Using Tailored mHealth Strategies to Promote Weight Management Among Adolescent and Young Adult Cancer Survivors

Inclusion Criteria: * 18-39 years old at the time of consent. * Diagnosed with first invasive cancer between ages 15-39 years (self-report). * Within 10 years of diagnosis with no evidence of progressive disease or second primary cancers (self-report). * Completed active cancer directed therapy (cytotoxic chemotherapy, radiation therapy and/or definitive surgical intervention) at least six months prior to enrollment; may be receiving "maintenance" therapy to prevent recurrences (self-report). * Body mass index (BMI) of 25-50 kg/m2 Exclusion Criteria: * Type 1 diabetes or currently receiving certain medical treatments for Type 2 diabetes * Report a history of heart attack or stroke within previous 6 months * Health problems which preclude ability to walk for physical activity (e.g., lower limb amputation). Participants endorsing items 1-4 on the Physical Activity Readiness Questionnaire (PAR-Q) (experience of heart problems, frequent chest pains, or faintness or dizziness) will be excluded from the study. * Lost 5% or more of body weight (and kept it off) in the last 3 months * Lifetime history of clinical diagnosis or treatment of eating disorder (anorexia nervosa or bulimia nervosa), OR report of compensatory behaviors within the previous 3 months. If participant reports a history of compensatory behaviors, the investigators will review their information to determine eligibility. * Currently pregnant, pregnant within the past 6 months, or planning to become pregnant within the next 12 months * Untreated thyroid disease or any changes (type or dose) in thyroid medication in last 6 months * Hospitalization for depression or other psychiatric disorder within the past 12 months. * History of psychotic disorder or uncontrolled bipolar disorder * Currently participating in a weight loss, nutrition, or physical activity study or program or other study that would interfere with this study * Currently using prescription medications with known effects on appetite or weight (e.g., oral steroids, weight loss medications), with the exception of individuals on a stable dose of SSRIs for 3 months) * Previous surgical procedure for weight loss or planned weight loss surgery in the next year * Plans for major surgery (e.g., breast reconstruction) in the next 12 months * Inability to speak and read English * Does not reside in the United States * Do not have mobile phone with data plan or willing to be contacted by study through text messaging * No Internet access * Not willing to be randomized to either intervention arm