Self-guided intervention with digital tools, periodic informational support, and moderated social networking group for peer support.

Change in body mass index is calculated as weight in kg divided by the square of height in meters. BMI is calculated at each weight assessment and change over time is assessed.

Change in health-related quality of life is measured using the Medical Outcomes Study 36-Item Short Form (SF-36) survey. This survey includes 36 items with eight subscales (physical functioning, role limitations due to physical problems, social functioning, bodily pain, general mental health, role limitations due to emotional problems, vitality, and general health perceptions). Responses are coded on a scale of 0 to 100, where 0 is the worst possible health and 100 is the most favorable health score. The coded responses will be summed to yield a Physical Component Summary (PCS) score and a Mental Component Summary (MCS) score. The measure is administered at baseline, 3, 6, and 12 months and change over time is assessed.

Diet Quality id assessed using the Healthy Eating Index (HEI) using data from the National Cancer Institute's Automated Self-Administered 24-hour Recall (ASA-24). The ASA24 measures food intake for 24 hours and calculates the HEI. Scores for the HEI range from 0 to 100. A higher score represents a better outcome. Participants complete a weekday and weekend day recall at baseline, 6, and 12 months and change over time is assessed.

Change in physical activity is measured as a sum of weekly minutes of light and moderate-to-vigorous physical activity at 6 and 12 months compared to baseline, assessed via wrist-worm Fitbit device. Participants are asked to wear the Fitbit device for a one week during each assessment period at baseline, 6, and 12 months. Change in weekly active minutes will be assessed over time.

Physical activity will be assessed using the Paffenbarger Physical Activity Questionnaire (PAQ) which assesses leisure-time activity. The PAQ provides an estimate of minutes per week of moderate-to-vigorous intensity, and calories/week of light (5 kcal/min), medium (7.5 kcal/min), and high (10 kcal/min) intensity activities. PAQ changes have been predictive of weight change. The measure is administered at baseline, 6, and 12 months and change over time is assessed.

Frailty will be assessed among all participants with a Frailty Index (all participants) Five items assess self-reported fatigue (from SF-36), weight loss, morbidities, difficulty with ambulation (PROMIS Global Health), and ability to overcome resistance (from SF-36).181 The number of positive responses for these components is summed to create the FRAIL index (range 0-5). A value > 3 is considered frail, and a value of 2 is considered prefrail. Frailty is measured at baseline, 6, and 12 months and change over time is assessed.

Frailty will be assessed in a subset of participants assessed in person with a modified Fried frailty phenotype. The modified Fried frailty phenotype includes five clinically derived factors: 1) weakness (sitting dominant hand-grip strength using hand-held dynamometer and BMI-specific cut points); 2) slowness (timed 15-foot walk); 3) sarcopenia (relative mass of =1.5 SDs below age-, sex-, race-specific values from NHANES using bioelectrical impedance analysis; 4) exhaustion (vitality subscale of SF-36; and 5) low energy expenditure (<383 kcal/week for males, < 270 kcal/week for females from Paffenbarger Physical Activity Questionnaire). Individuals with 3 factors are classified as frail and those with 2 factors as pre-frail. Frailty is measured at baseline, 6, and 12 months and change over time is assessed.

Peripheral blood will be collected from a subset of participants assessed in-person. Samples will be used to measure expression of T lymphocyte p16. At each assessment, a whole blood sample of 8mL will be drawn and collected into a 8mL ACD tube. From the ACD tube, analysis of p16 expression will be measured using a TaqMan quantitative reverse-transcription polymerase chain reaction (RTPCR) performed by Sapere Bio (Research Triangle Park, NC). The measure is collected at baseline, 6, and 12 months and change over time will be assessed.

Fasting blood samples (after an overnight fast of at least 8 hours) will be collected from a subset of participants assessed in person. At each assessment, a whole blood sample (collected in one 8.5 mL SST tube) will be collected, processed to serum, and analyzed by LabCorp for lipids (total cholesterol, HDL-C, LDL-C and triglycerides), glucose, and insulin levels. The measures are collected at baseline, 6, and 12 months and change over time will be assessed.

Blood pressure will be assessed in a subset of participants assessed in person with a calibrated blood pressure monitor. Cuff size will be determined by arm circumference. After a 5-minute rest period and with both feet flat on floor, three readings will be taken, with 60 seconds between measurements. The measurement is collected at baseline, 6, and 12 months and change in systolic and diastolic blood pressure will be assessed over time.

Waist circumference will be assessed in a subset of participants assessed in person, measured at the midpoint between highest point of iliac crest and lowest point of costal margin using a Gulik tape measure and following a standard protocol. Two measures of waist circumference are taken; if the difference exceeds 0.5 cm, a third measure is taken. The measurement is collected at baseline, 6, and 12 months and change over time will be assessed.

