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

NCT07438158 | Not Yet Recruiting

• 1 other identifier: 0011980-1
• Study Type: interventional
• Target: 69
• Locations: 0 countries
• Sites: N/A

Brief Summary

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.

Conditions

Muscle Damage

Keywords

Tactical Athletes; Protein Distribution; Leucine Supplementation; Lean Body Mass; Muscle Protein Synthesis; Resistance Training

Outcome Measures

Primary Outcomes (1)

• Change in Lean Body Mass (LBM)

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

  Baseline (Week 1) to Week 8

Secondary Outcomes (17)

• Change in Fat Mass Percentage

  Baseline (Week 1), Week 5, and Week 8

• Change in Fat-Free Mass (FFM)

  Baseline (Week 1), Week 5, and Week 8

• Change in Skeletal Muscle Mass (SMM)

  Baseline (Week 1), Week 5, and Week 8

• Change in Maximal Strength - Isometric Mid-Thigh Pull (IMTP)

  Baseline (Week 1), Week 5, and Week 8

• Change in Maximal Voluntary Isometric Contraction (MVC)

  Baseline (Week 1), Week 5, and Week 8

Study Arms (3)

EVEN (Even Protein Distribution)

OTHER

Participants consume an iso-caloric diet providing 1.6 g/kg/day protein, distributed evenly across three daily meals at approximately 08:00, 13:00, and 18:00, with each meal providing \~one-third of daily protein. Participants follow an overnight protein fasting window of approximately 21:00-08:00.

Behavioral: Even Protein Distribution

FAST (Protein-Fasting Morning; Protein at Lunch + Dinner)

EXPERIMENTAL

Participants consume an iso-caloric diet providing 1.6 g/kg/day protein using a skewed distribution that creates a 16-hour protein-free window (21:00-13:00) by omitting protein at breakfast (breakfast contains carbohydrate and fat only). Daily protein intake is concentrated at lunch and dinner to achieve the total 1.6 g/kg/day target.

Behavioral: Skewed Protein Distribution (16-hour Protein-Fasting Window)

FAST-RESCUE (FAST + Leucine at Breakfast)

EXPERIMENTAL

Identical dietary pattern to FAST: iso-caloric diet with 1.6 g/kg/day protein, protein-free breakfast, and protein concentrated at lunch and dinner, creating a 16-hour protein-free window (21:00-13:00).

Dietary Supplement: L-leucine supplementation

Interventions

L-leucine supplementation DIETARY_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.

FAST-RESCUE (FAST + Leucine at Breakfast)

Even Protein Distribution BEHAVIORAL

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

EVEN (Even Protein Distribution)

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.

FAST (Protein-Fasting Morning; Protein at Lunch + Dinner)

Eligibility Criteria

• Age: 18 Years - 35 Years
• Sex: male
• Healthy Volunteers: Yes
• Age Groups: Adult (18-64)

You may qualify if:

• 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

You may not qualify if:

• 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

Sponsors & Collaborators

• Tel Aviv University: lead

Study Officials

• Yftach Gepner, PhD

  Tel Aviv University

  PRINCIPAL INVESTIGATOR

Central Study Contacts

Lien Bruck

CONTACT

0587487431; lien.brueck@gmail.com

Lien Bruck

CONTACT

0587487431; lien.bruck@tauex.tau.ac.il

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Masking Details: Due to the nature of the dietary intervention and differences in meal timing, participants and study personnel responsible for dietary supervision are not blinded to group allocation. Laboratory analyses of biochemical outcomes may be performed without knowledge of group assignment.
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Principal Investigator - Professor

Model Details: This is a three-arm, parallel-group randomized controlled trial. Participants will be randomly assigned in a 1:1:1 ratio to one of three dietary intervention groups (EVEN, FAST, FAST-RESCUE) for 8 weeks during an intensive tactical training program. Each group will follow a distinct protein distribution strategy while maintaining identical total daily protein intake (1.6 g/kg/day) and iso-caloric energy intake.

Study Record Dates

• First Submitted: February 22, 2026
• First Posted: February 27, 2026
• Study Start: March 1, 2026
• Primary Completion (Estimated): December 1, 2028
• Study Completion (Estimated): December 1, 2028
• Last Updated: March 2, 2026

Record last verified: 2026-02

Data Sharing

• IPD Sharing: Will not share