This research will test whether a Dietary Approaches to Stop Hypertension (DASH) or a very low-carbohydrate diet better improves outcomes like blood glucose control and body weight for adults with polycystic ovary syndrome.

Participants will have screening (includes blood draw) and baseline testing with a continuous glucose monitor and a body composition scan (called a dual-energy x-ray absorptiometry or DEXA). Once these enrollment steps are completed and the participants will be randomized to one of two 12-month programs.

Inclusion criteria:

• Participants must have the following criteria:

  • oligomenorrhea-anovulation

    • spontaneous intermenstrual periods (if not on hormonal birth control or birth control that alters menstrual cycle timing) of < 21 days or > 35 days or a total of 8 or fewer menses per year
    • if on hormonal birth control or birth control that alters menstrual cycle timing, a history of irregular periods

  • and hyperandrogenism

    • If not on hormonal birth control or birth control that alters menstrual cycle timing: Total testosterone ≥ 35 ng/dL OR free testosterone > 4.0 pg/ml OR free androgen index > 1.5 OR in-person scoring for hirsutism, based on the modified Ferriman-Gallwey score, if attending an in-person assessment or based on the self-assessment (if not attending an in-person assessment) with a score of ≥ 4 considered hirsutism;
    • If on hormonal birth control or birth control that alters menstrual cycle timing: Tests within the past 10 years showing the above or study team's in-person assessment of hirsutism as above.

• If no medical records to confirm (most recent test from within the last 10 years in range), tests for diagnosis will be ordered:

  • total testosterone < 100 ng/dL,
  • dehydroepiandrosterone sulfate (DHEAS) < 600 μg/dL,
  • fasting 17-hydroxyprogesterone (17-OHP) level < 2.0 ng/mL,
  • prolactin < 25 ng/ml),
  • follicle-stimulating hormone (FSH) levels < 20 mIU/mL

• BMI 25-50 kg/m2 or 23-50 kg/m2 for Asians

• Access to internet

• Ability to engage in light physical activity

• Willingness to be randomized to either dietary approach

• Measured HbA1c at baseline of 5.3%-9.0%

Exclusion criteria:

• Primary

  • Patients with non-PCOS etiologies of anovulation and hyperandrogenism (Cushing's disease, thyroid dysfunction, elevated prolactin levels, signs of a congenital adrenal hyperplasia organic intracranial lesion like a pituitary tumor, or suspected adrenal or ovarian tumor secreting androgens)
  • Menopause or removal of the ovaries
  • history of type 1 diabetes
  • use of medications prescribed for weight loss or psychostimulants known to affect weight
  • participation in another weight loss program or intervention
  • use of glucose lowering medications other than metformin or medications known to affect metabolism, such as chronic oral corticosteroids
  • pregnant or planning to become pregnant during the intervention period
  • Breastfeeding or less than 6 months postpartum
  • previous bariatric surgery or planning to have bariatric surgery during the study period
  • Self-reported blood disorders that influence HbA1c, including frequent blood transfusions, phlebotomy, anemia, hemoglobinopathy, and polycythemia

• Ability

  • inability to read, write, or speak English
  • inability to provide informed consent
  • adherence to a vegan or vegetarian diet
  • difficulty chewing or swallowing
  • no influence over what foods are purchased, prepared, and/or served or inability to follow dietary advice due to lack of money or other resources
  • above weight limit (500 lbs) for DEXA
  • self-report of alcohol or substance use disorder within the past 5 years, including current at-risk drinking based on an AUDIT score of 15 or higher (but those who score a 15 or higher and have this criterion as their only reason for ineligibility may be assessed by a clinical psychologist for alcohol use disorder and if deemed to not have such a disorder would be eligible for the trial)

• Safety

  • Renal disease: BUN > 30 mg/dL or serum creatinine > 1.4 mg/dL in our screening blood tests or history of kidney stones

  • untreated eating disorder or unstable serious mental illness (such as depression (score of 20 or greater on the PHQ8), bipolar or schizophrenia with psychosis)

  • use of warfarin

  • chronic kidney disease, stage 4 or higher

  • Any other concerning values in baseline labs (we will plan to send the participant to their PCP and allow the participant to return for later enrollment if labs are no longer concerning) Examples:

    • triglycerides of 600 mg/dL or higher
    • baseline uncorrected thyroid disease: TSH < .45 mIU/ML or > 4.5 mIU/ML
    • potassium: any abnormal value
    • baseline aspartate aminotransferase (AST) or alanine aminotransferase (ALT) > 2 times normal

  • any condition for which the study team deems participation to be unsafe or inappropriate

Outcome assessment and data analysis will be masked