Continuous Glucose Monitoring and Dietary Self-Management in Adults in Namwon

This community-based, individually randomized, open-label, wait-list controlled study evaluates the incremental effect of adding a continuous glucose monitoring (CGM) device as a personal glucose biofeedback tool to a common digital health and education program during the first 6 weeks. The randomized comparison is device provision versus no device provision during this period; standardized education and behavioral goal setting are common to both groups. Approximately 3,000 residents are expected to undergo screening to identify 860 eligible participants who provide additional written consent for randomization. Screening participants who do not enter the randomized study are not part of its control group. Their separately consented optional week 12 follow-up will be analyzed descriptively and separately from the randomized comparison. For these nonrandomized participants, the optional follow-up window is Days 77-91 after the first screening visit.

The actual randomization date is Day 0. Randomization is preferably completed at the first screening visit after eligibility verification, required consent, and baseline assessments, but may occur later without a separate maximum screening-to-randomization interval. Before allocation, willingness to participate, treatment, safety status, and sensor-use changes are rechecked. The week 6 assessment window is Days 35-49 and the week 12 window is Days 77-91 after randomization. Sensor placement delays do not reset Day 0. Screening, consent, baseline assessment, randomization, and sensor placement dates are recorded separately. Scheduling must permit completion within the approved study period and the planned field-assessment end in September 2027.

If screening and randomization occur on different dates, the four dietary self-management items are collected again before allocation using the same wording, response options, and recall periods. The mean of the first three items collected before allocation on the randomization date is the primary baseline score. Same-day assessments are not duplicated. Other baseline questionnaires, AI Diet, and physical measurements use the pre-allocation values from the first screening visit, retaining the measurement dates and screening-to-randomization interval. Post-allocation values are not substituted for baseline. The interval is described by group and included in an additional adjusted sensitivity analysis.

Allocation will be 1:1 using a web-based system operated outside the field research team, with computer-generated variable blocks and three strata: documented type 2 diabetes diagnosis or treatment; no documented diagnosis or treatment with fasting glucose at least 126 mg/dL; and no documented diagnosis or treatment with fasting glucose from 100 through 125 mg/dL. The primary analyst will finalize the analysis plan and code using group labels A and B before the group code is revealed. Participants and field researchers will know the assigned timing.

Beginning at the first screening visit, both groups receive the PASTA application, the commercially available AI Diet dietary assessment and feedback provided through Kakao Healthcare's PASTA application, CancerFree prevention information, digital literacy support, and basic health counseling. Both groups also receive the same standardized education on glucose patterns, relationships of meals, activity and sleep with glucose responses, and safe behavioral goal setting during the first 6 weeks, independently of sensor provision. Education and goal setting are not deferred in the control group. The added intervention is access to the CGM device and linked personal glucose feedback. Sensor placement, connection, and device safety instructions are provided when each group actually starts using its sensor.

The primary comparison is the week 6 dietary self-management score, adjusted for its baseline value, diabetes stratum, and initial enrollment location. The study-specific score is based on the mean of the first three dietary self-management items adapted with revised wording and response guidance from the Korean version of the Summary of Diabetes Self-Care Activities. It is not presented as an independently validated instrument. The fourth item, concerning carbohydrate distribution, is reserved for a sensitivity analysis.

After the week 6 outcome assessment and data lock, the wait-list control group is offered the same sensor so that all eligible randomized participants have an opportunity to receive the device. The first 6 weeks constitute the primary controlled intervention period; each sensor is worn for approximately 10 days, not continuously for 6 weeks. Week 12 assessments are exploratory follow-up after both groups have been offered the sensor. The study is not primarily designed to establish superiority of early versus delayed provision. No on-site blood sampling is planned. Optional psychosocial assessments and planned administrative data linkage, conditional on later separate consent and approvals, are exploratory and do not replace the primary randomized comparison.

AI Diet uses the existing 10 dietary categories and their commercially provided risk-stage table without modification. For the prespecified exploratory analysis, the four category-assigned stages for obesity, diabetes, hypertension, and hypertriglyceridemia are summed. Each stage ranges from 1 (lowest) to 4 (highest); the sums across the 10 existing categories range from 4 to 13. A higher sum indicates a higher combined category-assigned risk stage. This sum is not an individual probability of disease. Category transitions are also examined.

