20 ± 0.41	0.13 ± 0.35	0.157	0.38	0.17 ± 0.41	0.33 ± 0.52	0.17 ± 0.75	0.564	0.49
Foods that raise blood glucose the most	0.80 ± 0.41	0.73 ± 0.46	–0.07 ± 0.59	0.655	0.16	1.00 ± 0.00	0.83 ± 0.41	–0.17 ± 0.41	0.317	0.59
Foods that raise blood glucose the least	0.47 ± 0.52	0.87 ± 0.35	0.40 ± 0.63	0.034	0.90	0.17 ± 0.41	0.67 ± 0.52	0.50 ± 0.55	0.083	1.07
Foods that patients with diabetes can consume freely	0.47 ± 0.52	0.67 ± 0.49	0.20 ± 0.86	0.366	0.40	0.50 ± 0.55	0.33 ± 0.52	–0.17 ± 0.75	0.564	0.32
Foods that cannot be consumed relatively freely	0.47 ± 0.51	0.60 ± 0.51	0.13 ± 0.41	0.083	0.39	0.50 ± 0.55	0.33 ± 0.52	–0.17 ± 0.75	0.564	0.32
Foods with equivalent nutritional value to meat	0.73 ± 0.46	0.80 ± 0.41	0.07 ± 0.46	0.564	0.16	0.83 ± 0.41	1.00 ± 0.00	0.17 ± 0.41	0.317	0.59
Foods highest in fat content	0.27 ± 0.46	0.27 ± 0.46	0.00 ± 0.66	> 0.999	0.00	0.17 ± 0.41	0.17 ± 0.41	0.00 ± 0.00	> 0.999	0.00
Foods highest in carbohydrate content	0.53 ± 0.52	0.67 ± 0.49	0.13 ± 0.35	0.157	0.28	0.50 ± 0.55	0.50 ± 0.55	0.00 ± 0.00	> 0.999	0.00
Basic principles of dietary therapy for diabetes	0.87 ± 0.35	0.93 ± 0.26	0.07 ± 0.46	0.564	0.19	1.00 ± 0.00	0.50 ± 0.55	–0.50 ± 0.55	0.083	1.29
Dietary therapy for prevention of diabetic complications	0.60 ± 0.51	0.80 ± 0.41	0.20 ± 0.78	0.180	0.43	0.50 ± 0.55	0.67 ± 0.52	0.17 ± 0.75	0.564	0.32
Foods that can replace 140 g of cooked rice	0.40 ± 0.51	0.60 ± 0.51	0.20 ± 0.78	0.317	0.39	0.33 ± 0.52	0.67 ± 0.52	0.33 ± 0.82	0.317	0.65
Amounts of fruits or vegetables equivalent to 1 exchange unit of apple	0.07 ± 0.26	0.07 ± 0.26	0.00 ± 0.38	> 0.999	0.00	0.17 ± 0.41	0.00 ± 0.00	–0.17 ± 0.41	0.317	0.58
Foods that can replace 200 mL of whole milk	0.40 ± 0.51	0.33 ± 0.49	–0.07 ± 0.59	0.655	0.14	0.33 ± 0.52	0.67 ± 0.52	0.33 ± 0.52	0.157	0.65
Appropriate snack intake	0.80 ± 0.42	0.80 ± 0.41	0.00 ± 0.54	> 0.999	0.00	0.50 ± 0.55	0.83 ± 0.41	0.33 ± 0.52	0.157	0.68
Treatment and management of hypoglycemia	0.67 ± 0.49	0.67 ± 0.49	0.00 ± 0.54	> 0.999	0.00	0.33 ± 0.52	0.67 ± 0.52	0.33 ± 0.82	0.317	0.65
Total	0.50 ± 0.16	0.60 ± 0.14	0.10 ± 0.17	0.042	0.67	0.47 ± 0.16	0.54 ± 0.21	0.08 ± 0.18	0.257	0.37

Mean ± SD.

Nutrition knowledge was assessed using 15 multiple-choice questions, with 1 point awarded for each correct answer; higher scores indicated greater nutrition knowledge.

