Protein Distribution and Leucine Supplementation Effects on Body Composition and Performance in Tactical Athletes

N/ANot Yet RecruitingNCT07438158

Tel Aviv University69 enrolled

Overview

This randomized controlled trial will examine the effects of within-day protein distribution and leucine supplementation on body composition, physical performance, and biomarkers of muscle damage in tactical athletes during an 8-week intensive training program. Sixty-nine healthy male participants (18-35 years) enrolled in a Ministry of Defense training course will be randomly assigned to one of three iso-caloric dietary groups providing 1.6 g/kg/day of protein: (1) evenly distributed protein across three meals (EVEN), (2) a 16-hour daily protein fasting pattern with protein concentrated at lunch and dinner (FAST), or (3) the same fasting pattern with 5 g leucine supplementation at breakfast (FAST-RESCUE). Primary outcomes include changes in lean body mass. Secondary outcomes include strength, anaerobic performance, and biochemical markers of muscle damage, including urinary titin N-terminal fragment (UTF). Assessments will be conducted at baseline, Week 5, and Week 8.

This study is an 8-week, three-arm, parallel-group randomized controlled trial conducted in healthy male tactical trainees (18-35 years) enrolled in a Ministry of Defense training program. Participants will undergo a high-volume concurrent training regimen exceeding 30 hours per week, including resistance training, load carriage, aerobic conditioning, and combat-based drills. Participants (n=69) will be randomized in a 1:1:1 ratio to one of three iso-caloric dietary interventions providing 1.6 g/kg/day of protein: 1. EVEN: Protein evenly distributed across three daily meals (08:00, 13:00, 18:00). 2. FAST: Skewed protein distribution with a 16-hour protein-free window (21:00-13:00), omitting protein at breakfast and concentrating intake at lunch and dinner. 3. FAST-RESCUE: Identical to FAST, with addition of 5 g free-form leucine consumed at breakfast. Energy intake will be individualized based on measured resting metabolic rate and estimated physical activity level. Dietary adherence will be monitored daily using a mobile application and weekly dietitian supervision. Primary Outcome: \- Change in lean body mass measured by bioelectrical impedance analysis from baseline to Week 8. Secondary Outcomes: * Maximal strength (isometric mid-thigh pull, maximal voluntary contraction, handgrip strength) * Anaerobic performance (Wingate test, countermovement jump) * Serum biomarkers (creatine kinase, urea, testosterone, inflammatory markers) * Urinary titin N-terminal fragment to creatinine ratio (UTF/Cr) as a marker of myofibrillar damage Assessments will be performed at baseline, Week 5, and Week 8. Data will be analyzed according to the intention-to-treat principle using linear mixed models to evaluate Group × Time interactions.

Interventions

L-leucine supplementationDIETARY_SUPPLEMENT

Participants ingest 5 g free-form L-leucine at breakfast (\~08:00) daily for 8 weeks. Leucine is provided as unflavored, pharmaceutical-grade instantized powder, reconstituted in water and consumed at the protein-free breakfast meal.

Even Protein DistributionBEHAVIORAL

Iso-caloric diet providing 1.6 g/kg/day protein evenly distributed across three daily meals for 8 weeks.

Skewed Protein Distribution (16-hour Protein-Fasting Window)BEHAVIORAL

Iso-caloric diet providing 1.6 g/kg/day protein with protein omitted at breakfast and concentrated at lunch and dinner, creating a 16-hour daily protein-free window for 8 weeks.

Eligibility

Sex: MALEMin age: 18 YearsMax age: 35 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * Male participants aged 18-35 years * Enrolled in an active Ministry of Defense tactical training program * Physically active and medically cleared to participate in intensive training * Willing and able to comply with the dietary intervention and training protocol * Provide written informed consent prior to participation Exclusion Criteria: * Musculoskeletal or neuromuscular injury or impairment limiting participation in exercise training * Cardiopulmonary disease (including recent myocardial infarction or unstable angina) * History of cancer, diabetes, thyroid disease, hypertension, or chronic renal failure * Cognitive impairment affecting ability to provide informed consent * Use of medications that may affect metabolism, muscle physiology, or exercise performance * Known allergy or intolerance to study dietary components or leucine supplementation * Non-compliance with study protocol requirements

Outcomes

Primary Outcomes

Change in Lean Body Mass (LBM)

Lean body mass (kg) assessed by multi-frequency bioelectrical impedance analysis (BIA) using the SECA mBCA 515.

Time frame: Baseline (Week 1) to Week 8

Secondary Outcomes

Change in Fat Mass Percentage

Fat mass percentage (%) assessed by multi-frequency bioelectrical impedance analysis (SECA mBCA 515).