Low participant compliance, slow recruitment

This is a randomized controlled trial of a 6-month extreme carbohydrate restricted diet (20 grams total carbs/day) via phone counseling with dietitian plus aromatase inhibitor therapy vs. 6-month control with aromatase inhibitor therapy alone. Visits will occur at screening, 3 months, and 6 months. Anthropomorphic measurements (such as heart rate, weight, and body measurement) and questionnaires will be taken at all three visits. After screening, patients will be randomized to receive the carbohydrate restricted diet coaching immediately (Arm A) or to a control group (Arm B). Patients randomized to Arm A will receive weekly calls for the first 3 months of the intervention, then biweekly calls for the last 3 months of the intervention from the study dietitian. Total duration of the study is expected to be 3 years, though each patient's participation will be approximately 6 months.

Inclusion Criteria:

• Histologically confirmed breast cancer

• Planning to start adjuvant hormonal therapy using an aromatase inhibitor or has started adjuvant hormonal therapy using an aromatase inhibitor

• Able to read, write, and understand English

• BMI ≥ 24 kg/m2

• Age ≥ 18 years

• ER and/or PR positive (defined as having ≥ 1% staining for ER and/or PR on IHC)

• Post-menopausal

  • The absence of menstrual cycles in women who have not undergone hysterectomy for at least 12 months preceding cancer diagnosis OR
  • History of a bilateral oophorectomy OR
  • History of a hysterectomy and age >55 OR
  • No menses for <1 year with FSh and estradiol levels in postmenopausal range according to institutional standards

• ECOG Performance Status 0 or 1

• Female

• Written informed consent obtained from subject and ability for subject to comply with requirements of the study

Exclusion Criteria:

• Use of hormonal therapy other than aromatase inhibitors
• History of other malignancy within the past 5 years, except for malignancies with a > 95% likelihood of cure (e.g. thyroid cancer, non-melanoma skin cancer)
• Already consuming a severe carbohydrate restricted (<20 g carbohydrates per day) diet or vegetarian diet
• Currently on or plans to start chemotherapy (HER2/neu targeted therapy okay)
• Medical comorbidities that in the opinion of the investigator limits the patient's ability to complete the study
• Symptomatic metastases (Metastases allowed if asymptomatic)
• Current use of appetite suppressant medications
• Current use of any weight loss medications including herbal weight loss supplements or if patients are enrolled in a diet/weight loss program