Just-in-time Adaptive Intervention Messaging in a Digital Weight Loss Intervention for Young Adults (Nudge)

A Micro-randomized Trial of JITAI Messaging to Improve Adherence to Multiple Weight Loss Behaviors in Young Adults

The purpose of this micro-randomized trial is to evaluate the effects of 7 types of intervention messages targeting specific behavior change techniques (i.e., BCT messages) delivered in "just-in-time" (JIT) moments on daily achievement of weight-related behavioral goals among n=201 young adults with overweight and obesity, participating in a digital, mobile comprehensive lifestyle intervention. "Just-in-time adaptive interventions" (JITAIs) are an alternative to the "one size fits all" approach of mobile intervention development that can provide tailored, real-time messaging and support for young adults.

Study Overview

• Status: Completed
• Conditions: Obesity; Overweight; Overweight and Obesity
• Intervention / Treatment: Behavioral: Core Behavioral Weight Loss (BWL) Intervention; Behavioral: Behavior Change Technique 1 Message (Action Planning); Behavioral: Behavior Change Technique 2 Message (Discrepancy between Current Behavior and Goal); Behavioral: Behavior Change Technique 3 Message (Feedback on Outcome of Behavior); Behavioral: Behavior Change Technique 4 Message (Social Support); Behavioral: Behavior Change Technique 5 Message (Social Comparison); Behavioral: Behavior Change Technique 6 Message (Social Reward); Behavioral: Behavior Change Technique 7 Message (Focus on Past Success)

Detailed Description

An estimated 1 in 2 US adults will have obesity by 2030, which is a major cause of morbidity and mortality. The highest risk of weight gain is among young adults ages 18-35 years. In-person behavioral interventions generally produce clinically significant weight losses, but cost and reduced reach limit their ability to impact obesity at a population level. Web-based interventions that mimic the structure of weekly face-to-face treatment have proven a viable alternative, though weight losses are generally smaller than in-person treatment. Mobile treatments have the potential for high reach, but have been less effective, producing 1-3 kgs over 6 months. Newer digital intervention approaches called "just-in-time adaptive interventions" (JITAIs) promise to improve upon mobile outcomes by offering adaptive, personalized feedback on behavior, which consists of providing the "right type of support" at "the right time" rather than on a fixed schedule. This "just-in- time," or JIT, approach is made possible by the emergence of low-cost and widely available digital health tools that allow for the collection of continually updated health data. However, to date, no JITAIs have successfully targeted multiple weight-related behaviors (weighing, activity, and diet), and there has been no systematic examination of what types of messaging interventions best promote adherence to these three weight loss behaviors, for whom they are effective, and under what conditions. To address this problem, a micro-randomized trial will be used to evaluate the effects of 7 types of intervention messages targeting specific behavior change techniques (i.e., BCT messages) delivered in JIT moments on daily achievement of behavioral goals among n=201 young adults with overweight and obesity. All participants will receive a 6-month behavioral weight loss intervention using our Nudge mobile app, which includes evidence-based weekly lessons, tailored feedback, self-monitoring, and daily BCT messages. Participants will receive a wireless scale, activity tracker, and track "red" foods (high-calorie foods) in the app and have 3 goals: weigh daily, a daily active minutes goal that gradually increases if met, and a daily red foods limit. At 3 decision points per day, participants will be micro-randomized to receive or not receive 1 of 7 types of BCT messages. Each intervention message has unique decision rules for availability. Candidate intervention message options have been carefully selected from empirical evidence, tested in our prior studies, or are from our pilot micro-randomized trial. Assessments will occur daily, and at 0, 3 and 6 months, to accomplish the following specific aims: 1) Evaluate the effects of each behavior change technique message (i.e., BCT message) on daily adherence to weight loss behaviors; 2) Determine whether the effects of BCT messages on proximal outcomes change over time; and 3) Assess whether the effects of BCT messages on proximal outcomes are moderated by participants' contextual factors. Findings will guide how adaptive, behaviorally- and contextually-dependent messages are incorporated into future JITAIs for weight loss.

