UMIN-ICDS Clinical Trial

Public title

A Study of How Brief Health and Social Media Information Affects Weight Ideals and Body Perceptions in Japanese Adults

Acronym

DHI-WI Trial

Scientific Title

Effects of Digital Information Interventions on Desire for Thinness: A Nationwide Online Randomized Controlled Trial

Scientific Title:Acronym

DHI-WI Trial

Region

Japan

Condition

Desire for thinness and perceptions of healthy body weight among Japanese adults

Classification by specialty

Adult

Classification by malignancy

Others

Genomic information

NO

Narrative objectives1

This study aims to examine the immediate effects of brief digital health information interventions on desire for thinness and health-related cognitions among Japanese adults aged 18-69 years.
Participants were randomly assigned to one of three groups: (A) general health and lifestyle information (control), (B) information on healthy body weight (BMI 22) and physical function, or (C) digital and social media literacy information related to body image.
The primary outcome was the change in the Desire-to-Thinness Index (DTI), calculated from self-reported ideal body weight before and immediately after the intervention. Secondary assessments included body size perception, body satisfaction, and perceptions of healthy body weight.

Basic objectives2

Efficacy

Basic objectives -Others

Trial characteristics_1

Exploratory

Trial characteristics_2

Explanatory

Developmental phase

Not applicable

Primary outcomes

Change in the Desire-to-Thinness Index (DTI) from immediately before to immediately after the intervention.
DTI was calculated using the participant's self-reported ideal body weight and height: DTI = [(22 - ideal BMI) / 22] * 100.
The primary outcome was the pre-to-post intervention change in DTI (immediately post-intervention minus pre-intervention), compared across the three randomized groups.

Key secondary outcomes

1. Change in perceived body size: Self-perceived body size is assessed using a five-point scale immediately before and after the intervention.
2. Change in body satisfaction: Satisfaction with current body size is assessed using a five-point scale immediately before and after the intervention.
3. Perception of healthy body weight: The extent to which a BMI of approximately 22 is considered a useful reference for healthy body weight is assessed using a five-point scale immediately after the intervention.
4. Awareness of future health: Awareness of future health considerations, including muscle, bone, and physical fitness, is assessed using a five-point scale immediately after the intervention.
5. Intention to consider healthy weight beyond body weight alone: The intention to consider muscle, bone, and physical fitness in addition to body weight is assessed using a five-point scale immediately after the intervention.

Study type

Interventional

Basic design

Parallel

Randomization

Randomized

Randomization unit

Individual

Blinding

Open -no one is blinded

Control

Active

Stratification

YES

Dynamic allocation

NO

Institution consideration

Institution is not considered as adjustment factor.

Blocking

Concealment

No. of arms

3

Purpose of intervention

Educational,Counseling,Training

Type of intervention

Other

Interventions/Control_1

Group A: General health information (control group).
Participants are presented with three digital educational slides covering general healthy lifestyle habits, including physical activity, sleep, diet, hydration, and daily routines.
Each slide is displayed for at least 20 seconds, followed by a three-option comprehension question.
The intervention is delivered once in a single online session and takes approximately 1-2 minutes. Ideal body weight and body-related perceptions are assessed before and immediately after the intervention.

Interventions/Control_2

Group B: Healthy body weight and physical function information.
Participants are presented with three digital educational slides explaining BMI 22 as a reference value for standard body weight and emphasizing the importance of considering muscle, bone, physical fitness, and long-term health rather than body weight alone.
Each slide is displayed for at least 20 seconds, followed by a three-option comprehension question.
The intervention is delivered once in a single online session and takes approximately 1-2 minutes. Ideal body weight and body-related perceptions are assessed before and immediately after the intervention.

Interventions/Control_3

Group C: Digital and social media literacy information.
Participants are presented with three digital educational slides explaining how edited images, selective social media posts, recommendation algorithms, repeated exposure to body-related content, and social comparisons may influence body image perceptions.
Each slide is displayed for at least 20 seconds, followed by a three-option comprehension question.
The intervention is delivered once in a single online session and takes approximately 1-2 minutes. Ideal body weight and body-related perceptions are assessed before and immediately after the intervention.