Each item was scored as correct (1) or incorrect, including “don’t know” responses (0). The mean score for each item represents the proportion of correct responses, and the total score represents the mean proportion of correct responses across the 15 items. Higher scores indicate greater nutrition knowledge.

P-values were calculated using the Wilcoxon signed-rank test.

Table 5.

Effects of the behavioral intervention program on dietary behaviors by age group

Variable	Adults (n = 15)					Older adults (n = 6)
Variable	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)
Avoiding snacks at each meal and consuming appropriate meal portions	2.80 ± 0.86	2.60 ± 0.63	–0.20 ± 0.86	0.366	0.27	2.67 ± 1.21	3.17 ± 0.75	0.50 ± 1.38	0.414	0.50
Eating three regular meals daily at 4–5 hour intervals	2.67 ± 1.05	2.67 ± 0.90	0.00 ± 0.93	> 0.999	0.00	3.33 ± 1.03	3.17 ± 0.98	–0.17 ± 0.98	0.655	0.16
Considering food exchanges during meals	1.73 ± 0.70	1.93 ± 0.96	0.20 ± 1.01	0.453	0.24	1.83 ± 1.17	2.17 ± 0.75	0.33 ± 1.21	0.480	0.35
Reducing intake of sugars during meals	2.60 ± 0.74	2.67 ± 0.62	0.07 ± 0.59	0.655	0.10	2.67 ± 1.37	3.00 ± 0.89	0.33 ± 1.21	0.480	0.29
Consuming appropriate amounts of grain-based foods	2.53 ± 0.64	2.67 ± 0.49	0.13 ± 0.52	0.317	0.25	2.83 ± 1.17	3.17 ± 0.98	0.33 ± 1.03	0.414	0.32
Reducing intake of snacks other than healthy options	2.40 ± 0.74	2.60 ± 0.63	0.20 ± 0.86	0.408	0.29	2.83 ± 1.17	2.83 ± 1.17	0.00 ± 0.89	> 0.999	0.00
Consuming meat, fish, and other protein-rich side dishes at each meal	1.87 ± 0.35	2.07 ± 0.59	0.20 ± 0.68	0.257	0.41	2.50 ± 0.84	2.50 ± 1.05	0.00 ± 0.63	> 0.999	0.00
Consuming sufficient vegetable side dishes at each meal	2.33 ± 0.82	2.33 ± 0.72	0.00 ± 1.00	> 0.999	0.00	2.83 ± 0.98	2.00 ± 0.63	–0.83 ± 0.98	0.102	1.01
Limiting fat intake at each meal	2.13 ± 0.64	2.20 ± 0.56	0.07 ± 0.70	0.705	0.12	2.83 ± 0.98	2.00 ± 0.63	–0.83 ± 0.75	0.059	1.01
Limiting high-calorie and oily foods when eating out and eating balanced meals	2.07 ± 0.80	2.40 ± 0.51	0.33 ± 0.98	0.190	0.49	2.33 ± 1.37	2.67 ± 1.03	0.33 ± 0.52	0.157	0.28
Checking nutrition labels when selecting foods	1.73 ± 0.70	2.27 ± 0.88	0.53 ± 0.83	0.033	0.68	2.00 ± 1.55	2.00 ± 1.55	0.00 ± 0.00	> 0.999	0.00
Abstaining from alcohol or consuming in moderation	2.27 ± 1.28	3.20 ± 0.94	0.93 ± 1.62	0.072	0.83	3.00 ± 1.27	1.83 ± 1.33	–1.17 ± 2.56	0.281	0.90
Total	2.26 ± 0.42	2.47 ± 0.28	0.21 ± 0.34	0.038	0.59	2.64 ± 0.89	2.54 ± 0.66	–0.10 ± 0.67	0.916	0.13

Mean ± SD.

Dietary behaviors were assessed using 12 items rated on a 4-point Likert scale (1 = strongly disagree, 4 = strongly agree); higher scores indicated more favorable dietary behaviors.

P-values were calculated using the Wilcoxon signed-rank test.

Table 6.

