Inclusion Criteria:

          -  All participants must provide written informed consent.

          -  Patients must have histologically confirmed primary invasive mammary carcinoma

               -  The tumor must be estrogen receptor positive

               -  The tumor must be HER2 negative (negative IHC or FISH)

               -  The primary tumor size must be reproducibly measurable by physical examination
                  and/or ultrasound and at least 1 cm in size.

          -  Patients must be post-menopausal defined by any of the following:

               -  Subjects at least 55 years of age.

               -  Subjects younger than 55 years of age and amenorrheic for at least 12 months or
                  serum follicle-stimulating hormone (FSH) levels >= 40 IU/L and estradiol levels
                  <= 20 IU/L.

               -  Subjects with history of bilateral oophorectomy or prior radiation castration
                  with amenorrhea for at least 6 months.

          -  Patients must have clinical stage I, II, or III invasive mammary carcinoma planning to
             undergo surgical treatment with either segmental resection or total mastectomy.

          -  Patients must have BMI >= 30.

          -  A core biopsy from the time of diagnosis must be available.

          -  Mammogram or ultrasound required within 3 months of screening

          -  Patients must have adequate organ function based on the following laboratory
             parameters:

               -  Serum creatinine <= 1.5x ULN

               -  SGOT, SGPT <= 4x ULN (unless known steatohepatitis)

               -  Serum albumin >= 2.0 g/dL

               -  Total serum bilirubin <= 1.5x ULN (or <= 3x ULN if known Gilbert's syndrome)

        Exclusion Criteria:

        Patients with locally advanced disease who are candidates for other preoperative
        (chemo)therapy at the time of initial evaluation. This includes patients with inflammatory
        breast cancer.

          -  Locally recurrent breast cancer.

          -  Evidence of distant metastatic disease (stage IV).

          -  Serious medical illness that in the judgment of the treating physician places the
             patient at high risk of operative mortality.

          -  Serious medical illness that in the judgment of the treating physician would preclude
             the use of a ketogenic diet.

          -  Severe uncontrolled malabsorption condition or disease (e.g. grade II/III diarrhea,
             severe malnutrition, short gut syndrome).

          -  Diabetes mellitus requiring insulin therapy.

          -  Dementia, altered mental status, or any psychiatric condition that would prohibit the
             understanding or rendering of informed consent.

          -  Participation in any other neoadjuvant therapeutic clinical trial.

          -  Concurrent anti-cancer therapy other than endocrine therapy (e.g. chemotherapy,
             radiotherapy, immunotherapy, or any other biologic therapy).

          -  Concurrent treatment with an investigational agent.

          -  Use of an investigational drug within 30 days or 5 half-lives, whichever is longer,
             preceding the first day of dietary intervention.