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).
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.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
DOUBLE
Enrollment
50
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.
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.
Health Promotion Lab, College of Health Science, Korea University
Seoul, Seoul, South Korea
RECRUITINGChange in postprandial glucose responses
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.
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)
Change in coefficient of variation (CV)
CV indicates relative glycemic variability and is calculated as the standard deviation of glucose measurements assessed using CGM divided by the mean glucose level.
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)
Change in standard deviation (mg/dL)
Standard deviation represents the absolute magnitude of glycemic variability, reflecting the dispersion of glucose values over time, assessed using CGM.
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)
Change in mean amplitude of glycemic excursions (MAGE)
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.
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)
Change in glucose spike frequency
Glucose spike frequency quantifies the number of distinct glucose excursions above 140 mg/dL, providing an additional measure of postprandial hyperglycemia.
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)
Change in time-in-range (%)
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.
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)
Change in time-in-tight-range (%)
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.
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)
Change in time-above-range (%)
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.
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)
Change in time-below-range (%)
Time-below-range represents the percentage of time spent with glucose levels below 70 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)
Change in body weight (kg)
Body weight will be directly measured by study staff to assess overall adiposity.
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
Change in waist circumference (cm)
Waist circumference will be directly measured by study staff to assess central adiposity.
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
Change in fat mass (kg)
Fat mass will be measured using a bioelectrical impedance analyzer (BIA) (InBody 270S; InBody Co., Ltd, Seoul, Korea).
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
Change in muscle mass (kg)
Muscle mass will be measured using a bioelectrical impedance analyzer (BIA) (InBody 270S; InBody Co., Ltd, Seoul, Korea).
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
Change in percentage of body fat (%)
Percentage of body fat will be measured using a bioelectrical impedance analyzer (BIA) (InBody 270S; InBody Co., Ltd, Seoul, Korea).
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
Change in blood pressure measurements (mmHg)
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.
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
Change in handgrip strength (kg)
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
Time frame: Change from study enrollment (day 1) to study completion (day 23; 10 days after the intervention)
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