Effects of the behavioral intervention program on dietary attitudes by age group

Variable	Adults (n = 15)					Older adults (n = 6)
Variable	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)
Consuming meals in appropriate amounts at regular times is important for blood glucose control	3.53 ± 0.52	3.67 ± 0.49	0.13 ± 0.52	0.317	0.28	3.33 ± 0.52	3.33 ± 0.52	0.00 ± 0.00	> 0.999	0.00
Timing meals and snacks according to insulin action is important	3.27 ± 0.46	3.33 ± 0.62	0.07 ± 0.59	0.655	0.11	3.00 ± 0.63	3.17 ± 0.41	0.17 ± 0.41	0.317	0.32
Using nutrition labels for dietary management is essential	3.13 ± 0.35	3.40 ± 0.51	0.27 ± 0.46	0.046	0.62	2.50 ± 0.84	3.33 ± 0.52	0.83 ± 1.17	0.102	1.19
Monitoring and limiting intake of simple sugars (candy, sugar, honey) is important	3.27 ± 0.46	3.47 ± 0.64	0.20 ± 0.56	0.180	0.36	3.00 ± 0.63	3.00 ± 1.10	0.00 ± 1.27	> 0.999	0.00
Being cautious of foods high in sodium (salt, soy sauce, processed foods) is important	3.27 ± 0.46	3.60 ± 0.51	0.33 ± 0.62	0.059	0.68	2.83 ± 0.75	3.17 ± 0.75	0.33 ± 1.03	0.414	0.40
Being cautious of foods high in fat and cholesterol is important	3.27 ± 0.46	3.47 ± 0.52	0.20 ± 0.56	0.180	0.41	3.00 ± 0.63	3.33 ± 0.52	0.33 ± 1.03	0.414	0.57
Proper adherence to diabetes dietary therapy leads to effective blood glucose control	3.47 ± 0.64	3.53 ± 0.52	0.07 ± 0.80	0.739	0.10	3.33 ± 0.52	3.67 ± 0.52	0.33 ± 0.82	0.317	0.65
Diabetes dietary therapy is not difficult to follow	3.07 ± 0.46	3.07 ± 0.70	0.00 ± 0.54	> 0.999	0.00	3.33 ± 0.52	3.33 ± 0.52	0.00 ± 0.00	> 0.999	0.00
Consuming a balanced diet considering meal composition is important	3.33 ± 0.52	3.40 ± 0.63	0.07 ± 0.70	0.705	0.12	3.17 ± 0.75	3.50 ± 0.55	0.33 ± 0.82	0.317	0.50
Weight management is important for blood glucose control	3.47 ± 0.52	3.53 ± 0.52	0.07 ± 0.46	0.564	0.12	3.17 ± 0.75	3.17 ± 0.41	0.00 ± 0.63	> 0.999	0.00
Reducing intake of unhealthy snacks is important	3.40 ± 0.51	3.47 ± 0.52	0.07 ± 0.59	0.655	0.14	3.50 ± 0.55	3.33 ± 0.52	–0.17 ± 0.41	0.317	0.32
Consuming alcohol in appropriate amounts or abstaining is important for blood glucose control	3.20 ± 0.56	3.53 ± 0.52	0.33 ± 0.62	0.059	0.72	3.50 ± 0.55	2.67 ± 1.03	–0.83 ± 0.98	0.102	1.01
Total	3.31 ± 0.34	3.46 ± 0.41	0.15 ± 0.39	0.195	0.40	3.14 ± 0.33	3.25 ± 0.47	0.11 ± 0.39	0.673	0.27

Mean ± SD.

Dietary attitudes were assessed using 12 items rated on a 4-point Likert scale (1 = strongly disagree, 4 = strongly agree); higher scores indicated more favorable dietary attitudes.

P-values were calculated using the Wilcoxon signed-rank test.

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Development of a nutrition program for Koreans with type 2 diabetes based on the health belief model: a pre-post intervention study

Korean J Community Nutr. 2026;31(4):309-327. Published online August 31, 2026

DOI: https://doi.org/10.5720/kjcn.2026.00234

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Development of a nutrition program for Koreans with type 2 diabetes based on the health belief model: a pre-post intervention study

Fig. 1. Development and evaluation process for the behavioral intervention program.

