Effects of a Mediterranean Diet With Cycling and Rowing Exercise on Blood Sugar in Women With Prediabetes

This study aims to investigate the effects of a Mediterranean-style diet combined with cycling and rowing exercises on blood sugar control and daily blood sugar fluctuations in women with prediabetes.

Prediabetes is a condition in which blood sugar levels are higher than normal but not high enough to be diagnosed as type 2 diabetes. Importantly, prediabetes can often be reversed with appropriate lifestyle changes. Healthy eating habits and regular physical activity are the most effective ways to prevent the progression from prediabetes to diabetes. However, commonly used blood sugar tests, such as fasting glucose and hemoglobin A1c (HbA1c), do not always reflect daily ups and downs in blood sugar levels.

For this reason, this study will use continuous glucose monitoring (CGM) in addition to standard blood tests. CGM is a small sensor placed on the upper arm that measures blood sugar levels continuously throughout the day and night. This method shows how long blood sugar stays within a healthy range and how much it fluctuates during daily life. These detailed measurements allow a more accurate evaluation of how diet and exercise affect blood sugar control.

One important feature of this study is that it examines not only the effect of diet but also the effects of two different types of exercise. Participants will first perform cycling exercises, which mainly involve the lower body, and then rowing exercises, which engage both the upper and lower body. This approach allows a comparison of how different exercise types influence blood sugar regulation. In addition, evaluation will be based on metabolic background.Women whose blood sugar levels have recently returned to normal will be compared with women who still have prediabetes to determine whether responses differ to the same lifestyle program.

The study will last 12 weeks and will include three groups based on blood sugar status and medical suitability for exercise. The diet-only group will consist of women with prediabetes who are not able to participate in structured exercise for medical reasons and will follow a Mediterranean diet for 12 weeks. The diet plus exercise group will include women with ongoing prediabetes who are medically able to exercise; these participants will follow the Mediterranean diet and perform supervised exercise three times per week for 8 weeks. The third group will consist of women who were diagnosed with prediabetes within the last year but whose blood sugar levels are normal at the start of the study. This group will follow the same diet and exercise program as the second group.

The Mediterranean diet used in this study emphasizes vegetables, fruits, whole grains, legumes, olive oil, and fish, while limiting processed foods and red meat. All participants will receive individual nutrition counseling from a dietitian, and dietary adherence will be monitored regularly.

Exercise programs will be personalized for each participant. Exercise intensity will be determined using a standard exercise test performed at the beginning of the study to measure maximum heart rate. During all exercise sessions, heart rate will be continuously monitored using a chest strap to ensure safe and effective training. All exercise sessions will be conducted under professional supervision at the Faculty of Sport Sciences at Marmara University.

Throughout the study, participants' health status will be evaluated using multiple methods. The main goal is to determine how many participants achieve normal blood sugar levels by the end of the 12-week period. Blood tests will include fasting glucose, an oral glucose tolerance test (OGTT), and HbA1c. In addition, participants will wear a Dexcom G7 continuous glucose monitor during four separate 10-day periods while continuing usual daily activities.

Body weight, waist circumference, and body fat percentage will be measured at regular intervals. Sleep quality and adherence to the Mediterranean diet will be assessed using validated questionnaires.

The collected data will be analyzed to compare changes in blood sugar patterns between the different groups. Because grouping is based on existing health status rather than random assignment, the results will focus on identifying meaningful trends and individual responses rather than establishing strict cause-and-effect relationships.

At the end of this study, it is expected that clearer information will be obtained on how a Mediterranean diet combined with different types of exercise affects blood sugar control in women with prediabetes. The findings may help improve personalized lifestyle strategies for preventing diabetes and maintaining healthy blood sugar levels.

• Change in Body Weight [Time frame: Baseline (Week 0), Weeks 2, 4, 6, 8, 10, and 12.]
• Change in Body Mass Index (BMI) [Time frame: Baseline (Week 0), Weeks 2, 4, 6, 8, 10, and 12.]
• Change in Body Fat Percentage [Time frame: Baseline (Week 0), Weeks 2, 4, 6, 8, 10, and 12.]
• Change in Waist-to-Hip Ratio [Time frame: Baseline (Week 0), Weeks 2, 4, 6, 8, 10, and 12.]
• Change in Glycemic Variability (CV) [Time frame: Exercise groups: Baseline (week 2) , Week 6, Week 10 and Week 13. Control group: Baseline (week 2) and Week 13.]
• Change in Continuous Glucose Monitoring (CGM)-Derived Time in Range (TIR) [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]
• Change in Continuous Glucose Monitoring (CGM)-Derived Time Above Range (TAR) [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]
• Change in Continuous Glucose Monitoring (CGM)-Derived Time Below Range (TBR) [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]
• Change in Mean Glucose [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]
• Change in Glucose Standard Deviation (SD) [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]
• Change in Coefficient of Variation (CV) [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]
• Change in Glucose Management Indicator (GMI) [Time frame: First 10 days of the intervention, Last 10 days of the cycling phase (Weeks 5-6), Last 10 days of the rowing phase (Weeks 9-10), Final 10 days of the intervention.]