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NCT Number: NCT07175701

Ultra-processed Food-reducing Intervention and Continuous Glucose Monitoring

The goal of this trial is to investigate whether reduction in ultra-processed food intake through dietary counseling and education can improve postprandial glucose responses and glycemic variability compared with a usual diet in young, healthy Korean adults aged 20-30 years. The main questions it aims to answer are:

- Does reducing ultra-processed food intake, while maintaining total energy intake and usual lifestyle behaviors, improve postprandial glucose and lower glycemic variability in healthy adults without diabetes?

Participants will:

* Undergo the 10-day pre-intervention monitoring period, during which each participant will wear a continuous glucose monitoring (CGM) device and concurrently report their daily dietary intakes (all food and beverage consumption) and other lifestyle behaviors (sleep, smoking, physical activity) * After the 10-day pre-intervention monitoring period, participants will be randomized to either intervention or control group * Intervention group: Participants will visit the research site to receive dietitian-led one-on-one nutrition education and personalized dietary counseling targeting reduction of ultra-processed food intake. Personalized diet counseling will be provided by study dietitian based on participant's records of dietary intakes during the 10-day pre-intervention monitoring period. * Control group: Participants will receive dietitian-led nutrition education and personalized dietary counseling based on the national dietary guidelines. * After the intervention, participants will undergo the 10-day post-intervention monitoring period, during which participants will wear a new CGM device for an additional 10 days and continue daily reporting of dietary intakes (all food and beverage consumptions) and lifestyle behaviors (sleep, smoking, physical activity).

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Key information

Conditions

Postprandial Glucose Glucose Intolerance Glucose Levels Glucose Metabolism Disorders Hyperglycemia Hyperglycemias Metabolic Diseases Nutritional and Metabolic Diseases

Age range

20 year–39 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Health Promotion Lab, College of Health Science, Korea University

Seoul, 02841, South Korea

Location status: Recruiting

Location contact

Hannah Oh, ScD

PRINCIPAL_INVESTIGATOR

Yujin Kim, BSN

CONTACT

[email protected]

+82-10-8712-9763

About this study

The Ultra-Processed Food Reduction Intervention and Continuous Glucose Monitoring (ULTRA-CGM) trial is a parallel, two-arm randomized controlled trial designed to evaluate the effects of a ultra-processed food (UPF)-reducing dietary intervention on postprandial glucose responses and glycemic variability in young Korean adults (aged 20-39 years) using CGM devices. Participants will be randomly assigned to either a UPF-reducing intervention group or a control group maintaining their usual diet. We hypothesize that receiving the UPF-reducing dietary intervention will improve postprandial glucose responses and reduce glycemic variability compared with participants receiving standard dietary counseling based on national guidelines. The findings from this trial may provide experimental evidence on the metabolic effects of reducing UPF consumption and inform dietary strategies for diabetes prevention among younger adults.

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Korean adults aged 20-39 years
  • Not currently pregnant
  • No personal history of diabetes or other glucose-related conditions
  • Consume ≥25% of daily energy intake from UPFs, as assessed by an online, self-administered semi-quantitative screening food frequency questionnaire (FFQ)
  • No restriction on wearing a CGM device
  • No increased risk of bleeding
  • No prior adverse reaction to CGM devices
  • Willingness to participate in follow-up assessments

Exclusion criteria

  • Unable to maintain continuous follow-up during the study period (e.g., due to special plans such as traveling)
  • Planning to follow a special or restrictive diet (e.g., for weight loss) during the study period

Treatment and study plan

40-minute one-on-one dietary counseling and nutrition education aimed at reducing ultra-processed food consumption

Behavioral

Participants assigned to the intervention group receive a 40-minute one-on-one nutrition education session and personalized dietary counseling delivered by the study dietitian. The goals of these sessions are to reduce UPF consumption while maintaining total energy intake and usual lifestyle behaviors. All sessions follow a standardized protocol to ensure consistent delivery of the intervention. The study dietitian delivering the intervention receives training on the standardized protocol prior to participant enrollment.

Standard dietary counseling and nutrition education based on national guidelines

Behavioral

Participants assigned to the control group are also provided with a 40-minute one-on-one nutrition education session and personalized dietary counseling, but with different objectives. During these sessions, the national dietary guidelines are introduced using an educational leaflet distributed by the Ministry of Health and Welfare. The education session and counseling provided to the control group do not include any information on UPFs. After completion of the study, participants in the control group are provided with the same nutrition education materials on UPF reduction that are used in the intervention group.