Fig. 2. Participant recruitment and intervention flow for the behavioral intervention program.

Fig. 3. Interest–satisfaction analysis matrices for nutrition education attributes by content and delivery method. Each point represents the mean perceived interest score (x-axis) and satisfaction score (y-axis), measured on a 5-point Likert scale ranging from 1 (not at all interested/satisfied) to 5 (very interested/satisfied). The horizontal and vertical reference lines indicate the grand mean scores. (A) In the content-based analysis, the quadrants were defined using a grand mean interest score of 4.44 and a grand mean satisfaction score of 4.43. (B) In the delivery method analysis, the quadrants were defined using grand mean scores of 4.45 for both interest and satisfaction. The matrices were divided into four strategic quadrants: Quadrant I (Keep it up), representing high interest and high satisfaction; Quadrant II (Concentrate here), representing low interest and high satisfaction; Quadrant III (Low priority), representing low interest and low satisfaction; and Quadrant IV (Possible overkill), representing high interest and low satisfaction relative to the grand means (A, B). GI, glycemic index.

Fig. 4. Mean interest and satisfaction scores for nutrition education delivery methods by age group. (A) Interest and (B) satisfaction were rated on a 5-point Likert scale (1 = not at all, 5 = very much). PPT, PowerPoint presentation; Video, multimedia video-based instruction; Experiential, hands-on experiential learning; Game, gamified educational activities; Mean, composite mean score.

Fig. 1.

Fig. 2.

Fig. 3.

Fig. 4.

Development of a nutrition program for Koreans with type 2 diabetes based on the health belief model: a pre-post intervention study

Session	Major theme	Subtheme	Factor	Content	Instructional materials
1	The three principles of healthy eating	Weight control methods	Perceived severity	- To delineate the current sex-specific prevalence of obesity in the Republic of Korea	- PowerPoint presentation
			Perceived severity	- To identify and elucidate the major determinants contributing to the development of obesity-related chronic diseases	- Handout (including BMI, waist circumference calculation sheet)
			Perceived benefits	- To recognize that maintaining an optimal (standard) body weight is associated with reduced risks of diabetes-related complications and other chronic diseases	- PowerPoint presentation
			Perceived benefits	- To acknowledge that achieving a healthy body weight enables improved self-efficacy and supports a confident, health-promoting lifestyle	- PowerPoint presentation
			Cues to action	- Calculation of BMI	- PowerPoint presentation
				- Calculation of IBW
				- Estimation of daily energy requirements
		The three principles of healthy eating (balance, regularity, and appropriateness)	Perceived severity	- To assess the status of nutritional imbalance and the incidence of chronic diseases	- PowerPoint presentation
			Perceived severity	- To understand the increased risk of diabetic complications	- A spin wheel-based evaluation tool to assess dietary habits
			Perceived benefits	- To understand the metabolic regulation, prevention of constipation, and risk reduction of chronic diseases through adequate nutrient intake	- PowerPoint presentation
				- To recognize the role of balanced dietary practices in maintaining overall nutritional health
				- To learn the prevention of hypoglycemia through regular meal consumption
				- To understand obesity prevention through appropriate dietary intake
			Self-efficacy	- To develop balanced meal plans using the food exchange system	- PowerPoint presentation
			Self-efficacy	- To understand the concept of the food composition wheel for dietary planning and meal structuring	- Food models to understand appropriate individual portion sizes
		Distinguishing between low and high GI foods	Perceived severity	- To recognize factors that disrupt normal blood glucose levels	- PowerPoint presentation
			Perceived severity	- To understand the increased risk of hyperglycemia	- PowerPoint presentation
			Perceived benefits	- To recognize strategies that reduce the risk of hyperglycemia	- A video clip on the GI
			Self-efficacy	- To distinguish between foods with high and low GI using GI values	- Assessment tool to differentiate between high and low GI foods
			Self-efficacy	- To understand how cooking methods affect GI	- Nutrition cards to summarize GI information
2	Reduced sugar and sodium intake	Guidelines for appropriate sugar consumption	Perceived severity	- To investigate the consumption patterns of sweet and salty foods among older adults in Korea and their association with age-related increases in diabetes and hypertension prevalence	- PowerPoint presentation
			Perceived severity		- A taste assessment tool to evaluate sweet and salty taste perception
			Perceived benefits	- To recognize the maintenance of normal blood glucose levels	- PowerPoint presentation
				- To recognize the reduction in the occurrence of diabetes-related complications
				- To understand preventive measures for hyperglycemia
				- To understand preventive measures for obesity and dental caries
			Self-efficacy	- To understand the recommended daily intake of sugars	- PowerPoint presentation
			Self-efficacy	- To understand evidence-based strategies for appropriate sugar consumption, including interpreting nutrition labels, making informed food choices and preparations, and selecting beverages wisely	- A video clip on sugar intake
		Recommended strategies for appropriate sodium consumption	Perceived severity	- To recognize the increased risk of hypertension associated with excessive sodium intake	- PowerPoint presentation
			Perceived benefits	- To recognize the maintenance of normal blood pressure	- PowerPoint presentation
				- To recognize preventive measures for hypertension
				- To understand risk reduction for cardiovascular disease, gastritis, gastric cancer, and osteoporosis
			Self-efficacy	- To provide guidance on the equivalent amount of seasoning corresponding to 1 g of salt	- PowerPoint presentation
			Self-efficacy	- To understand proper sodium consumption methods and strategies to support sodium excretion (potassium intake, magnesium intake, calcium intake) during cooking, food purchasing, and eating out	- A video clip on sodium intake

