The purpose of this research study is to learn how to best provide weekly feedback on individual progress toward intervention goals during a weight loss program.

The goal of this micro-randomized factorial trial is to learn how to best deliver self-monitoring feedback during a behavioral weight management intervention. All study participants will be provided with a "Weight Loss 101" session that provides weight loss education and behavioral skills training. At this meeting, participants will be taught how to use study-provided tools to self-monitor their dietary intake, physical activity, and weight. At the end of each week of the intervention, participants will receive an interventionist-composed feedback message based on their self-monitoring data. Every message will contain feedback about how often the participant self-monitored their dietary intake, physical activity, and weight (that is, the number of days each week that the participant monitored each) along with a message about their weight trajectory. Participants will be randomized each week to receive (or not receive) four additional feedback components each week.

The main questions that this study aims to answer are:

• which of the four additional feedback components improve adherence to self-monitoring, intervention goals, and weight loss the week after they are received?
• are there any differences in message impact depending on the person receiving the message (for example, do some messages work better for younger versus older participants) or their context (for example, are certain messages more or less helpful depending on how well the person is doing in the program)?

Inclusion Criteria:

• Age greater than or equal to 18 years
• BMI greater than or equal to 25.0 kg/m2
• Weight less than or equal to 175 kg (due to scale limit)
• Own a smartphone compatible with Fitbit (e.g., an Apple iPhone running iOS 16.4 or higher or Android smartphone running Android 11 or higher) with a cellular and data plan

Exclusion Criteria:

• Weight greater than 175 kg (due to a weight limit of the study-provided scale)
• Smartphone device owned deemed incompatible with the Fitbit App
• History of bariatric surgery or plans to obtain bariatric surgery during the study period
• Current use of weight loss medications, or use of weight loss medications in the 6 months prior to initial pre-screening
• Currently participating in a weight-loss program
• Weight loss of greater than or equal to 10 lbs in the 6 months prior to initial pre-screening
• Physical limitations that prevent walking at a brisk pace for at least 10 minutes without stopping
• Use of a pacemaker or other implanted medical device
• Currently pregnant
• Currently breastfeeding
• Less than 1-year post-partum
• Plans to become pregnant within the study period
• Lack of written confirmation that the potential participant has discussed study participation with their physician if they have been diagnosed with diabetes, hypertension, or has have a history of coronary heart disease
• One or more study participants living in the household (enrollment limited to one participant per household)
• Medical conditions that contraindicate weight loss or prevent completion of the study (e.g., current diagnosis of cancer or terminal illness, dementia, etc.)
• Recent (in the past 6 months) changes in medications that affect weight
• Self-reported eating disorder within past 5 years
• Unable to complete the 17-week study (due to plans to relocate during the study period, etc.)
• Unable or unwilling to provide informed consent
• Unable to read English at the 5th grade level
• Unwilling to accept random assignment
• Unable or unwilling to download the study smartphone application, wear the physical activity monitor, or use the study e-scale
• Failure to complete baseline assessment measures
• Failure to complete at least 4 out of 6 days of self-monitoring dietary and weight self-monitoring during the behavioral run-in period
• Any other condition(s) which, in the opinion of the Principal Investigator, would adversely affect participation in the study

Individual-level participant data will be de-identified and made available: (1) within one year from the final outcome assessment date, (2) at the time of publication of peer-reviewed manuscript(s) based on these data, or (3) at the end of the award, whichever is soonest. Study data will be shared via the Zenodo data repository at https://zenodo.org/. Analytic code will be made publicly available via Supplementary files for any publications and/or via Zenodo through a Zenodo-GitHub link. Study protocol, informed consent form, statistical analysis plan will also be available to be shared via clinicaltrials.gov.

De-identified, individual-level participant data will be made available: (1) within one year from the final outcome assessment date, (2) at the time of publication of peer-reviewed manuscript(s) based on these data, or (3) at the end of the award, whichever is soonest.

Data will be made available via the Zenodo data repository (https://zenodo.org).