Explanation for the choice of comparators

The study will compare the effects of two diets on glucose regulation and PCOS symptoms: a very low-carbohydrate (VLC) diet and the Dietary Approaches to Stop Hypertension (DASH) diet. The diets vary in their approach to regulating insulin levels, glucose control, and weight loss, which are key targets for managing symptoms of PCOS [24,25,26]. Both diets have been recommended by groups of healthcare professionals as nutrition advice for women with PCOS, but experts disagree on which diet is best practice for nutrition advice to manage PCOS [17, 18, 20]. The study aims to address this knowledge gap by providing rigorous, long-term data comparing the diets’ effects on glucose control and PCOS symptoms.

Intervention description

Participants will follow either the VLC or DASH diet for 12 months with guidance from a diet coach and 24 pre-recorded video sessions. They will be able to email their coaches at any time with questions, and they will have the option to attend monthly group video calls. Participants will also be able to request one-on-one calls with their coach at any time during the program. Regardless of how often participants reach out to their coaches, the coaches will reach out to each participant via email at least once biweekly during the program.

The participant will receive videos, informational handouts, and check-in surveys on a weekly basis for the first 4 months. Thereafter, they will receive videos and handouts monthly, and the check-in surveys will be distributed biweekly. The videos and handouts will teach about the assigned diet, skills to cope with stress and changing one’s diet, mindful eating and exercises to improve self-awareness, and information about PCOS and theory of the diet’s physiological influence on the condition. The surveys will ask questions about the participant’s dietary adherence, side effects and symptoms, program enjoyment, medication changes, and pregnancy status. To facilitate their transition to the new diet, participants will receive cookbooks throughout the study that correspond to their assigned diet. Participants will receive motivational texts and will be encouraged to self-monitor their eating patterns through food tracking and weighing themselves on a standard scale provided by the study throughout the intervention.

Very low-carbohydrate diet

The VLC diet aims to reduce carbohydrate intake to 20–35 g of non-fiber carbohydrates daily. Most calories are derived from meat, fish, eggs, fats, nuts, seeds, oils, leafy or other low-carbohydrate vegetables (such as spinach, lettuce, asparagus, eggplant, cabbage, kale, brussels sprouts, green peppers, and green beans), and low-carbohydrate fruits (such as raspberries and blackberries). Participants are advised to eliminate most starches and sweets such as potatoes, rice, pasta, bread, donuts, and sugar-sweetened beverages. Participants will be asked to avoid dairy. Participants will be advised to eat a moderate amount of protein with each meal and derive their remaining calories from fat.

The VLC diet is designed to lower carbohydrate intake to a point that induces a low level of ketone production. Nutritional ketosis may serve as a marker indicating that insulin levels are reduced enough to allow the body to begin using fat as a key source of energy, reducing inhibition of lipolysis by insulin. When this occurs, some fats are turned into ketones, which serve as a readily used fuel [18]. Participants randomized to this diet group are mailed urine ketone strips. They will be encouraged to use ketone urine test strips at the beginning of their time following this dietary approach to help them gauge whether they are achieving nutritional ketosis.

DASH diet

The DASH diet is recommended by some experts for management of weight and glucose control in women with PCOS [17]. It is a low-fat (20–30% of daily calories) and low-sodium (< 2300 mg daily) diet in which participants will be encouraged to eat fruits, vegetables, low-fat dairy foods, whole grains, lean meat and fish, and foods with little to no sugar, saturated fats, or oil. Participants will be taught about serving sizes and the appropriate number of servings to consume per day. The DASH diet is designed to lower the consumption of calories and saturated fat as the method for weight loss.

Physical activity goals

Participants will be encouraged to engage in physical activity that they enjoy for an average of 15–30 min per day. This recommendation is adapted from current guidelines for people with PCOS [35] and for diabetes prevention [36], which recommends 150 min of exercise per week.

Behavior goals

The primary behavior goal for this study is dietary adherence. The study is designed to encourage dietary adherence through support and education from coaches and through teaching ways of thinking that promote intentional eating habits. Mindfulness and positive affect will be taught through the sessions as optional behavior goals.