• Study Type: Interventional
• Enrollment (Actual): 255
• Phase: Not Applicable

Contacts and Locations

Study Locations

• United States
  • North Carolina
    • Chapel Hill, North Carolina, United States, 27514
      • University of North Carolina at Chapel Hill

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years to 35 years (Adult)
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Body mass index (BMI) of 25 - 45 kg/m^2 at baseline
• English-speaking, reading, and writing
• Own a smartphone with a data and text messaging plan

Exclusion Criteria:

• Type 1 diabetes or currently receiving medical treatment for Type 2 diabetes
• Report a heart condition, chest pain during periods of activity or rest, or loss of consciousness on the Physical Activity Readiness Questionnaire (PAR-Q; items 1-4).
• Other health problems which may influence the ability to walk for physical activity or be associated with unintentional weight change, including cancer treatment within the past 5 years or tuberculosis
• Lost 10 lbs. or more of body weight (and kept it off) in the last 6 months
• Past diagnosis of or receiving treatment for a clinically diagnosed eating disorder (anorexia nervosa or bulimia nervosa)
• Current symptoms of alcohol or substance dependence
• Currently pregnant, pregnant within the past 6 months, or planning to become pregnant within the next 6 months
• Untreated thyroid disease or any changes (type or dose) in thyroid medication in last 6 months
• Hospitalization for depression or other psychiatric disorder within the past 12 months
• History of psychotic disorder or bipolar disorder
• Currently participating in a weight loss, nutrition, or physical activity study or program or other study that would interfere with this study
• Currently using prescription medications with known effects on appetite or weight (e.g., oral steroids, weight loss medications), with the exception of individuals on a stable dose of Selective Serotonin Reuptake Inhibitors (SSRIs) for 3 months)
• Previous surgical procedure for weight loss or planned weight loss surgery in the next year
• Another member of the household is a participant or staff member on this trial
• Reason to suspect that the participant would not adhere to the study intervention
• Reside outside of the United States
• Have participated in another study conducted by the UNC Weight Research Program within the past 12 months

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Sequential Assignment
• Masking: Double

