The goal of this clinical trial is to learn if changing when and how often people eat works to improve health in adults with Type 2 diabetes. The main questions it aims to answer are:

How do these eating patterns change body weight and body fat?

Does changing meal timing and frequency lower blood sugar levels (HbA1c) over 12 weeks?

Does it lower blood fat levels, such as cholesterol and triglycerides?

Researchers will compare three groups to see which eating pattern works best:

Standard Group: Participants eat 3 main meals and 3 snacks (6 times total) each day with a calorie limit.

3-Meal Group: Participants eat only 3 main meals each day with a calorie limit.

Time-Restricted Group: Participants eat all their daily food within an 8-hour window (from 12:00 to 20:00) without a calorie limit.

Participants will:

Follow their assigned eating plan for 12 weeks.

Visit the clinic once every month for checkups and body measurements.

Give blood samples at the start and end of the study for laboratory tests.

Record the food they eat and their physical activity levels.

This randomized controlled trial investigates the impact of meal frequency and timing on the body composition and metabolic profile of individuals diagnosed with Type 2 Diabetes Mellitus (T2DM). While medical management is a cornerstone of T2DM treatment, dietary patterns, specifically the distribution of meals and fasting windows, may significantly modulate glycemic variability and lipid metabolism.

Methodology and Rationale:

The study follows a three-arm parallel design for 12 weeks. Participants are randomized into Control (6 meals), 3-Meal, or Time-Restricted Eating (TRE) groups using Random Allocation Software.

Energy Expenditure Calculation: For the Control and 3-Meal groups, daily energy requirements are calculated using the Mifflin-St Jeor equation. A 500 kcal/day deficit is applied, ensuring that total energy intake does not fall below the Basal Metabolic Rate (BMR).

Time-Restricted Eating (TRE) Protocol: The TRE group follows an 8-hour eating window (12:00-20:00) consisting of 2 main meals and 2 snacks. Unlike the other groups, no explicit calorie restriction is mandated for the TRE arm, allowing the researchers to observe the spontaneous effects of a restricted feeding window on metabolic parameters.

Dietary Composition: All groups are instructed to follow standard medical nutrition therapy for T2DM, emphasizing high fiber, low saturated fat, and high-quality protein sources.

Sample Size and Statistical Power:

Sample size was estimated based on body weight changes reported in a 12-week time-restricted feeding RCT in overweight adults with type 2 diabetes (Che et al., 2021), which yielded a Cohen's f of 0.40 for between-group differences in body weight. Using one-way ANOVA with α = 0.05 and 80% power (G*Power 3.1), a minimum of 22 participants per group was required for the primary outcome. To also achieve adequate power for the secondary outcome of HbA1c (Cohen's f = 0.35, derived from the same reference), a minimum of 29 participants per group was indicated. Accounting for an anticipated 20% dropout rate, 48 participants per group (144 total) were enrolled

Data Collection and Follow-up:

Anthropometry: Body composition is analyzed monthly using Bioelectrical Impedance Analysis (BIA - Tanita MC 580).

Biochemistry: HbA1c, Fasting Plasma Glucose, Lipid Profile (Total-C, LDL-C, HDL-C, Triglycerides), and Albumin/Creatinine Ratio (UACR) are recorded at baseline and at the end of the 12th week.

Dietary Compliance: Weekly phone calls are conducted to monitor adherence, meal skipping, and protocol deviations. 24-hour dietary recalls are collected at baseline and at the 12th week to verify nutrient intake using professional nutrition software (BeBİS 9.0).

Inclusion Criteria:

• Diagnosed with Type 2 Diabetes Mellitus (T2DM) for at least 6 months.
• Aged between 18 and 65 years.
• Residing in Antalya, Turkey (to ensure regular follow-up visits).
• Able and willing to provide informed consent.
• Willing to comply with the assigned dietary protocol and follow-up measurements for 12 weeks.

Exclusion Criteria:

• Diagnosis of Type 1 Diabetes Mellitus or other specific types of diabetes.
• Current pregnancy or breastfeeding.
• Working in night shifts or irregular schedules (due to interference with Time-Restricted Eating protocols).
• Having a history of major cardiovascular events (e.g., myocardial infarction, stroke) within the last 6 months.
• Severe renal or hepatic impairment (e.g., Stage 4 or 5 Chronic Kidney Disease).
• Active malignancy or other chronic diseases that may significantly affect nutritional status.
• Significant weight change (more than 5% of body weight) within the last 3 months prior to the study.
• Use of medications that may significantly affect body weight or metabolism other than standard diabetes medications (e.g., systemic corticosteroids).
• History of major gastrointestinal surgery that affects nutrient absorption.
• Severe psychiatric disorders that may limit the ability to follow the study instructions.

Individual participant data collected during the trial, including biochemical and anthropometric measurements, will not be shared publicly to maintain participant confidentiality and adhere to the Personal Data Protection Law. The data are strictly confidential and belong to the primary research institution. Results will be disseminated through peer-reviewed publications and conference presentations in aggregate form.