Type 2 diabetes mellitus (T2DM) is a major global health problem with rapidly increasing prevalence. Prediabetes represents a high-risk state for developing T2DM and is often asymptomatic, delaying diagnosis and intervention. Early identification and effective lifestyle interventions are essential to prevent or delay the progression to diabetes. Primary care settings provide an important opportunity for screening and implementing preventive strategies.

Lifestyle modification, including dietary changes and physical activity, is the cornerstone of diabetes prevention. Carbohydrate counting is a medical nutrition therapy widely used in diabetes management and has been shown to improve glycemic control. However, there is limited evidence regarding its effectiveness in individuals with prediabetes.

This study aims to evaluate the effect of basic carbohydrate counting education on HbA1c levels in individuals with prediabetes in a primary care setting.

This randomized controlled trial will be conducted in the Family Medicine outpatient clinic of Marmara University Hospital. Individuals aged 18 years and older with HbA1c levels between 5.7% and 6.4% will be included. Participants will be randomized into intervention and control groups in a 2:1 ratio.

The control group will receive standard lifestyle recommendations, while the intervention group will receive additional structured basic carbohydrate counting education in three sessions. HbA1c levels will be measured at baseline,at third and at 6 months. Secondary outcomes include body weight, body mass index, waist circumference,lipid panel and carbohydarte counting knowledge scale The findings of this study are expected to contribute to the development of effective, scalable, and practical nutritional interventions for diabetes prevention in primary care

Type 2 diabetes mellitus (T2DM) is a major and rapidly growing global health problem. Prediabetes represents a high-risk state for progression to T2DM and provides a critical window for preventive interventions. Since prediabetes is often asymptomatic, early detection and effective lifestyle-based strategies are essential. Primary care settings offer an optimal environment for identifying high-risk individuals and implementing preventive interventions.

Lifestyle modification, particularly dietary interventions and physical activity, is the cornerstone of diabetes prevention. Medical nutrition therapy (MNT) has been shown to play a key role in improving glycemic outcomes. Basic carbohydrate counting (CC), as a component of MNT, is a practical and structured dietary approach aimed at increasing awareness of carbohydrate intake and improving glycemic control. However, evidence regarding its effectiveness in individuals with prediabetes remains limited.

This study aims to evaluate the effect of basic carbohydrate counting education on HbA1c levels in individuals with prediabetes in a primary care setting.

This study will be designed as a randomized controlled trial conducted at the Family Medicine outpatient clinic of Marmara University Hospital. Adults aged 18 years and older with HbA1c levels between 5.7% and 6.4% who meet the inclusion criteria and provide informed consent will be enrolled.

Participants will be randomized into intervention and control groups using a simple randomization method in a 2:1 ratio. All participants will receive standard lifestyle recommendations as part of usual care. Additionally, a booklet including information on healthy nutrition and basic carbohydrate counting, prepared based on current scientific literature, will be provided to all participants.

At baseline, all participants will complete a questionnaire assessing sociodemographic characteristics and diabetes-related factors. The "Nutrition and Basic Carbohydrate Counting Knowledge Scale" will be administered at baseline, 3 months, and 6 months. This scale consists of 20 items, including true/false statements and two fill-in-the-blank questions related to fasting and postprandial blood glucose.

Anthropometric measurements including body weight, body mass index (BMI), and waist circumference (WC) will be recorded at baseline, 3 months, and 6 months. Laboratory assessments including HbA1c, fasting blood glucose (FBG), and lipid profile will also be performed at the same time points.

Participants in the intervention group will receive structured basic carbohydrate counting education delivered in three sessions at one-week intervals, each lasting 30-45 minutes. The training program will be developed in collaboration with a dietitian. Participants in the intervention group will also be asked to complete 3-day dietary records before each training session.

Following the training sessions, participants in the intervention group will be followed up with monthly telephone calls. During these follow-ups, adherence to the intervention will be evaluated, and participants' questions will be addressed.

The primary outcome of the study will be the change in HbA1c levels from baseline to 6 months. Secondary outcomes will include changes in body weight, BMI, waist circumference, lipid profile, and carbohydrate counting knowledge level.

This study is expected to provide evidence on the effectiveness of a practical and applicable dietary intervention in preventing the progression from prediabetes to T2DM in primary care settings.

Inclusion Criteria:

• Adults aged 18 years and older
• Able to read and write Individuals with prediabetes who are not using or are unwilling to initiate oral antidiabetic drugs.

Exclusion Criteria:

• Individuals with a diagnosis of diabetes mellitus
• Those who have previously received carbohydrate counting training or are currently applying carbohydrate counting
• Individuals with low daily carbohydrate intake (<100 g/day)
• Presence of uncontrolled medical conditions that may affect dietary intake, as determined by the investigator
• Pregnant or breastfeeding women, or those planning pregnancy during the study period
• Participation in another clinical study Inability or unwillingness to provide informed consent or comply with study procedures
• Cognitive impairment or communication difficulties (hearing, understanding, or speaking)