The purpose of the ENERGY trial is to explore whether two different programs that are focused on weight management, through increased exercise and a healthy diet, are feasible, and have an impact on body weight, quality of life and fatigue. Since obesity among breast cancer survivors is associated with recurrence and other co-morbidities, those will be assessed and their impact calculated. Blood samples will be collected to enable analysis of potential mechanisms and differential response across subgroups.

Inclusion Criteria:

• Diagnosis of breast cancer (stages I (≥1 cm), stage II, or stage IIIA, B, C excluding distant metastasis) diagnosed between 6 months and 5 years earlier; after initial therapies are completed, diagnosed between six months and five years earlier
• BMI between 25 to 45 kg/m2
• Able to comply with all required study procedures and schedule

Exclusion Criteria:

• Serious medical condition or psychiatric illness
• Inability to be moderately physically active
• Obesity of known endocrine origin (e.g., untreated hypothyroidism, PCOS)
• Currently enrolled in a weight loss program
• Current use of weight loss medication or supplements
• Previous surgical procedures for weight reduction
• Planning weight loss surgery in the next 2 years.
• 6+ months use of meds likely to cause weight gain or prevent weight loss
• Planned surgical procedure that can impact the conduct of the study
• Currently pregnant/breastfeeding
• Planning to become pregnant within the next 2 years
• Have plans to relocate from area within 2 years
• Family relative or close friend is a trial staff member or a study participant
• Any condition which in the opinion of the investigator makes the subject unsuitable for inclusion in this study