Skip to main content
OpenTrials
Not Yet Recruiting

NCT Number: NCT07229781

Mediterranean Diet and Blood Sugar Study

The purpose of this research study is to determine if a healthy Mediterranean diet containing one medium potato/day has equivalent or non-different effects on risk factors for type 2 diabetes and heart disease compared to a healthy Mediterranean diet without potatoes in adults with prediabetes. Participants will be randomly assigned to one of the test diets and be asked to consume this diet for 12 weeks (84 days). Testing will be conducted at the beginning and end of the study.

Not Yet Recruiting

Trial opening soon.

Get Notified

Key information

Conditions

PreDiabetes Cardiovascular Diseases Diabetes Mellitus Endocrine System Diseases Glucose Metabolism Disorders Metabolic Diseases Nutritional and Metabolic Diseases Prediabetic State

Age range

25 year–65 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

About this study

This is a 12-week, 2-arm parallel, randomized controlled feeding trial. Participants will be randomized to either a Mediterranean-style diet that includes 1 medium potato/day/2000 kcal replacing some grains , or a traditional-style Mediterranean dietary pattern without potatoes. All food will be provided for the 12-week study duration.

Who can participate

Healthy volunteers accepted: No

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Age 25-65 years
  • Prediabetes assessed by an HbA1c of 5.7-6.4% or fasting glucose 100-125 mg/dL at screening
  • BMI 25-40 kg/m2 at screening

Exclusion criteria

  • HbA1c ≥6.5% at screening
  • LDL-C (calculated with the Martin-Hopkins equation) ≥190 mg/dL at screening
  • Hemoglobin <13.2 g/dL at screening
  • Fasting triglycerides >350 mg/dL at screening

-≥10% change in body weight within the 6 months prior to enrollment

  • Blood pressure >140/90 mmHg at screening
  • Type 1 or type 2 diabetes
  • Prescription of anti-hypertensive, lipid-lowering, or glucose-lowering drugs
  • Intake of supplements that affect the outcomes of interest (i.e., lipid, blood pressure, or glucose lowering; vitamin C or multi-vitamins containing vitamin C) and are unwilling to cease during the study period.
  • History of liver, kidney, or autoimmune disease
  • Prior cardiovascular event (e.g., stroke, heart attack)
  • Current pregnancy or intention of pregnancy within the next 6 months
  • Lactation within the prior 6 months
  • Allergy/intolerance/sensitivity/dislike of any foods in the study menus
  • Antibiotic use within the prior 1 month
  • Oral steroid use within the prior 1 month
  • Use of tobacco or nicotine-containing products within the past 6 months
  • History of cancer at any site within the past 10 years (eligible if ≥10 years without recurrence) or non-melanoma skin cancer within the past 5 years (eligible if ≥5 years without recurrence)
  • Participation in another clinical trial within 60 days of baseline
  • Currently following a restricted or weight-loss diet
  • Prior bariatric surgery
  • Intake of >14 alcoholic drinks/week and/or not willing to avoid alcohol consumption for 48 hours prior to test visits
  • Principal Investigator discretion related to the potential participant's ability to adhere to the study requirements, including being able to come to attend visits
  • Does not speak and/or understand English
  • Unwilling to refrain from donating blood during the study
  • Weight <110 lb

Treatment and study plan

Mediterranean-style diet with potatoes

Other

The diet will contain 1 medium potato/day/2000 kcal

Traditional-style Mediterranean diet

Other

Traditional-style Mediterranean diet higher in grains

Primary outcomes

  1. Change in HbA1c

    Time frame: 12-weeks

    HbA1c will be assessed at baseline and 12-weeks and expressed as percentage . The change in HbA1c will be calculated by subtracting the baseline value from the 12 week value and expressed as percentage point change.

Secondary outcomes

  1. Change in fasting glucose

    Time frame: 12-weeks

    Change in fasting plasma glucose expressed as mg/dL. Change in glucose will be calculated as the mean of the 12 week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  2. Change in mean glucose

    Time frame: 12-weeks

    Change in mean glucose assessed by a continuous glucose monitor (CGM) expressed as mg/dL. Change in mean glucose will be calculated as mean glucose assessed from 7 days of CGM wear at 12 weeks minus mean glucose assessed from 7 days of CGM wear at baseline.