Number of Arms

8

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Core Behavioral Weight Loss (BWL) Intervention; Behavioral weight loss core intervention, includes activity tracker, wireless scale, daily self-weighing, and smartphone app with weekly behavioral lessons, food tracking log, weekly tailored feedback summary, and daily weight-related behavioral goals. Core intervention component is combined with each of the 7 intervention messages to be tested repeatedly over time.	Behavioral: Core Behavioral Weight Loss (BWL) Intervention; All participants receive a mobile behavioral weight loss intervention delivered through a study smartphone app with weekly behavioral lessons, food tracking log, weekly tailored feedback, and daily weight-related behavioral goals; a connected physical activity tracker and wireless scale. As micro-randomized trials are sequential, full factorial experiments, this core intervention component is combined with each of the 7 intervention messages (i.e., Behavior Change Technique (BCT) messages) to be tested repeatedly over time. Participants will be evaluated at each of 3 decision points (morning, midday, evening) on each day of the study, and if eligible then micro-randomized, to receive or not receive, 1 of 7 types of daily intervention messages promoting achievement of proximal weight-related behavioral goals.
Experimental: Core BWL Intervention + BCT 1 Message (Action Planning); Core BWL Intervention + Message testing the Behavior Change Technique "Action Planning"	Behavioral: Behavior Change Technique 1 Message (Action Planning); Core BWL Intervention + Message in smartphone app prompts detailed planning of performance of one of the 3 target behaviors (daily weighing, active minutes, red food intake).
Experimental: Core BWL Intervention + BCT 2 Message (Discrepancy); Core BWL Intervention + Message testing the Behavior Change Technique "Discrepancy Between Current Behavior and Goal"	Behavioral: Behavior Change Technique 2 Message (Discrepancy between Current Behavior and Goal); Core BWL Intervention + Message in smartphone app provides feedback on each of the 3 target behaviors (daily weighing, active minutes, red food intake) in the form of information drawing attention to discrepancies between participants' current behavior and participants' daily goals.
Experimental: Core BWL Intervention + BCT 3 Message (Feedback on Outcome of Behavior); Core BWL Intervention + Message testing the Behavior Change Technique "Feedback on Outcome of Behavior"	Behavioral: Behavior Change Technique 3 Message (Feedback on Outcome of Behavior); Core BWL Intervention + Message in smartphone app provides participants with feedback on their weight change, relating it to their performance on one of the 3 target behaviors (daily weighing, active minutes, red food intake).
Experimental: Core BWL Intervention + BCT 4 Message (Social Support); Core BWL Intervention + Message testing the Behavior Change Technique "Social Support"	Behavioral: Behavior Change Technique 4 Message (Social Support); Core BWL Intervention + Message in smartphone app advises participants on eliciting the provision of social support from their existing network related to one of the 3 target behaviors (daily weighing, active minutes, red food intake).
Experimental: Core BWL Intervention + BCT 5 Message (Social Comparison); Core BWL Intervention + Message testing the Behavior Change Technique "Social Comparison"	Behavioral: Behavior Change Technique 5 Message (Social Comparison); Core BWL Intervention + Message in smartphone app systematically induces comparison of participants' behavioral performance with other participants, including general, upward (i.e., comparison to participants doing better: weighing more, engaging in more activity, staying within red food limits), and downward comparisons (to participants doing worse).
Experimental: Core BWL Intervention + BCT 6 Message (Social Reward); Core BWL Intervention + Message testing the Behavior Change Technique "Social Reward"	Behavioral: Behavior Change Technique 6 Message (Social Reward); Core BWL Intervention + Message in smartphone app reinforces participants' effort or progress in performing one of the 3 target behaviors (daily weighing, active minutes, red food intake).
Experimental: Core BWL Intervention + BCT 7 Message (Focus on Past Success); Core BWL Intervention + Message testing the Behavior Change Technique "Focus on Past Success"	Behavioral: Behavior Change Technique 7 Message (Focus on Past Success); Core BWL Intervention + Message in smartphone app advises participants to think about or list previous successes related to performing one of the 3 target behaviors (daily weighing, active minutes, red food intake).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Met Daily Weighing Goal	Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. Among the randomization observations in which the participant had not yet weighed, this outcome is the number of observations in which the daily weighing goal was met after receiving or not receiving a message and before the end of the day. Observations are accumulated across participants and across time. On the day of randomization, a dichotomous outcome of whether a participant weighed or did not weigh is calculated.	Daily throughout the study, a total of up to 24 weeks
Met Daily Active Minutes Goal	Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. Among the randomization observations in which the participant had not yet met their active minutes goal, this outcome is the number of observations in which the daily active minutes goal was met after receiving or not receiving a message and before the end of the day. Observations are accumulated across participants and across time. On the day of randomization, a dichotomous outcome of whether a participant met or did not meet their active minutes goal is calculated.	Daily throughout the study, a total of up to 24 weeks
At or Under Daily Red Foods Limit	Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. Among the randomization observations in which the participant had not yet exceeded their red foods limit, this outcome is the number of observations in which the participant stayed at or under their daily red foods limit after receiving or not receiving a message and before the end of the day. Observations are accumulated across participants and across time. On the day of randomization, a dichotomous outcome of whether a participant stayed at or under their red foods limit or did not is calculated.	Daily throughout the study, a total of up to 24 weeks