With separate consent, PASTA records actually generated during the 24-month study period may be received for exploratory analyses beyond the 12-week field follow-up. The current National Health Insurance Service linkage-plan and follow-up-contact consent does not authorize actual linkage or collection of resident registration numbers. Actual linkage requires a confirmed lawful processing route, responsible entities, approvals, and later separate explanation and consent. Pseudonymized analysis is planned in the approved National Health Insurance Service environment, with only approved analytical outputs released; individual insurance records are not downloaded or stored by the research team. One linkage is planned after all week 12 visits, within the study period ending in September 2028. Up to five years of records before the first screening visit are used to assess prior history. Incident outcomes are observed from the actual randomization date to the actual linkage date for randomized participants, and from the first screening visit for the separately consented nonrandomized follow-up cohort, subject to record availability. The overall study end is not treated as each participant's observed follow-up end.

Protocol version 8 received ethics approval. The version 9 amendment will undergo ethics review before implementation of the amended study plan.

• Continuous Glucose Monitoring With Application-Based Biofeedback (Device): One Dexcom G7 sensor is worn for approximately 10 days, with personal glucose patterns displayed through PASTA as biofeedback for lifestyle self-management. The device group starts on the actual randomization date (Day 0) or within 10 business days. The wait-list control group receives no device during the first 6 weeks and is offered the sensor after the week 6 assessment and data lock, on that day or within 7 business days, to provide access for all eligible participants. Both groups receive the same standardized education and behavioral goal setting during the first 6 weeks. The primary contrast is the incremental device effect during that period. Sensor placement, connection, and safety instructions accompany actual use. Research staff do not adjust medicines based on readings.
• Common Standardized Education and Behavioral Goal Setting (Behavioral): Both randomized groups receive the same standardized education and behavioral goal-setting support during the first 6 weeks, regardless of whether a CGM device has been provided. Education covers interpretation of glucose patterns, relationships of meals, activity and sleep with glucose responses, differences in responses to foods, and safe behavioral goals. Safety guidance includes not changing medicines, insulin or food intake solely on the basis of sensor readings. This is a common component, not the randomized difference; it is not postponed until sensor provision in the wait-list control group. Instructions for actual sensor placement, application connection, and device safety are distinguished from this common education.
• Common Digital Health Program and Basic Health Counseling (Behavioral): Both randomized groups receive the same background program beginning at the first screening visit, which may precede randomization: PASTA application guidance, the commercially available AI Diet dietary assessment and feedback provided through Kakao Healthcare's PASTA application, using the existing 10 dietary categories and risk-stage table without modification, CancerFree prevention information, assistance with digital skills, and basic health counseling. Standardized education and behavioral goal setting are also common to both groups during the first 6 weeks. Personal glucose-linked functions become available only when a sensor is provided; actual placement, connection, and device safety instructions accompany device use. The common background program has no separate untreated comparator in this study.

Primary outcomes

• Dietary Self-Management Score at Week 6 [Week 6 after the actual randomization date (Day 0); assessment window: Days 35-49.]: Study-specific mean of three adapted items: healthy eating, healthy eating plan adherence, and vegetable consumption. Items 1 and 3 recall the past 7 days; item 2 recalls average weekly practice over the past month. Items and mean range 0-7; higher scores indicate more frequent self-management. No reverse scoring. With one missing item, use the mean of two; with two or more missing, the score is missing. Compare week 6 scores with adjustment for the pre-allocation score on the randomization date, diabetes-status stratum, and enrollment location. If screening occurred earlier, repeat all four dietary items before allocation; use the first three for this baseline. This adapted score is not an unchanged validated scale. If ill in the most recent 7 days, use the preceding 7 days without illness for 7-day items.

Secondary outcomes

• Average Weekly PASTA Application Login Days [From the actual randomization date (Day 0) through the week 6 assessment (Days 35-49).]: Mean number of days per week with a login to the PASTA digital health application, from the actual randomization date (Day 0) through the week 6 assessment (range 0-7 days/week; higher values indicate more frequent use). Participants with confirmed non-installation or no use are assigned zero; records unavailable because of data transfer failure or withdrawn data permission are treated as missing. Glucose-linked functions are available only to the device group before week 6, which is considered when interpreting between-group differences.
• Body Weight at Week 6 [Week 6 after the actual randomization date (Day 0); assessment window: Days 35-49.]: Body weight in kilograms, measured at the study visit. The week 6 value is compared between randomized groups with adjustment for baseline body weight, diabetes-status stratum, and enrollment location. Baseline is the pre-allocation measurement from the first screening visit.
• Waist Circumference at Week 6 [Week 6 after the actual randomization date (Day 0); assessment window: Days 35-49.]: Waist circumference in centimeters, measured at the study visit. The week 6 value is compared between randomized groups with adjustment for baseline waist circumference, diabetes-status stratum, and enrollment location. Baseline is the pre-allocation measurement from the first screening visit.
• Systolic Blood Pressure at Week 6 [Week 6 after the actual randomization date (Day 0); assessment window: Days 35-49.]: Systolic blood pressure in millimeters of mercury, measured at the study visit. The week 6 value is compared between randomized groups with adjustment for baseline systolic blood pressure, diabetes-status stratum, and enrollment location. Baseline is the pre-allocation measurement from the first screening visit.
• Diastolic Blood Pressure at Week 6 [Week 6 after the actual randomization date (Day 0); assessment window: Days 35-49.]: Diastolic blood pressure in millimeters of mercury, measured at the study visit. The week 6 value is compared between randomized groups with adjustment for baseline diastolic blood pressure, diabetes-status stratum, and enrollment location. Baseline is the pre-allocation measurement from the first screening visit.