Criteria for discontinuing or modifying allocated interventions

Serious adverse events resulting from the intervention are not expected. If a serious adverse event occurs, participants will stop the intervention immediately and will be included in the intention-to-treat analysis for the primary endpoint. Criteria for discontinuing or modifying the intervention include changes in the therapeutic plan of participants, such as new weight loss medications (other than metformin) or other medications that are not permitted; starting SGLT-2 inhibitors, as they increase the risk of ketoacidosis; the development of other concerning conditions such as severe depression or an untreated thyroid condition; or a positive pregnancy test. Participants are informed that they may refuse to answer any questions asked as part of the outcome measures by the study team and that they may withdraw their consent to participate in the study at any time.

Strategies to improve adherence to interventions

Both dietary programs include strategies to improve adherence, including mindfulness, encouragement, and reminders, and tips for seeking support from loved ones. These are listed under psychological topics in Table 2.

Relevant concomitant care permitted or prohibited during the trial

Participants will be instructed to work with their primary care providers about any existing issues, and primary care providers will be informed of this trial, as well. For all eligible participants, all blood test results will be sent to participants, and they will be advised to share blood test results with their primary care providers throughout the study.

Some side effects can be expected when changing one’s diet or losing a significant amount of weight. Participants may be directed to their primary care providers if symptoms are long lasting or are not able to be self-managed. Possible side effects include constipation, headaches, muscle cramps, bloating, dizziness, rash, hypoglycemia, hyperlipidemia, hypotension, kidney stones, and hair loss. All participants receive educational materials that will describe symptom self-management. They are asked to report symptoms in their check-in surveys to monitor for concerning side effects.

It is expected that some participants from either group may advance to type 2 diabetes while on this trial. If primary care providers decide to start their patient on glucose-lowering medications (except SGLT-2 inhibitors), those participants will be allowed to remain in the trial. Participants who start SGLT-2 inhibitors will be removed from the trial due to concerns for increased risk of ketoacidosis. Study physicians will use their judgement to determine if participants must be removed from the trial due to the development of other exclusionary diagnoses, etc.

Depression is common in women with PCOS. We assess depressive symptoms at baseline, month 4, and month 12. Participants with severe depression (a score of 20 or greater on the PHQ-8 during the screening survey) are ineligible and are referred to mental health resources. Participants with any PHQ-8 score between 10 and 20 are eligible but will also be referred to mental health resources. Participants with any PHQ-8 score below 10 are not referred to mental health resources, as the intervention itself contains positive affect skills which have been found to be effective for helping people with elevated depression, such as in a previous trial of the PIs [37]. If participants mention severe depression or suicidal ideation throughout the trial, a clinical psychologist will provide triage evaluation.

Provisions for post-trial care

We will not provide post-trial care. We do not anticipate harm and therefore no compensation for harm due to trial participation.

Outcomes Primary outcome HbA1c

According to standards for type 2 diabetes clinical care, HbA1c is the most widely accepted measure of overall glycemic control [38]. We aim to understand how these diets impact overall glycemic control via measurement of HbA1c, as people with PCOS are at greater risk for insulin resistance, poor glycemic control, and development of prediabetes or type 2 diabetes [9]. We measure HbA1c levels using standard immunoturbidimetric assay methods and quality control measures at a Clinical Laboratory Improvement Amendments (CLIA) certified lab (i.e., Labcorp). Our primary outcome is change in HbA1c from baseline to 12 months, and our secondary outcome is change in HbA1c from baseline to 4 months.

Secondary outcomes Conversion to normoglycemia

Of critical concern is whether participants can convert to normoglycemia, having an HbA1c level of < 5.7%. In addition to measuring overall change in HbA1c, we record whether participants have converted to or maintained normoglycemia at the 4- and 12-month marks.