Themes	Content	Cards	Videos
GI animation	Definition of GI
	Blood glucose response to high-GI foods
	Blood glucose response to low-GI foods
	Examples of high-GI foods
	Examples of low-GI foods
	Recommended daily intake 80:20 rule¹⁾
Exchange system	Definition of the food exchange system
	Interchangeable portions
	Recommendations for variety in food exchanges
Beverage selection	Sugar content in carbonated and vitamin-fortified beverages
	Nutrition facts of carbonated and vitamin-fortified beverages
	Composition of freshly squeezed fruit juices
	Sugar content in fruit juices
	Nutrition labels of commercially available fruit juices
	Sugar content in mixed coffee (prepackaged coffee)
	Comparison of sugar content: mixed coffee vs. Americano
Sodium reduction	Self-assessment test for habitual high-sodium intake
Sodium reduction	Strategies for reducing sodium intake: product selection, nutrition labels, cooking methods, low-sodium cooking, dietary habits

Classification	Value
Sex
Male	15 (71.4)
Female	6 (28.6)
Age (year)
36–44	4 (19.0)
45–54	2 (9.5)
55–64	9 (42.9)
65–74	6 (28.6)
Education level
Less than high school	7 (33.3)
High school graduate	6 (28.6)
Currently enrolled in university	1 (4.8)
University graduate	5 (23.8)
Currently enrolled in graduate school	0 (0.0)
Graduate school graduate or higher	2 (9.5)
Household composition
Alone	4 (19.0)
Spouse	13 (61.9)
Children	11 (52.3)
Friends/acquaintances	1 (4.8)
Others	1 (4.8)
Smoking
Yes	4 (19.0)
No	17 (81.0)
Alcohol intake
Yes	11 (52.4)
No	10 (47.6)
Frequency of blood glucose monitoring
≥ 4 times/day	0 (0.0)
2–3 times/day	3 (14.3)
1 time/day	9 (42.9)
≥ 3 times/week	2 (9.5)
1–2 times/week	3 (14.3)
Others	4 (19.0)
Total	21 (100.0)