Other outcomes

• Dietary Self-Management Score at Week 12 [Week 12 after the actual randomization date (Day 0); assessment window: Days 77-91.]: Mean of the same first three study-specific dietary self-care items used for the primary outcome, ranging from 0 to 7, with higher scores indicating more frequent dietary self-management. If one item is missing, the mean of the two available items is used; if two or more are missing, the score is missing. Exploratory follow-up after both groups have been offered a sensor. Results are described by original randomized group and do not represent a concurrent device-versus-no-device comparison; the primary controlled comparison ends at week 6.
• Body Weight at Week 12 [Week 12 after the actual randomization date (Day 0); assessment window: Days 77-91.]: Body weight in kilograms at the week 12 visit. Exploratory follow-up after both groups have been offered a sensor. Results are described by original randomized group and do not represent a concurrent device-versus-no-device comparison; the primary controlled comparison ends at week 6.
• Waist Circumference at Week 12 [Week 12 after the actual randomization date (Day 0); assessment window: Days 77-91.]: Waist circumference in centimeters at the week 12 visit. Exploratory follow-up after both groups have been offered a sensor. Results are described by original randomized group and do not represent a concurrent device-versus-no-device comparison; the primary controlled comparison ends at week 6.
• Systolic Blood Pressure at Week 12 [Week 12 after the actual randomization date (Day 0); assessment window: Days 77-91.]: Systolic blood pressure in millimeters of mercury at the week 12 visit. Exploratory follow-up after both groups have been offered a sensor. Results are described by original randomized group and do not represent a concurrent device-versus-no-device comparison; the primary controlled comparison ends at week 6.
• Diastolic Blood Pressure at Week 12 [Week 12 after the actual randomization date (Day 0); assessment window: Days 77-91.]: Diastolic blood pressure in millimeters of mercury at the week 12 visit. Exploratory follow-up after both groups have been offered a sensor. Results are described by original randomized group and do not represent a concurrent device-versus-no-device comparison; the primary controlled comparison ends at week 6.
• Participants With Adverse Events [From the first screening visit through the week 12 assessment (Days 77-91 after randomization).]: Number of participants reporting adverse events during visits or technical support contacts, including skin reactions, dizziness, anxiety, and emergency medical care. Events are recorded with severity, relationship to the intervention, actions taken, and outcome. Device problems and privacy incidents are also recorded as safety-related events.
• Change in AI Diet Dietary Pattern Category [Baseline at the first screening visit to week 6 (Days 35-49 after randomization).]: Proportion of participants whose dietary pattern category assigned by the commercially available AI Diet service in Kakao Healthcare's PASTA application, using the existing 10 dietary categories without modification, differs between baseline and week 6. The full category-to-category transition distribution is also described. This is an exploratory measure of change in categorical assignment and does not imply a change in risk level within an unchanged category.
• New Diabetes Diagnosis in Linked Health Insurance Records [From the actual randomization date (Day 0) to a single linkage after all week 12 visits, within the study period ending September 2028.]: Exploratory occurrence of a new diabetes diagnosis in National Health Insurance Service records among participants with later separate linkage consent and available records, after the processing route and required approvals are established. Current linkage-plan and follow-up-contact consent alone does not authorize data linkage. Up to five years before the first screening visit assess prior history. Incident events are assessed from randomization (Day 0) to the actual single linkage date after all week 12 visits. Results are described by randomized group with actual observation periods, record availability, and missing data. These optional selected data do not replace the primary randomized comparison.
• New Initiation of Glucose-Lowering Medication or Insulin in Linked Health Insurance Records [From the actual randomization date (Day 0) to a single linkage after all week 12 visits, within the study period ending September 2028.]: Exploratory occurrence of newly initiated glucose-lowering medication or insulin in National Health Insurance Service records among participants with later separate linkage consent and available records, after the processing route and required approvals are established. Current linkage-plan and follow-up-contact consent alone does not authorize data linkage. Up to five years before the first screening visit assess prior history. Incident events are assessed from randomization (Day 0) to the actual single linkage date after all week 12 visits. Results are described by randomized group with actual observation periods, record availability, and missing data. These optional selected data do not replace the primary randomized comparison.
• AI Diet Metabolic Dietary Risk Score at Week 6 [Week 6 after the actual randomization date (Day 0); assessment window: Days 35-49.]: Exploratory score derived from the commercially available AI Diet service in Kakao Healthcare's PASTA application. The existing 10 dietary categories and their risk-stage table are used without modification. For each category, the provided stages for obesity, diabetes, hypertension, and hypertriglyceridemia are each coded 1 (lowest) to 4 (highest) and summed for analysis. The attainable total across the existing categories ranges from 4 to 13; higher totals indicate higher combined category-assigned risk stages. The week 6 score is compared between randomized groups with adjustment for the pre-allocation baseline score from the first screening visit, diabetes-status stratum, and initial enrollment location. This sum is not an individual probability of disease and cannot reflect within-category changes when the assigned category remains unchanged.