Primary outcomes

  1. Change in postprandial glucose responses

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    The primary outcome of this study is the change in postprandial glucose responses from the baseline monitoring period to the post-intervention monitoring period. Postprandial glucose responses are assessed using CGM and quantified as the incremental area under the curve (iAUC) over 2 hours following each meal. Higher iAUC values indicate greater postprandial glucose excursions.

    For each meal, iAUC is calculated as the area under the curve above the baseline level over the 2-hour postprandial period, using the trapezoidal rule. The baseline glucose level is defined as the mean glucose value in the 5 minutes immediately preceding meal consumption. For overlapping meals, the iAUC for the first meal is calculated from its start until 2 hours after, and overlapping periods are excluded from subsequent meals' iAUC to ensure each glucose excursion is counted once.

Secondary outcomes

  1. Change in coefficient of variation (CV)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    CV indicates relative glycemic variability and is calculated as the standard deviation of glucose measurements assessed using CGM divided by the mean glucose level.

  2. Change in standard deviation (mg/dL)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Standard deviation represents the absolute magnitude of glycemic variability, reflecting the dispersion of glucose values over time, assessed using CGM.

  3. Change in mean amplitude of glycemic excursions (MAGE)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Mean amplitude of glycemic excursions represents the mean amplitude of major glucose excursions. It is calculate by mean height of glycemic excursions (peaks and nadirs) that exceed one SD of the mean glucose over a 24-hour period.

  4. Change in glucose spike frequency

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Glucose spike frequency quantifies the number of distinct glucose excursions above 140 mg/dL, providing an additional measure of postprandial hyperglycemia.

  5. Change in time-in-range (%)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Time-in-range represents the percentage of time spent within the consensus target glucose range of 70-180 mg/dL, as defined by international continuous glucose monitoring consensus recommendations.

  6. Change in time-in-tight-range (%)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Time-in-tight-range represents the percentage of time spent within the tighter target range of 70-140 mg/dL. Because participants are healthy young adults, time-in-tight-range 70-140 mg/dL is considered.

  7. Change in time-above-range (%)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Time-above-range represents the percentage of time spent with glucose levels above 180 mg/dL or 140 mg/dL. Because participants are healthy young adults, time-above-range 140 mg/dL is considered.

  8. Change in time-below-range (%)

    Time frame: Change in mean values from the baseline monitoring period (10-day period before the intervention) to the post-intervention monitoring period (10-day period immediately following the intervention)

    Time-below-range represents the percentage of time spent with glucose levels below 70 mg/dL

  9. Change in body weight (kg)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Body weight will be directly measured by study staff to assess overall adiposity.

  10. Change in waist circumference (cm)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Waist circumference will be directly measured by study staff to assess central adiposity.

  11. Change in fat mass (kg)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Fat mass will be measured using a bioelectrical impedance analyzer (BIA) (InBody 270S; InBody Co., Ltd, Seoul, Korea).

  12. Change in muscle mass (kg)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Muscle mass will be measured using a bioelectrical impedance analyzer (BIA) (InBody 270S; InBody Co., Ltd, Seoul, Korea).

  13. Change in percentage of body fat (%)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Percentage of body fat will be measured using a bioelectrical impedance analyzer (BIA) (InBody 270S; InBody Co., Ltd, Seoul, Korea).

  14. Change in blood pressure measurements (mmHg)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Blood pressures measurements, including both systolic and diastolic values, are measured to capture potential cardiometabolic effects of the intervention. Blood pressure is measured by a trained study nurse (a registered nurse) on the upper arm using an automated blood pressure monitoring device (WatchBP office Target BP3MD1-4; Microlife AG, Switzerland) while participants are seated and at rest. The mean of three consecutive measurements is used for analysis.

  15. Change in handgrip strength (kg)

    Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)

    Handgrip strength is assessed as a marker of muscular strength and functional status. Handgrip strength is assessed using a handgrip dynamometer (T.K.K.-5401; Takei Scientific Instruments Co., Ltd, Tokyo, Japan). Handgrip measurements are performed twice for each hand in an alternating manner, and the highest value is used for analysis

Study contacts

Contact information is provided by the study sponsor or research team.

Yujin Kim, BSN

CONTACT

[email protected]

+82-10-8712-9763

Sponsors and collaborators

Lead sponsor

Korea University

Other

Collaborators

  • Korean Society of Cardiometabolic Syndrome (funder)

Registry information

Official study title

Effects of Ultra-processed Food Reduction Intervention on Postprandial Glucose and Glycemic Variability in Korean Young Adults: Study Protocol for the ULTRA-CGM Randomized Controlled Trial

Acronym: ULTRA-CGM

Important dates

Study start
2025
Primary completion
2026
Study completion
2026
First posted
Sep 16, 2025
Registry last updated
Apr 17, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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