Variables	Adults (n = 15)					Older adults (n = 6)
Variables	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)
Goals of dietary therapy for diabetes	0.07 ± 0.26	0.20 ± 0.41	0.13 ± 0.35	0.157	0.38	0.17 ± 0.41	0.33 ± 0.52	0.17 ± 0.75	0.564	0.49
Foods that raise blood glucose the most	0.80 ± 0.41	0.73 ± 0.46	–0.07 ± 0.59	0.655	0.16	1.00 ± 0.00	0.83 ± 0.41	–0.17 ± 0.41	0.317	0.59
Foods that raise blood glucose the least	0.47 ± 0.52	0.87 ± 0.35	0.40 ± 0.63	0.034	0.90	0.17 ± 0.41	0.67 ± 0.52	0.50 ± 0.55	0.083	1.07
Foods that patients with diabetes can consume freely	0.47 ± 0.52	0.67 ± 0.49	0.20 ± 0.86	0.366	0.40	0.50 ± 0.55	0.33 ± 0.52	–0.17 ± 0.75	0.564	0.32
Foods that cannot be consumed relatively freely	0.47 ± 0.51	0.60 ± 0.51	0.13 ± 0.41	0.083	0.39	0.50 ± 0.55	0.33 ± 0.52	–0.17 ± 0.75	0.564	0.32
Foods with equivalent nutritional value to meat	0.73 ± 0.46	0.80 ± 0.41	0.07 ± 0.46	0.564	0.16	0.83 ± 0.41	1.00 ± 0.00	0.17 ± 0.41	0.317	0.59
Foods highest in fat content	0.27 ± 0.46	0.27 ± 0.46	0.00 ± 0.66	> 0.999	0.00	0.17 ± 0.41	0.17 ± 0.41	0.00 ± 0.00	> 0.999	0.00
Foods highest in carbohydrate content	0.53 ± 0.52	0.67 ± 0.49	0.13 ± 0.35	0.157	0.28	0.50 ± 0.55	0.50 ± 0.55	0.00 ± 0.00	> 0.999	0.00
Basic principles of dietary therapy for diabetes	0.87 ± 0.35	0.93 ± 0.26	0.07 ± 0.46	0.564	0.19	1.00 ± 0.00	0.50 ± 0.55	–0.50 ± 0.55	0.083	1.29
Dietary therapy for prevention of diabetic complications	0.60 ± 0.51	0.80 ± 0.41	0.20 ± 0.78	0.180	0.43	0.50 ± 0.55	0.67 ± 0.52	0.17 ± 0.75	0.564	0.32
Foods that can replace 140 g of cooked rice	0.40 ± 0.51	0.60 ± 0.51	0.20 ± 0.78	0.317	0.39	0.33 ± 0.52	0.67 ± 0.52	0.33 ± 0.82	0.317	0.65
Amounts of fruits or vegetables equivalent to 1 exchange unit of apple	0.07 ± 0.26	0.07 ± 0.26	0.00 ± 0.38	> 0.999	0.00	0.17 ± 0.41	0.00 ± 0.00	–0.17 ± 0.41	0.317	0.58
Foods that can replace 200 mL of whole milk	0.40 ± 0.51	0.33 ± 0.49	–0.07 ± 0.59	0.655	0.14	0.33 ± 0.52	0.67 ± 0.52	0.33 ± 0.52	0.157	0.65
Appropriate snack intake	0.80 ± 0.42	0.80 ± 0.41	0.00 ± 0.54	> 0.999	0.00	0.50 ± 0.55	0.83 ± 0.41	0.33 ± 0.52	0.157	0.68
Treatment and management of hypoglycemia	0.67 ± 0.49	0.67 ± 0.49	0.00 ± 0.54	> 0.999	0.00	0.33 ± 0.52	0.67 ± 0.52	0.33 ± 0.82	0.317	0.65
Total	0.50 ± 0.16	0.60 ± 0.14	0.10 ± 0.17	0.042	0.67	0.47 ± 0.16	0.54 ± 0.21	0.08 ± 0.18	0.257	0.37