Interventions/Control_4

Interventions/Control_5

Interventions/Control_6

Interventions/Control_7

Interventions/Control_8

Interventions/Control_9

Interventions/Control_10

Age-lower limit

18

years-old

<=

Age-upper limit

69

years-old

>=

Gender

Male and Female

Key inclusion criteria

1. Japanese adults aged 18-69 years.
2. Individuals residing in Japan and holding Japanese nationality.
3. Individuals able to understand and complete a Japanese-language online questionnaire.
4. Individuals meeting the prespecified eligibility criteria during online screening.
5. Individuals who provided informed consent to participate after reviewing the study information online.

Key exclusion criteria

1. Individuals reporting a diagnosis of any prespecified major chronic disease during screening.
2. Individuals currently receiving dietary or physical activity restrictions due to medical conditions.
3. Individuals whose self-reported height or body weight falls outside the prespecified sex-specific eligibility ranges.
4. Individuals without Japanese nationality or unable to complete the questionnaire in Japanese.
5. Individuals who did not provide informed consent.

Target sample size

1200

Name of lead principal investigator

1st name	Tomohiro
Middle name
Last name	Yasuda

Organization

Seirei Christopher University

Division name

School of Nursing

Zip code

433-8558

Address

3453 Mikatabara, Chuo-ku, Hamamatsu, Shizuoka 433-8558, Japan

TEL

053-439-1417

Email

tomohiro-y@seirei.ac.jp

Name of contact person

1st name	Tomohiro
Middle name
Last name	Yasuda

Organization

Seirei Christopher University

Division name

School of Nursing

Zip code

433-8558

Address

3453 Mikatabara, Chuo-ku, Hamamatsu, Shizuoka 433-8558, Japan

TEL

053-439-1417

Homepage URL

Email

tomohiro-y@seirei.ac.jp

Institute

Seirei Christopher University

Institute

Department

Personal name

Tomohiro Yasuda

Organization

Seirei Christopher University

Organization

Division

Category of Funding Organization

Other

Nationality of Funding Organization

Japan

Co-sponsor

Name of secondary funder(s)

Organization

Seirei Christopher University Research Ethics Committee

Address

3453 Mikatabara, Chuo-ku, Hamamatsu, Shizuoka 433-8558, Japan

Tel

053-439-1400

Email

rinri@seirei.ac.jp

Secondary IDs

NO

Study ID_1

Org. issuing International ID_1

Study ID_2

Org. issuing International ID_2

IND to MHLW

Institutions

聖隷クリストファー大学（静岡県）

Date of disclosure of the study information

2026

Year

10

Month

27

Day

URL releasing protocol

Publication of results

Unpublished

URL related to results and publications

Number of participants that the trial has enrolled

1221

Results

Results date posted

Results Delayed

Results Delay Reason

Date of the first journal publication of results

Baseline Characteristics

Participant flow

A total of 1,221 participants were randomized to three groups: 410 to Group A, 403 to Group B, and 408 to Group C.
After randomization, 21 participants discontinued the online survey: 10 in Group A, 3 in Group B, and 8 in Group C.
A total of 1,200 participants completed the intervention and post-intervention assessments, with 400 participants in each group. These participants were included in the complete-case analysis.

Adverse events

Outcome measures

Plan to share IPD

No current plan to share individual participant data.

IPD sharing Plan description

Deidentified participant-level data are managed by the principal investigator in accordance with the ethics-approved research protocol. There is currently no plan to share individual participant data with external researchers.

Recruitment status

No longer recruiting

Date of protocol fixation

2026

Year

07

Month

03

Day

Date of IRB

2026

Year

07

Month

13

Day

Anticipated trial start date

2026

Year

10

Month

20

Day

Last follow-up date

2026

Year

10

Month

22

Day

Date of closure to data entry

2026

Year

10

Month

22

Day

Date trial data considered complete

Date analysis concluded

Other related information

This three-arm randomized controlled trial involved a single-session online information intervention conducted from October 20 to 22, 2026. The trial was retrospectively registered with UMIN-CTR after participant recruitment, intervention delivery, and immediate post-intervention assessments had been completed. The study was approved by the Research Ethics Committee of Seirei Christopher University. The primary outcome, change in the Desire-to-Thinness Index (DTI) from before to immediately after the intervention, was specified in the ethics-approved research protocol before data collection.
At the initial research funding application stage, a sample size of 1,500 participants was considered. Before recruitment, the final sampling plan was established, targeting 1,200 survey completers stratified by sex and age group. A total of 1,221 participants were randomized, 21 discontinued after randomization, and 1,200 completed the survey.

Registered date

2026

Year

10

Month

27

Day

Last modified on

2026

Year

10

Month

27

Day

Link to view the page

Value
https://center6.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000072580