Body composition assessed in a subset of participants with the BodPod (COSMED USA, Inc.). Participants are asked to fast for 8 hours (including caffeine) and to refrain from strenuous exercise for 8 hours prior to these body composition measures. Outcome variable of interest is change in the ratio of lean muscle mass to fat mass. The measurement is collected at baseline, 6, and 12 months and change in the ratio of lean muscle mass to fat mass is assessed over time.

Physical activity will be assessed among the subset of participants completing in-person assessments using ActiGraph accelerometers (GT3X+, Pensacola, FL), which provides an objective assessment to corroborate self-report PA and sedentary activity data. Participants will be instructed to wear the device at all times for a full week; monitoring for at least 600 min/day for at least 5 days in the week (including at least one weekday and one weekend day) is considered adequate for analysis. Data will be aggregated into sedentary, light and MVPA using standard thresholds. Physical activity with accelerometer will be assessed at baseline, 6, and 12 months.

The 10-item Perceived Stress Scale (PSS-10) measures overall perceived stress during the past month. Items are scored on a 5-point Likert scale from 0 (Never) to 4 (Very Often) with total scores ranging from 0 to 40. Items 4, 5, 7 and 8 are reverse scored. Higher scores indicate higher levels of perceived stress. The measure is administered at baseline, 3, 6, and 12 months and change over time is assessed.

The Generalized Anxiety Disorder 7-item scale (GAD-7) is a self-report measure of generalized anxiety symptoms.183 Possible scores range from 0 to 21, with higher scores reflecting greater symptom severity; cut-points of 5, 10, and 15 correspond to mild, moderate, and severe levels of anxiety. The measure is administered at baseline, 3, 6, and 12 months and change over time is assessed.

The patient-reported outcomes measurement information system (PROMIS) Global Health measure be used to measure perceptions of health. The PROMIS measure consists of 10 self-reported global health items, which assess 5 domains: physical function, pain, fatigue, emotional distress, and social health. The response options are presented as 5-point (as well as a single 11-point) rating scales. The results of the questions are used to calculate two summary scores: a Global Physical Health Score and a Global Mental Health score. Higher values indicate better health. The measure is administered at baseline, 3, 6, and 12 months and change over time is assessed.

Change in perceived competence from baseline to 3, 6 and 12 months as measured using the Perceived Competence for Scale. The Scale measures perceived competence for diet (4 items) and physical activity (4 items). Items are rated on a 7-point Likert scale (1 = not at all true, 7 = very true), and include items such as "I feel confident in my ability to maintain a healthy diet." Scores are summed for the items in the subscale (diet and physical activity) and the range for each subscale is 4 - 28. Greater values indicate higher levels of perceived competence for engaging in positive diet and physical activity behaviors. Scores are summed for the items in the subscale (diet and physical activity). Competence is a hypothesized mediator in this study.

Relatedness will be measured with 3 items adapted from the 8-item Relatedness subscale of the Basic Need Satisfaction at Work Scale. Examples include "The program demonstrates caring about me as a person" and are scored on a Likert scale from 1 (strongly disagree) to 7 (strongly agree). Responses are averaged with a range of 1 to 7. Higher scores indicate a higher level of perceived relatedness from the intervention messages. The measure will be administered at 3, 6, and 12 months and change over time will be assessed. Relatedness is a hypothesized mediator in this study.

Items are adapted from the Health Care Climate Questionnaire, which is a measure of how the participant perceives support from a healthcare provider, to measure autonomy support from the program. The scale includes 15 items rated on a scale of 1 (strongly disagree) to 7 (strongly agree) (e.g., "I feel that [the program] has provided me choices and options.") Scores are calculated by averaging the individual item scores (with item 13 reverse-scored). Higher average scores represent a higher level of perceived autonomy support. Autonomy support will be measured at 3, 6, and 12 months. Autonomy Support is a hypothesized mediator in this study.

Change in treatment self-regulation from baseline to 3, 6, and 12 months as measured using the Treatment Self-Regulation Questionnaire (TSRQ). The TSRQ assesses autonomous and controlled motivation for making changes in diet (15 items) and physical activity (15 items). Examples item: "Because I feel that I want to take responsibility for my own health" answered on a scale of 1 (not at all true) to 7 (very true)." Calculating the scores for the sub-scales will consist of averaging the items on that subscale. They are: Autonomous Regulation: 2, 3, 7, 10, 13, 16, 18, 19 Controlled Regulation: 1, 4, 5, 6, 8, 9, 11, 12, 14, 15, 17. Responses to the items within the subscale are averaged with the range of scores being 1 to 7. Higher values on each subscale indicate greater levels of that type of motivation. Autonomous Motivation is a hypothesized mediator in this study.