Variable	Adults (n = 15)					Older adults (n = 6)
Variable	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)
Avoiding snacks at each meal and consuming appropriate meal portions	2.80 ± 0.86	2.60 ± 0.63	–0.20 ± 0.86	0.366	0.27	2.67 ± 1.21	3.17 ± 0.75	0.50 ± 1.38	0.414	0.50
Eating three regular meals daily at 4–5 hour intervals	2.67 ± 1.05	2.67 ± 0.90	0.00 ± 0.93	> 0.999	0.00	3.33 ± 1.03	3.17 ± 0.98	–0.17 ± 0.98	0.655	0.16
Considering food exchanges during meals	1.73 ± 0.70	1.93 ± 0.96	0.20 ± 1.01	0.453	0.24	1.83 ± 1.17	2.17 ± 0.75	0.33 ± 1.21	0.480	0.35
Reducing intake of sugars during meals	2.60 ± 0.74	2.67 ± 0.62	0.07 ± 0.59	0.655	0.10	2.67 ± 1.37	3.00 ± 0.89	0.33 ± 1.21	0.480	0.29
Consuming appropriate amounts of grain-based foods	2.53 ± 0.64	2.67 ± 0.49	0.13 ± 0.52	0.317	0.25	2.83 ± 1.17	3.17 ± 0.98	0.33 ± 1.03	0.414	0.32
Reducing intake of snacks other than healthy options	2.40 ± 0.74	2.60 ± 0.63	0.20 ± 0.86	0.408	0.29	2.83 ± 1.17	2.83 ± 1.17	0.00 ± 0.89	> 0.999	0.00
Consuming meat, fish, and other protein-rich side dishes at each meal	1.87 ± 0.35	2.07 ± 0.59	0.20 ± 0.68	0.257	0.41	2.50 ± 0.84	2.50 ± 1.05	0.00 ± 0.63	> 0.999	0.00
Consuming sufficient vegetable side dishes at each meal	2.33 ± 0.82	2.33 ± 0.72	0.00 ± 1.00	> 0.999	0.00	2.83 ± 0.98	2.00 ± 0.63	–0.83 ± 0.98	0.102	1.01
Limiting fat intake at each meal	2.13 ± 0.64	2.20 ± 0.56	0.07 ± 0.70	0.705	0.12	2.83 ± 0.98	2.00 ± 0.63	–0.83 ± 0.75	0.059	1.01
Limiting high-calorie and oily foods when eating out and eating balanced meals	2.07 ± 0.80	2.40 ± 0.51	0.33 ± 0.98	0.190	0.49	2.33 ± 1.37	2.67 ± 1.03	0.33 ± 0.52	0.157	0.28
Checking nutrition labels when selecting foods	1.73 ± 0.70	2.27 ± 0.88	0.53 ± 0.83	0.033	0.68	2.00 ± 1.55	2.00 ± 1.55	0.00 ± 0.00	> 0.999	0.00
Abstaining from alcohol or consuming in moderation	2.27 ± 1.28	3.20 ± 0.94	0.93 ± 1.62	0.072	0.83	3.00 ± 1.27	1.83 ± 1.33	–1.17 ± 2.56	0.281	0.90
Total	2.26 ± 0.42	2.47 ± 0.28	0.21 ± 0.34	0.038	0.59	2.64 ± 0.89	2.54 ± 0.66	–0.10 ± 0.67	0.916	0.13