Sex: All, ages: 40 Years to any

Inclusion Criteria:

* Resident of Namwon, Republic of Korea, aged 40 years or older.
* Able to understand the study, express a choice, and provide voluntary written informed consent.
* Able to participate in questionnaires, health-record review, dietary assessment, counseling, and basic measurements, with research-team assistance for smartphone or application use when needed.
* At least one of the following glycemic-risk criteria: documented type 2 diabetes diagnosis or treatment with glucose-lowering medication or insulin; no documented diagnosis or treatment with the most recent fasting glucose at least 126 mg/dL; or no documented diagnosis or treatment with the most recent fasting glucose from 100 through 125 mg/dL.
* Eligibility is verified at the first screening visit. Randomization preferably occurs that day but may occur later, without a separate maximum interval, after required consent and pre-allocation assessments. Before allocation, willingness to participate, treatment, safety status, and sensor-use changes are rechecked. The actual randomization date is Day 0. If it differs from screening, the four dietary self-management items are repeated before allocation; other baseline measures remain those from the first screening visit. Participants without a qualifying fasting glucose result or objective type 2 diabetes diagnosis or treatment documentation at that visit are not randomized. For fasting-glucose-based eligibility, the result must be from within two years before the first screening visit. The most recent available national health-screening result is used, unless a more recent medical-facility result explicitly identified as fasting glucose is provided. Existing diagnosis or treatment must be supported by objective documentation such as a prescription record, medication package or medication itself, or a medical certificate; self-report alone is insufficient. Documented type 2 diabetes diagnosis or treatment permits eligibility without an available fasting glucose result. Relevant partial copies or on-site review of application screens or paper records may be used; submission of the whole health-record file is not required.
* Provides additional written consent for continuous glucose monitoring (CGM), application linkage, data collection, and week 6 and week 12 assessments.
* Provides the separate consents required for transfer of PASTA personal and health data and provision of consent-confirmation information to Kakao Healthcare.
* Investigator judges that CGM can be used safely and follow-up procedures can be completed with assistance when needed.

Exclusion Criteria:

* Unable to understand study-related information or express a choice, or unable to provide valid consent.
* Acute illness, severe symptoms, or another condition that makes study procedures unsafe in the investigator's judgment.
* Severe skin disease at the sensor site, severe adhesive allergy, or a history of serious contact dermatitis.
* Recent acute cardiovascular event, severe infection, active anticancer treatment, or another condition making participation clinically inappropriate.
* Pregnancy or a need for a separate pregnancy-related glucose-management pathway.
* Severe anxiety about sensor readings or concern that CGM use could compromise safe medication or dietary management.
* Any previous or current CGM sensor use, regardless of product, purpose, or duration, or planned non-study CGM use before the week 6 assessment. Clinically necessary CGM use will not be stopped for study participation.
* Type 1 diabetes. Insulin treatment alone does not establish type 1 diabetes.
* Previous participation in the Namwon public health center employee pilot program. Receiving information or making a reservation alone does not constitute prior participation.

Welfare-center participants who have not used a sensor may enter the main study within the 860-participant target only after approval of the amendment, new informed consent, and confirmation of all eligibility criteria. Previously collected welfare-center data are handled only within the scope permitted by ethics review; public health center pilot data are excluded from the main study analysis.

• Ji-Yeob Choi, PhD, Principal investigator, Seoul National University College of Medicine