A Low-Insulinemic Dietary Intervention to Reduce Breast Cancer Risk in High-Risk Women

Inclusion Criteria:

* Age ≥ 45 years OR post-menopausal AND cis-gender women at study registration.
* Overweight or World Health Organization (WHO) class 1 obese as defined by a body mass index (BMI) of 25 to 35 kg/m\^2.
* High risk for breast cancer at the discretion of the physician, using standard definitions such as a Gail 5-year risk of ≥ 2% or Tyrer Cuzick version (v) 8.0 10-year risk of ≥ 5%.
* Concurrent or prior use of endocrine therapy is allowed. Any dose or schedule change is not permitted for the duration of the study.
* Currently established care or previously seen at the Ohio State University Comprehensive Cancer Center (OSUCCC) Stefanie Spielman Comprehensive Breast Center (SSCBC) high risk breast clinic.

Exclusion Criteria:

* Prior diagnosis of breast cancer within past 5 years.
* Metastatic breast cancer (at study start or during study period).
* BMI \> 35 kg/m\^2 or \< 25 kg/m\^2.
* Pre-menopausal women or \< 45 years of age.
* Assigned male at birth.
* Uncontrolled intercurrent illness including lung disease, heart disease, metabolic disease; exacerbations for disease in past 8 weeks; unstable on medications for chronic conditions in past 6 weeks. This could affect compliance and engagement with study intervention. Change in anti-hyperglycemic or lipid lowering medications is best avoided for the duration of the study unless deemed necessary by treating provider or required for acute exacerbation of existing illness.
* Type 1 diabetes mellitus (DM) or insulin dependent, or evidence of brittle diabetes.
* Presence of food allergies or intolerances to wheat, nuts, seeds, fish, or dairy foods.
* Currently on special diet for known metabolic or gastrointestinal disease, or planning to start a specific dietary regimen such as vegetarian, vegan, ketogenic, low-fat diets, etc.
* Uncontrolled psychiatric illness/social situations that would limit compliance with study requirements.
* Unwilling or unable to follow protocol requirements.
* Pregnant, trying to get pregnant, or nursing.
* Any condition which in the investigator's opinion deems the subject an unsuitable candidate to participate in this study.
* Non-English speaking, as the teaching materials and educational sessions have not yet been translated into additional languages.
* Prisoners or other institutionalized patients.