Variable	Adults (n = 15)					Older adults (n = 6)
Variable	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)	Pre	Post	Δ (Post–pre)	P-value	Effect size (Cohen’s d)
Consuming meals in appropriate amounts at regular times is important for blood glucose control	3.53 ± 0.52	3.67 ± 0.49	0.13 ± 0.52	0.317	0.28	3.33 ± 0.52	3.33 ± 0.52	0.00 ± 0.00	> 0.999	0.00
Timing meals and snacks according to insulin action is important	3.27 ± 0.46	3.33 ± 0.62	0.07 ± 0.59	0.655	0.11	3.00 ± 0.63	3.17 ± 0.41	0.17 ± 0.41	0.317	0.32
Using nutrition labels for dietary management is essential	3.13 ± 0.35	3.40 ± 0.51	0.27 ± 0.46	0.046	0.62	2.50 ± 0.84	3.33 ± 0.52	0.83 ± 1.17	0.102	1.19
Monitoring and limiting intake of simple sugars (candy, sugar, honey) is important	3.27 ± 0.46	3.47 ± 0.64	0.20 ± 0.56	0.180	0.36	3.00 ± 0.63	3.00 ± 1.10	0.00 ± 1.27	> 0.999	0.00
Being cautious of foods high in sodium (salt, soy sauce, processed foods) is important	3.27 ± 0.46	3.60 ± 0.51	0.33 ± 0.62	0.059	0.68	2.83 ± 0.75	3.17 ± 0.75	0.33 ± 1.03	0.414	0.40
Being cautious of foods high in fat and cholesterol is important	3.27 ± 0.46	3.47 ± 0.52	0.20 ± 0.56	0.180	0.41	3.00 ± 0.63	3.33 ± 0.52	0.33 ± 1.03	0.414	0.57
Proper adherence to diabetes dietary therapy leads to effective blood glucose control	3.47 ± 0.64	3.53 ± 0.52	0.07 ± 0.80	0.739	0.10	3.33 ± 0.52	3.67 ± 0.52	0.33 ± 0.82	0.317	0.65
Diabetes dietary therapy is not difficult to follow	3.07 ± 0.46	3.07 ± 0.70	0.00 ± 0.54	> 0.999	0.00	3.33 ± 0.52	3.33 ± 0.52	0.00 ± 0.00	> 0.999	0.00
Consuming a balanced diet considering meal composition is important	3.33 ± 0.52	3.40 ± 0.63	0.07 ± 0.70	0.705	0.12	3.17 ± 0.75	3.50 ± 0.55	0.33 ± 0.82	0.317	0.50
Weight management is important for blood glucose control	3.47 ± 0.52	3.53 ± 0.52	0.07 ± 0.46	0.564	0.12	3.17 ± 0.75	3.17 ± 0.41	0.00 ± 0.63	> 0.999	0.00
Reducing intake of unhealthy snacks is important	3.40 ± 0.51	3.47 ± 0.52	0.07 ± 0.59	0.655	0.14	3.50 ± 0.55	3.33 ± 0.52	–0.17 ± 0.41	0.317	0.32
Consuming alcohol in appropriate amounts or abstaining is important for blood glucose control	3.20 ± 0.56	3.53 ± 0.52	0.33 ± 0.62	0.059	0.72	3.50 ± 0.55	2.67 ± 1.03	–0.83 ± 0.98	0.102	1.01
Total	3.31 ± 0.34	3.46 ± 0.41	0.15 ± 0.39	0.195	0.40	3.14 ± 0.33	3.25 ± 0.47	0.11 ± 0.39	0.673	0.27

Table 1. Content and delivery strategies of a behavioral intervention program for individuals with T2DM based on the HBM

T2DM, type 2 diabetes mellitus; HBM, health belief model; BMI, body mass index [body weight (kg)/height² (m²)]; IBW, ideal body weight; GI, glycemic index.

Table 2. Development of nutrition education cards and videos

GI, glycemic index.

80:20 rule: A guideline balancing 80% health-focused food choices with 20% flexible dietary enjoyment.

Table 3. Sociodemographic characteristics of study participants (n = 21)

n (%).

Household composition was assessed using multiple responses.

Table 4. Effects of the behavioral intervention program on nutrition knowledge by age group

Mean ± SD.

Nutrition knowledge was assessed using 15 multiple-choice questions, with 1 point awarded for each correct answer; higher scores indicated greater nutrition knowledge.

P-values were calculated using the Wilcoxon signed-rank test.

Table 5. Effects of the behavioral intervention program on dietary behaviors by age group

Mean ± SD.

Dietary behaviors were assessed using 12 items rated on a 4-point Likert scale (1 = strongly disagree, 4 = strongly agree); higher scores indicated more favorable dietary behaviors.

P-values were calculated using the Wilcoxon signed-rank test.

Table 6. Effects of the behavioral intervention program on dietary attitudes by age group

Mean ± SD.

Dietary attitudes were assessed using 12 items rated on a 4-point Likert scale (1 = strongly disagree, 4 = strongly agree); higher scores indicated more favorable dietary attitudes.