Meal Frequency and Timing on Metabolic Health in Patients With Type 2 Diabetes

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.