Protein and Performance (PROPER) in Endurance Athletes
- Conditions
- Diet, HealthyProtein Deficiency
- Interventions
- Other: Dietary intervention of normal protein intakeOther: Dietary intervention of reduced protein intake
- Registration Number
- NCT05426447
- Lead Sponsor
- University of Copenhagen
- Brief Summary
The present study is a parallel group design with randomised allocation to either a 1) reduced protein diet (RP) or a 2) normal protein diet (NP). The two groups will be pair-matched based on habitual dietary protein intake, endurance training, endurance performance, and sex.
The aim of the study is to investigate the effects of reducing dietary protein (\~1g protein/kg body mass) compared to an eucaloric normal protein diet (\~2g protein/kg body mass) for 6 weeks in well-trained endurance athletes on endurance performance, body composition, skeletal muscle protein synthesis, and health-related outcomes.
The hypothesis is that endurance performance will maintain or even be improved in well-trained endurance athletes after a 6-week dietary intervention of an eucaloric, protein reduced diet compared to a normal protein rich diet.
- Detailed Description
Design: The present study will include two phases: a 3-week run-in period, and a 6-week intervention of controlled diets containing either a reduced dietary protein (RP) or normal (habitual) protein (NP). The run-in period serves as a period for obtaining general activity data and habitual dietary and training habits in order to match the groups before entering the dietary intervention period.
Subjects and dietary goals: The study is aiming at including 20 male endurance athletes exercising \~15hrs+/week. The 20 males will be pair-matched based on habitual endurance training, habitual dietary protein intake, and endurance performance, and allocated in a randomised order to: 1) a reduced-protein diet (RP) or 2) a normal-protein diet (NP).
3-weeks run-in period: After a minimum of 7 days after written consent has been obtained, the run-in period will begin. Habitual endurance training volumes will be registered in an online platform (TrainingPeaks) and daily activity level will be monitored using an accelerometer (SENS) throughout the run-in and diet intervention period. "Heavy water" (D2O) will be ingested in a large bolus (3.5ml/kg LBM) upon beginning of the run-in period and plasma enrichments will be maintained throughout the study period by ingesting small daily boluses. This serves to determine skeletal muscle protein synthesis throughout the study.
6-weeks dietary intervention: The diets will be eucaloric and the estimated energy percentages for macronutrients will be as follows: RP - Protein \~7E%, Carbohydrate \~63E%, Fat \~29E%. NP - Protein \~16E%, Carbohydrate \~53E%, Fat \~30E%. Weekly urine and faeces samples will be collected during the run-in period and dietary intervention and the controlled diets will be supplied weekly for the participants.
Testing: Extensive endurance performance and metabolic testing will be performed prior to-, and during the intervention on weeks -1, 0 (Pre), 3 (Mid), and 6 (Post). The tests include: Body composition by DXA-scanning, resting metabolic rate by online respirometry using a Vyntus (Jaeger, PCX), venous blood-, and skeletal muscle biopsy sampling from m. Vastus Lateralis, a standardised breakfasts, endurance cycling on an electro-magnetically braked bike (Lode Excalibur) or running on a motorised treadmill (Woodway), and haemoglobin mass measuring using a modified version of the CO-rebreathing method.
The body mass will be kept unchanged during the 6-weeks dietary intervention.
Recruitment & Eligibility
- Status
- ACTIVE_NOT_RECRUITING
- Sex
- Male
- Target Recruitment
- 20
- Endurance athlete
- Exercising at least 10hrs per week
- Habitual dietary protein intake ~2g/kg body mass
- BMI<25
- Food allergies that exclude the controlled diet
- Inconsistent endurance training load
Study & Design
- Study Type
- INTERVENTIONAL
- Study Design
- PARALLEL
- Arm && Interventions
Group Intervention Description Normal protein diet Dietary intervention of normal protein intake A 6-week eucaloric dietary intervention of normal protein intake (\~2g protein/kg body mass). The diet will, hence, contain \~16E% protein, \~53E% carbohydrate, and \~30E% fat. Participants are free-living and receive all food pre-packed from the study kitchen. The energy provision will be set to match energy balance. Reduced protein diet Dietary intervention of reduced protein intake A 6-week eucaloric dietary intervention of reduced protein intake (\~1g protein/kg body mass). The diet will, hence, contain \~7E% protein, \~63E% carbohydrate, and \~29E% fat. Participants are free-living and receive all food pre-packed from the study kitchen. The energy provision will be set to match energy balance.