  3. Change in mean time in range

    Time frame: 12-weeks

    Change in mean time in range (glucose 70-140 mg/dL) assessed by a continuous glucose monitor (CGM) expressed as minutes per day. Change in mean time in range will be calculated as mean time in range assessed from 7 days of CGM wear at 12 weeks minus mean time in range assessed from 7 days of CGM wear at baseline.

  4. Change in glycemic variability

    Time frame: 12-weeks

    Change in mean glycemic variability assessed by a continuous glucose monitor (CGM) expressed as the coefficient of variability. Change in mean glycemic variability will be calculated as mean glycemic variability assessed from 7 days of CGM wear at 12 weeks minus mean glycemic variability assessed from 7 days of CGM wear at baseline.

  5. Change in fasting insulin

    Time frame: 12-weeks

    Change in fasting serum insulin expressed as micro IU/mL. Change in insulin will be calculated as the mean of the 12 week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  6. Change in homeostatic model of insulin resistance (HOMA-IR)

    Time frame: 12-weeks

    Homeostatic model of insulin resistance (HOMA-IR) will be calculated from insulin and glucose measured from a fasting blood sample. Calculated as (insulin × glucose) / 22.5. Change in HOMA-IR will be calculated as the mean of the 12 week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  7. Change in LDL-Cholesterol

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/dL. Change in LDL-cholesterol will be calculated as the mean of the 12-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  8. Change in apolipoprotein B

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/dL. Change in apolipoprotein B will be calculated by subtracting the baseline value from the 12 week value.

  9. Change in non-HDL cholesterol

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/dL. Change in non-HDL cholesterol will be calculated as the mean of the 12-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  10. Change in Total Cholesterol

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/dL. Change in total cholesterol will be calculated as the mean of the 12-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  11. Change in HDL-Cholesterol

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/dL. Change in HDL-cholesterol will be calculated as the mean of the 12-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  12. Change in Triglycerides

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/dL. Change in triglycerides will be calculated as the mean of the 12-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  13. Change in C-reactive protein

    Time frame: 12-weeks

    Assessed from fasting blood draw expressed in mg/L. Change in C-reactive protein will be calculated as the mean of the 12-week measures (i.e., mean of day 1 and day 2 values) minus the mean of the baseline measures (i.e., mean of day 1 and day 2 values).

  14. Change in Central Systolic and Diastolic Blood Pressure

    Time frame: 12-weeks

    Central blood pressure measured assessed using a SphymoCor Xcel (Atcor Medical) at baseline & 12 weeks. Change will be calculated by subtracting the baseline value from the end point value.

  15. Change in Peripheral Systolic and Diastolic Blood Pressure

    Time frame: 12-weeks

    Peripheral blood pressure measured assessed using a SphymoCor Xcel (Atcor Medical) at baseline & 12 weeks. Change will be calculated by subtracting the baseline value from the end point value.

  16. Change in Carotid-Femoral Pulse Wave Velocity

    Time frame: 12-weeks

    Measured assessed using a SphymoCor Xcel (Atcor Medical) at baseline & 12 weeks. Change will be calculated by subtracting the baseline value from the end point value.

  17. Change in particle size and number of LDL, HDL, triglyceride rich lipoproteins

    Time frame: 12-weeks

    Measured via Nuclear Magnetic Resonance

  18. Diet Satisfaction

    Time frame: 12-weeks

    Participants will complete a survey that we have previously developed to assess diet satisfaction at 12 weeks.

Study contacts

Contact information is provided by the study sponsor or research team.

Kristina Petersen, PhD

CONTACT

[email protected]

814-865-7206

Stacey Meily

CONTACT

[email protected]

814-863-8622

Sponsors and collaborators

Lead sponsor

Penn State University

Other

Collaborators

  • Alliance for Potato Research & Education

Registry information

Official study title

Glycemic Effects of a Mediterranean-Style Dietary Pattern Containing Potatoes in Adults With Prediabetes

Important dates

Study start
2026
Primary completion
2028
Study completion
2028
First posted
Nov 17, 2025
Registry last updated
Jul 15, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

Related clinical trials

Published trials that share one or more normalized conditions with this study.