Glycemic variability

Greater glycemic variability may lead to complications [39], and intraday blood glucose variability is greater in people with prediabetes compared to people with normal glycemic levels [40]. We use continuous glucose monitors to compare measures of glycemic variability at baseline and 12 months. For in-person participants, we place a blinded Abbott Libre Pro continuous glucose monitoring device on a patient’s upper arm and will instruct participants to leave the monitor on for 14 days. Others are given the option to place a continuous glucose monitor at home with the assistance of a trained staff member on a video call.

Serum insulin and insulin resistance

Fasting insulin and glucose are used to calculate Homeostatic Model Assessment-Insulin Resistance (HOMA-IR). We measure fasting insulin and glucose at baseline, 4 months, and 12 months using standard assays from LabCorp to determine HOMA-IR, a widely used method of estimating insulin resistance from a single fasting blood draw [41].

High sensitivity to C-reactive protein

High sensitivity C-reactive protein (hsCRP) is an important acute inflammation protein and measure of inflammation which is associated with increased risk of cardiovascular disease [42]. Increased inflammation is associated with metabolic syndrome, and emerging evidence suggests that it may be a factor in the development of macrovascular disease in type 2 diabetes, which is more likely in patients with PCOS [43]. Beta hydroxybutyrate, the ketone body that is most abundant in the blood in patients following a ketogenic diet, has been shown to inhibit inflammation by disrupting the inflammatory response [44, 45]. A ketogenic diet is also associated with a reduction of reactive oxygen species, which are linked to inflammatory diseases [46]. We assess hsCRP using standardized methods in a CLIA certified laboratory (Labcorp).

Lipids

The ketogenic diet increases the proportion of calories derived from fat compared to a conventional diet such as the DASH diet. The greater intake of fat has prompted concerns about the effects of a ketogenic diet on blood lipids, especially LDL cholesterol. We aim to understand the possible impact of the ketogenic and DASH diets on macrovascular health in PCOS, and we include measurements of triglycerides and major plasma lipid fractions (HDL, LDL, triglycerides). We measure triglycerides and fractionated cholesterol using Labcorp’s Nuclear magnetic resonance (NMR) LipoProfile [47]. This advanced lipid assay provides measures that are more tightly tied to elevated cardiovascular risk than conventional lipid assays [48].

Body composition

Weight loss may involve the loss of lean body mass, fat body mass, or both, and each form of weight loss has a different association with health outcomes. In particular, a lower proportion of lean to total body mass is associated with greater mortality [49]. For participants local to Michigan, we measure body composition using Dual-Energy X-ray Absorptiometry (DEXA) scans.

PCOS symptoms

At baseline and at 4 and 12 months later, we will assess PCOS-related quality of life using the PCOSQ [50], acne using the Global Acne Severity Scale (Global Evaluation of Acne, or GEA scale) [51] hirsutism using a modified version of the Ferriman-Gallwey score [52], and cycle regularity through participant reports on cycle length, duration, and frequency.

Other assessments Health-related quality of life

At baseline and at the 4- and 12-month checkpoints, we assess health-related quality of life using the PROMIS-29. This instrument is a collection of 4-item measures for broad domains of health-related quality of life including anxiety, depression, fatigue, pain interference, physical function, sleep disturbance, and ability to participate in social roles and activities, as well as a single pain intensity item [53].

Diet-related symptoms

We monitor for possible side effects throughout the trial. At baseline and at 4 and 12 months, we will also assess physical symptoms using a self-report scale.

Dietary adherence and changes

We assess dietary adherence with one unannounced 24-h dietary recall at baseline, 4, and 12 months. For each recall, we measure the number of calories consumed of each macronutrient and the percent that each contributes to total calories. For participants in the low-carbohydrate group, blood ketone levels are a biomarker to help assess whether target levels of carbohydrate restriction have been achieved. We assess fasting β-hydroxybutyrate at baseline, 4 months, and 12 months for all participants.

Session attendance and study dropout

We track attendance by monitoring whether participants have opened their session emails and whether they have completed their check-in surveys. Participants are considered dropouts if they ask to be withdrawn from the trial (or if they have been removed from the trial for any reason).