- Primary Outcome Measures
Name Time Method Microbiome Run-in (week-3 to week0) vs dietary intervention (week0 to week6) Diversity of bacterial strains in gut microbiome measured in feces samples
Endurance performance on a bike From Pre (week0) to post (week6) Endurance performance defined as maximal aerobic power (Wmax) during incremental test to exhaustion on a bike measured as 1-minute mean power output (W)
- Secondary Outcome Measures
Name Time Method Total fat mass Run-in (week-3) to Pre (week0) Measured by dual-energy x-ray (DXA)-scanning expressed in kg
Training load Run-in (week-3) vs dietary intervention (week0 to week6) Training load as quantified by Edward's Training Impulse based on heart rate zones
Resting metabolic rate Pre (week0) to Post (week6) Measured in an over-night fasted state via indirect calorimetry expressed in MJ/day
Lean body mass Pre (week0) to Post (week6) Measured by dual-energy x-ray (DXA)-scanning expressed in kg
Fractional utilisation of maximal oxygen uptake at 4mmol/L blood lactate Pre (week0) to Post (week6) Alterations in Fractional utilisation of maximal oxygen uptake at 4mmol/L blood lactate in response to diet
Gross work efficiency on a bike Pre (week0) to Post (week6) Gross efficiency expressed as % of external power compared to internal (metabolic) power
Respiratory exchange ratio Pre (week0) to Mid (week3) respiratory exchange ratio (RER) during rest and exercise using indirect calorimetry
Energy intake Run-in (week-3) vs dietary intervention (week0 to week6) Habitual energy intake registered by food diaries expressed in Mega Joules
Power output at 4mmol/L blood lactate Pre (week0) to Post (week6) Alterations in Power output at 4mmol/L blood lactate in response to diet
Peak power output on a 10-seconds sprint Pre (week0) to Post (week6) Alterations in peak power output on a 10-seconds sprint in response to diet
Mean power output on a 10-seconds sprint Pre (week0) to Post (week6) Alterations in mean power output on a 10-seconds sprint in response to diet
Gross efficiency on a bike Pre (week0) to mid (week3) Gross efficiency expressed as % of external power compared to internal (metabolic) power
15-minute time-trial power output on a bike Pre (week0) to Post (week6) Alterations in 15-minute time-trial mean power output
Fractional utilisation of maximal oxygen uptake during 15-minute time-trial Pre (week0) to Post (week6) Alterations in Fractional utilisation of maximal oxygen uptake during 15-minute time-trial
Blood lactate concentration Run-in (week-3 to week0) vs dietary intervention (week0 to week6) Glucose lactate measured in fasted state on an ABL800
Plasma metabolomics Run-in (week-3 to week0) vs dietary intervention (week0 to week6) Plasma metabolomics by chromatography-mass spectrometry
Maximal oxygen uptake VO2peak Pre (week0) to Post (week6) Alterations in Maximal oxygen uptake VO2peak measured by an online VO2 apparatus
Energy expenditure Run-in (week-3) vs dietary intervention (week0 to week6) Energy expenditure is measured by combining resting metabolic rate and daily activity recording from accelerometer data and heart rate monitor
Blood glucose concentration Run-in (week-3 to week0) vs dietary intervention (week0 to week6) Glucose concentration measured in fasted state on an ABL800
Skeletal muscle protein expression Pre (week0) to Post (week6) Alterations in Skeletal muscle protein expression
Haemoglobin mass expressed in grams Pre (week0) to Post (week6) Haemoglobin mass measured via inhalation of carbon monoxide (CO) using the modified CO-rebreathing method
Blood amino acid concentration Run-in (week-3 to week0) vs dietary intervention (week0 to week6) Amino acid concentration measured by ELISA
Blood volume in ml Pre (week0) to Mid (week3) Blood volume measured via inhalation of carbon monoxide (CO) using the modified CO-rebreathing method
Energy expenditure measured as energy intake to maintain body weight Run-in (week-3 to week0) vs dietary intervention (week0 to week6) Daily energy intake during intervention measured in Mega Joules
Trial Locations
- Locations (1)
University of Copenhagen
🇩🇰Copenhagen, Denmark