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Weight Change	Absolute weight change (kg) from baseline to 6 months (6-month weight - baseline weight). Weight was objectively measured on a digital scale in the participant's home.	Baseline, 6 months
Percent Weight Change	Change in weight (%) from baseline to 6 months. Weight will be objectively measured on a digital scale in the participant's home. Percent weight change at 6 months is calculated as ((weight (kg) at 6 months - weight (kg) at baseline)/(weight (kg) at baseline))*100	Baseline, 6 months
Proportion of Days Met Daily Weighing Goal	Calculation of the proportion of study days weighed across all study participants across all days.	Daily throughout the study, a total of up to 24 weeks
Proportion of Daily Active Minutes Goal Met	Among randomization observations, the mean proportion of the daily active minutes goal that was achieved that day. Observations are accumulated across participants and across time. Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. On the day of randomization, a ratio of the participant's total active minutes that day over their daily active minutes goal is calculated (total active minutes that day/daily active minutes goal), such that observations in which a participant exceeded their goal have a proportion over 1.0 and those in which a participant did not reach their active minutes goal have a proportion under 1.0.	Daily throughout the study, a total of up to 24 weeks
Proportion of Daily Red Foods Limit	Among randomization observations, the mean proportion of the daily red foods limit that was tracked that day. Observations are accumulated across participants and across time. Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. On the day of randomization, a ratio (proportion) of the participant's total red foods that day over their daily red foods limit is calculated (total red foods that day/daily red foods limit), such that observations in which a participant exceeded their limit have a proportion over 1.0 and those in which a participant did not exceed their red foods limit have a proportion under 1.0.	Daily throughout the study, a total of up to 24 weeks
Number of Active Minutes	Among randomization observations, the total number of active minutes that was achieved by the participant on the day of randomization. Observations are accumulated across participants and across time. Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit.	Daily throughout the study, a total of up to 24 weeks
Number of Red Foods	Among randomization observations, the total number of red foods that was tracked by the participant on the day of randomization. Observations are accumulated across participants and across time. Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit.	Daily throughout the study, a total of up to 24 weeks
Met Daily Weighing Goal Tomorrow	Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. Among the randomization observations, this outcome is the number of observations in which the daily weighing goal was met the day following randomization. Observations are accumulated across participants and across time. On the day following randomization, a dichotomous outcome of whether a participant weighed or did not weigh is assessed.	Daily throughout the study, a total of up to 24 weeks
Met Daily Active Minutes Goal Tomorrow	Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. Among the randomization observations, this outcome is the number of observations in which the daily active minutes goal was met the day following randomization. Observations are accumulated across participants and across time. On the day following randomization, a dichotomous outcome of whether a participant met or did not meet their active minutes goal is calculated.	Daily throughout the study, a total of up to 24 weeks
At or Under Daily Red Foods Limit Tomorrow	Each observation corresponds to a microrandomization decision point; the reported value reflects the outcome measured within that unit. Among the randomization observations, this outcome is the number of observations in which the participant stayed at or under the daily red foods limit the day following randomization. Observations are accumulated across participants and across time. On the day following randomization, a dichotomous outcome of whether a participant stayed at or under the daily red foods limit is calculated.	Daily throughout the study, a total of up to 24 weeks

Collaborators and Investigators

• Sponsor: University of North Carolina, Chapel Hill
• Collaborators: National Heart, Lung, and Blood Institute (NHLBI)
• Investigators: Principal Investigator: Carmina G. Valle, PhD, MPH, Assistant Professor

Study record dates

Study Major Dates

• Study Start (Actual): August 25, 2023
• Primary Completion (Actual): January 5, 2025
• Study Completion (Actual): January 27, 2025

Study Registration Dates

• First Submitted: November 14, 2022
• First Submitted That Met QC Criteria: November 14, 2022
• First Posted (Actual): November 22, 2022

Study Record Updates

• Last Update Posted (Actual): February 17, 2026
• Last Update Submitted That Met QC Criteria: January 29, 2026
• Last Verified: January 1, 2025

More Information

Terms related to this study

• Keywords: Physical Activity; Diet; Behavioral weight loss; Mobile intervention
• Additional Relevant MeSH Terms: Nutrition Disorders; Overnutrition; Body Weight; Pathological Conditions, Signs and Symptoms; Behavior; Nutritional and Metabolic Diseases; Signs and Symptoms; Overweight; Obesity; Motor Activity; Investigative Techniques; Methods
• Other Study ID Numbers: 22-0170; 1R01HL161373 (U.S. NIH Grant/Contract)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: Deidentified individual data that supports the results will be shared beginning 12 to 36 months following publication provided the investigator who proposes to use the data has submitted a written proposal to the Principal Investigator describing the intended use of the data and approval from an Institutional Review Board (IRB), Independent Ethics Committee (IEC), or Research Ethics Board (REB), as applicable, and executes a data use/sharing agreement with UNC. The release of specific data may be delayed if data are part of an analysis being prepared for a separate publication.
• IPD Sharing Time Frame: beginning at 12 and continuing for 36 months following publication
• IPD Sharing Access Criteria: Investigator has UNC PI-approved proposal, institutional IRB, IEC, or REB approval and an executed data use/sharing agreement with UNC
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP; ICF

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No