The purpose of this phase II trial is to identify the most effective dose level (number of classes) of a diet and physical activity lifestyle program based on how well it improves diet and physical activity in stage 0-III breast cancer survivors. Study results may provide researchers with information on how to best implement diet and physical activity recommendations among breast cancer survivors.

OUTLINE: Participants are randomized to 1 of 2 arms.

ARM A (LOW DOSE): Participants attend one diet and physical activity class delivered remotely via Zoom and receive an eHealth communication intervention for 6 months.

ARM B (HIGH DOSE): Participants attend 12 twice monthly diet and physical activity online sessions delivered remotely via Zoom and receive an eHealth communication intervention for 6 months.

Inclusion Criteria:

• Previous diagnosis of stage 0-III breast cancer in the past 10 years at the time of enrollment
• No evidence of recurrent or metastatic disease
• No uncontrolled diabetes mellitus defined as glycosylated hemoglobin (Hgb A1C) > 8%
• No uncontrolled hypertension per Seattle Cancer Care Alliance (SCCA) standard of care
• At least 60 days post final chemotherapy, biologic therapy, or radiation therapy and/or surgery. Current use of endocrine therapy is permitted (e.g., tamoxifen and aromatase inhibitors)
• Access to phone for study contacts
• Access to smartphone, tablet, or computer and internet to attend online session(s) and receive study electronic eHealth communication (text messages and access to website)
• Willing and able to attend the online session(s) on Saturdays, or via online accessed videos, for up to 12 sessions in 6 months
• Successfully complete all run-in activities, including at-home and over the phone assessments, 7 days of collecting physical activity data via accelerometer, and providing blood and stool sample
• Willing and able to complete all study activities for 6 months after randomization
• Participants must consume < 5 servings of fruits and vegetables per day and/or engage in < 150 minutes per week of moderate to vigorous physical activity, as assessed by brief questionnaires
• Participants must have an Eastern Cooperative Oncology Group (ECOG) Scale of performance status score of 0 or 1 for performance status.
• Signed physician approval for diet change and physical activity
• Able to understand and willing to sign written informed electronic (e) consent in English

Exclusion Criteria:

• Participants must not be active smokers within the past 30 days.
• Women must not be pregnant at time of enrollment