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.
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
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
255
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.
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).
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.
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).
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).
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).
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).
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).
University of North Carolina at Chapel Hill
Chapel Hill, North Carolina, United States
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.
Time frame: 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.
Time frame: 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.
Time frame: Daily throughout the study, a total of up to 24 weeks
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.
Time frame: 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
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: 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.
Time frame: Daily throughout the study, a total of up to 24 weeks
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