Program satisfaction

Using the Client Satisfaction Questionnaire [54], we assess intervention satisfaction at 4 and 12 months. It asks questions such as, “Which parts of the program have been most helpful to you?” and “On a scale from 0 to 10, how likely would you be to recommend our program to other people you know with PCOS?”.

Qualitative exploration of participants’ perspectives

We conduct optional qualitative semi-structured interviews with participants at 4 and 12 months after baseline. Interviews explore participant experiences, particularly their perceptions of the barriers to and facilitators of their ability to make long-lasting dietary changes.

Weight

Moderate weight loss is associated with improved glycemic control in type 2 diabetes [55]. Local participants are weighed at their in-person DEXA appointments at baseline and 12 months. At 0, 4, and 12 months, we collect measurements from their home scale that was provided by the study. The participants who do not come to the in-person appointments only have weight measurements from the home scale provided by the study.

Moderators Body mass index

We will measure participants’ height and weight at baseline and 12 months and assess change in BMI.

Participant timeline Screening and enrollment procedures

Enrollment occurs on a rolling basis. Participants who were ineligible for prior recruitments based on their blood work may be retested for eligibility later. Eligible participants start the program on the Sunday after they are randomized.

Participants are directed via recruitment materials and the study website to a screening survey through the online platform REDCap. The screening survey briefly describes the trial, asks for limited consent, and asks questions to obtain information regarding inclusion and exclusion criteria. The survey contains contact information for the study staff so that potential participants may contact the study team with any questions. The study staff follow up with potentially eligible participants via email, and they ask questions to verify eligibility. For any participant who scores greater than or equal to a ten on the PHQ-8, we will provide an automatic message directing them to mental health resources.

Participants who are determined to be potentially eligible based on the screening survey receive a study orientation video from the study team via email. The video gives a brief overview of the study interventions, procedures, and the expectations of participants. The video is followed by a short survey to assess comprehension, and a consent form to be reviewed and signed by the participant to move forward with a blood draw screening (described below).

After signing a consent for a baseline blood draw, participants receives an order for the following lab tests at their local Labcorp location: (1) total testosterone*; (2) free testosterone; (3) sex hormone-binding globulin; (4) comprehensive metabolic panel (Albumin, Albumin/Globulin Ratio (calculated), Alkaline Phosphatase, ALT, AST, BUN/Creatinine Ratio (calculated), Calcium, Carbon Dioxide, Chloride, Creatinine with GFR Estimated, Globulin (calculated), Glucose, Potassium, Sodium, Total Bilirubin, Total Protein, Urea Nitrogen); (5) thyroid-stimulating hormone (TSH); (6) HbA1c; (7) fasting insulin; (8) high-sensitivity C-reactive protein; (9) NMR LipoProfile with lipids; (10) beta hydroxybutyrate (ketone, important for VLC diet); (11) follicle-stimulating hormone (FSH); (12) estradiol; (13) luteinizing hormone (LH); (14) prolactin*; (15) dehydroepiandrosterone sulfate* (DHEAS); and (16) fasting 17-hydroxyprogesterone* (17-OHP). Tests marked with an asterisk will only be taken for individuals who are not on hormonal birth control because the hormone levels may be altered as a result of taking hormonal birth control. The participants who are taking hormonal birth control are required to have the necessary lab results for the tests marked above with an asterisk from within the past 10 years (when they were not using hormonal birth control).

If the participant’s blood draw data meet the inclusion criteria, the participant attends a virtual visit with a trained study team member to complete the full study informed consent. The study team member gives the participant a detailed review of the study, including procedures, expectations, risks, and benefits. The team member clearly explains that study participation is completely voluntary and that the participant may leave the study or refuse to participate at any time. Individuals who are still interested in the study upon reviewing the consent document with the study team member provide written informed consent using REDCap, and the team member helps the participant schedule their in-person appointment for follow-up testing. The study team member collects other information during the call, including availability for 24-h dietary recall phone calls. Participants may also consent to additional, optional research tasks during the visit, including optional, audio-recorded qualitative interviews at 4 and 12 months.

