The purpose of this 5-year study is to conduct multimodal real-time assessment of behavioral, psychosocial, and contextual characteristics to uncover lapse phenotypes. The data from this project will ultimately inform future personalized interventions to promote dietary adherence by providing critical data on which lapses to target and how to best target them. Participants (N=150) will receive 12 months of online behavioral obesity treatment followed by a 6-month maintenance period (18 months of study participation total). The primary aim is to establish lapse phenotypes by identifying clusters of factors that differentiate lapse behavior. The secondary aim is to evaluate associations of emerging lapse phenotypes with clinical outcomes (e.g., energy intake and weight loss). The investigators will also explore the variability in lapse phenotypes based on data collected from the primary outcome.

Participants will be recruited on a rolling basis until the target (N=150) is reached. Participants will be recruited via advertisements in local media (e.g. newspapers, radio) and online advertising (e.g., Google AdWords, social media), flyers and advertisements posted in waiting rooms and exam rooms in primary care offices, informational materials made available as part of the health and wellness program for employees in the Lifespan hospital network, and direct mailings.

Interested individuals will be initially screened for eligibility via REDCap (a Lifespan secure website) or via telephone. If a participant appears to be eligible based on their responses to the screening questions, they will receive a follow-up call from the research team to confirm eligibility, describe the study in more detail, and schedule an orientation meeting. If they are not eligible, they will receive a message indicating that they are not eligible for the study and directed to contact the research team if they wish to receive referrals for other weight loss programs. Those who are eligible will be invited to an orientation via the online video chat forum Zoom, where the study will be described, and informed consent obtained. Only after the consent form is signed will any further study procedures be completed. If consent is not given, participant contact information will be immediately removed from the system. After consent is obtained, participants will complete baseline questionnaires via REDCap. Paper surveys will be made available for participants who prefer this option. If a participant elects to use a paper questionnaire, the questionnaire will be sent to the participant's home address. Participants will then complete a 1-week behavioral run-in in which they complete smartphone-based surveys and wear the sensors. This data is for testing only and will not be used in the analysis of primary outcomes. Participants must complete \>70% of EMA surveys and wear both devices \>10 hrs/day to move forward with the remainder of study procedures. Following consent and successful completion of baseline procedures, participants will attend an in-person "kick-off" session to assist them in using the online BOT program. Participants will be given access to an online BOT (described further in the Intervention section) for 12 months, with an additional 6 months of no treatment follow-up (intended to serve as a weight maintenance period).

During this 18-month study period, participants will complete 5 total assessments at baseline, 3, 6, 12, and 18 months. Each assessment consists of a 14-day monitoring period. There will be 2 visits with trained research staff at the beginning and end of the 14-day monitoring. At the first visit, participants will: have their height/weight measured, receive study equipment (e.g., wearable wrist devices), and undergo training in using study equipment. Participants will be instructed to wear the sensor devices, complete repeated smartphone surveys for 14 days, and complete three non-consecutive telephone-based 24-hour dietary recalls with staff. At the end of 14 days, participants will return for their second visit in which they will: have their weight measured, return study equipment, and receive payment. The research staff do not need to be blinded for study visits because all participants are assigned to the same intervention. Participants will be asked to complete the same assessment procedures at baseline (first two weeks of the online BOT), 3, 6, 12, and 18 months (last two weeks of no- treatment weight maintenance period).