Baseline measurements and procedures

After completing the trial consent visit, participants are invited to complete baseline assessments before being randomization to one of the two diet groups.

Participants who live within driving distance of Ann Arbor attend an appointment at the Michigan Diabetes Research Center’s Clinical Research Unit, where the following assessments and procedures will be performed:

Pregnancy test, which must be negative to proceed with enrollment

DEXA scan

Modified Ferriman-Gallwey score test for hirsutism

The GEA scale

Body weight and height

Placement of a continuous glucose monitor (CGM), which is worn for 14 days and mailed back to the study team. The CGM does not give feedback to the participant, so they are blinded to the results. Per the instructions for the Libre Sensors being used, participants are instructed to not take more than 500 mg of vitamin C per day or more than 650 mg of aspirin per day while wearing the sensor during the study period.

Participants who are not in driving distance of Ann Arbor do not have an in-person appointment. They complete the following assessments and procedures at home:

Body weight and self-reported height

Optional at-home GEA scale exam using photos and video of the face

Optional self-placement of a CGM with the assistance of a trained staff member on video call.

All participants receive an unannounced phone call from a study team member performing a 24-h dietary recall, in which the participant reports everything they ate the day prior. They also complete an online baseline survey that measures health-related quality of life, reward-based eating, and exercise habits.

The study team informs primary care providers and specialists (as needed) about the patient’s participation in this trial via a HIPAA-compliant fax. Primary care providers are asked to respond within 2 weeks of receiving the message if they believe that it is unsafe for the participant to move forward with the study. If the primary care provider does not respond or says that participation is acceptable, then the participant may move forward with the study. The primary care providers are notified that participants are expected to work with them to manage medications and preexisting issues, and they are informed that participants may come to them with side effects and blood test results from the study.

Participants are randomized to either diet upon completion of all assessments and activities listed above. Randomization is conducted using a computer-generated permuted block randomization process for well-balanced assignments and minimized ability to anticipate assignment. Although treatment condition is apparent to participants and researchers, outcome assessment and data analysis are masked. We stratify by baseline HbA1c: less than 6.5% or 6.5 and higher.

Interventions

The participants receive body weight scales in the mail. These scales automatically provide the study team with weights taken with no set up required by the participant. Once randomized, participants in the VLC group also receive ketone strips to test for urinary ketones at certain points in the study. The intervention begins the Sunday after a participant is randomized. They are sent the pre-recorded videos, reading materials, check-in survey, and home assignments via email on a weekly basis for the first 4 months, and monthly thereafter. The class content for each weekly and monthly session is detailed in Table 1. Participants have the opportunity to set up one-on-one calls with the diet coach and to attend group question and answer sessions with the coach. Coaches email participants at least biweekly.

Table 1 Session schedule for common elements in both intervention arms

At month 4, participants complete the following measures:

One dietary recall over the phone

An online survey (same as the baseline survey with the addition of program satisfaction questions)

Body weight on a scale at their home

A fasting blood draw as described in the baseline assessments

At month 12, participants complete the above measures in addition to:

For participants that live within driving distance to Ann Arbor, an in-person visit with the same measures and procedures as the baseline in-person visit.

For participants who do not live within driving distance of Ann Arbor, the same body weight and height measurements and optional CGM placement as the baseline procedures.

At months 4 and 12, participants are offered the opportunity to complete an optional interview to explore their experience with their assigned diet and the program. Interviews take place over Zoom and are audio-recorded and transcribed.

Upon completion of the 12-month tasks, the participant has completed the program. They are instructed to continue their management of their condition with their healthcare team.

Figure 1 shows the SPIRIT figure with the schedule of enrollment, interventions and assessments. Table 2 shows when participants complete these and other measures in the trial.

Fig. 1

Schedule of enrollment, interventions, and assessments

Table 2 Summary of measures by aim and month