The Impact of a High-protein Diet on Energy Metabolism in Healthy Men
Condition: Dietary Modification
Study type: Interventional

Summary: 
      The aim of this study is to investigate the impact of a high-protein diet (achieved with the
      use of a nutritional supplement, Almased®) versus a diet of a typical North American
      macronutrient distribution on energy metabolism, metabolic blood markers and appetite
      sensations.

      This study will be a randomized, controlled, cross-over trial of an acute nutritional
      intervention. A total of 20 participants will be randomly assigned (1:1) to one of the
      following groups:

        -  Control group (CON).

        -  High protein diet group (HP).

      The diets given to participants in both groups will be eucaloric.

      While receiving the diets in the whole body calorimetry unit for 32 hours, participants'
      overall changes in energy metabolism, metabolic blood markers, and appetite sensations will
      be assessed.
    

Detailed description: 
      This study will be a randomized, controlled, cross-over trial of an acute nutritional
      intervention. The participants will be randomly assigned (1:1) to one of the following
      groups:

        -  Control group (CON). Those assigned to the CON will receive a diet composed of 55% of
           carbohydrate, 15% of protein, and 30% of lipid (similar to the North American dietary
           pattern [3]).

        -  High protein diet group (HP). Those assigned to the HP will receive a diet composed of
           35% of carbohydrate, 40% of protein, and 25% of lipid constructed around a soy
           protein-based meal replacement (Almased®).

      The diets given to participants in both groups will be eucaloric.

      The following metabolic changes will be assessed between the diets:

        -  Energy metabolism (energy expenditure and substrate oxidation);

        -  Metabolic blood markers [glucose, insulin, lipid panel, peptide tyrosine-tyrosine (PYY),
           glucagon-like peptide-1 (GLP-1), ghrelin, leptin, free glycerol, and free fatty acids];

        -  Appetite sensations (hunger, satiety, fullness, and prospective food consumption).

      Sample Size: A total of 18 participants will be able to detect an effect size of 1.41. The
      effect size was calculated based on changes in RQ (0.90 ± 0.04 in control group and 0.85 ±
      0.03 in a high protein group) from a previously published study. Accounting for a 20%
      attrition rate (formula N=18/1-20%), the total sample size of 23 participants will have a
      power of 80% with a significance level of 5%. The sample size calculation was done using
      G*Power version 3.1.9.2.

      Visit # 1 - Screening Visit: During the screening visit, the study coordinator will run
      through the study protocol and obtain written informed consent as well as participants'
      contact information. Eligibility to participate in the study will be based on set inclusion
      and exclusion criteria, completion of physical activity questionnaires, anthropometric
      assessment, bioelectrical impedance analysis (BIA), and analysis of biomarkers for kidney and
      liver function, electrolyte status, and thyroid-stimulating hormone.

      Visit # 2 - Orientation Visit: During the orientation visit, participants will answer
      questions related to their health status and food preferences, will have their energy
      requirements assessed by an 1-hour WBCU test and will be provided an explanation about the
      run-in diet period. Body composition will also be assessed using dual energy X-ray
      absorptiometry (DXA) and air displacement plethysmography (ADP).

      Visits # 3 & 5 - Fitness Test & Run-In Diet Visit: To standardize the exercise intensity
      while in the WBCU, participants will attend a fitness test visit prior to their first WBCU
      test visit. They will perform a submaximal exercise test on a treadmill (Freemotion Incline
      Trainer). The exercise test will begin at an individualized walking speed characterized as
      comfortable and sustainable. The incline will increase by 2% every three minutes until a RER
      of 0.9 has been achieved. During exercise, expired gases will be analyzed by a calibrated
      TrueMax® metabolic measurement system (ParvoMedics, Sandy, UT). To reproduce the same
      conditions during the WBCU exercise session, a breakfast identical to that provided inside
      the WBCU (CON Group) will be given to participants at 9 am and the treadmill test will start
      at 10:20 am. To determine the workload for the WBCU exercise session, each participant's
      respiratory exchange ratio (RER) will be plotted against their fitness test workload. The
      workload at which an RER of 0.85 occurred will be selected as the workload for the WBCU. We
      anticipate there will be a RER of 0.85 ± 0.03 during the WBCU control exercise session. The
      small difference may be due to factors such as the change in substrate oxidation throughout a
      40-minute bout of exercise.

      After the fitness test, participants will receive all the meals necessary to complete the
      3-day run-in diet. This will standardize dietary intake among participants and minimize the
      effects of any eating style/behaviours on baseline data. The run-in diet will be a eucaloric
      diet and will have the same macronutrient distribution as of CON group diet (55% of
      carbohydrate, 15% of protein, and 30% of lipid). During this three-day run-in diet period,
      participants will be asked to abstain from any strenuous exercise, including endurance and/or
      resistance exercises. They can exercise (moderate) and drink coffee during the first and
      second days of run-in diet, but not during the third day.

      Visits # 4 & 6 - Whole Body Calorimetry Test Visits: Participants will complete a WBCU test
      visit twice during the study period, which will occur after the run-in diet periods. These
      visits will consist of two 32 hours (1.5 days) energy expenditure assessments inside the
      WBCU. During the 32-hour measurement period, participants of both groups (CON and HP) will be
      provided with a five-meal diet (breakfast, lunch, dinner, and two snacks) through an air-lock
      drawer system. The CON group will receive a diet composed of 55% of carbohydrate, 15% of
      protein, and 30% of lipid. The participants will receive breakfast, lunch, dinner and two
      snacks (afternoon and evening). The HP group will receive a diet composed of 35% of
      carbohydrate, 40% of protein, and 25% of lipid constructed around a soy protein-based meal
      replacement (Almased®). Participants will consume approximately 1 gram of Almased® per kg of
      body weight mixed with olive oil and low-fat milk (1% fat) in their breakfast, lunch and
      dinner. Two snacks (afternoon and evening) composed of approximately 1 gram of Almased® per
      kg of body weight mixed with apple juice and olive oil will also be provided. Amounts of
      low-fat milk, olive oil, and apple juice will be adjusted on an individual basis in order to
      achieve the desired macronutrient composition for the HP group. A variation of ± 2% for each
      macronutrient and ± 50 kcal/day will be considered.

      The exercise session will be performed on the first morning (from 10:20 a.m. to 11:00 a.m.)
      spent in the WBCU. The session will be performed on a treadmill (BH T10 Pro Treadmill). The
      speed and grade of the treadmill will be set based on the fitness test as previously
      described.

      Blood samples will be taken four times while participants are in the WBCU:

        -  Fasting on the first day (at 07:45 a.m.);

        -  After the exercise session on the first day (at 11:00 a.m.);

        -  Two hours postprandial on the first day (at 02:30 p.m.);

        -  Fasting on the second day (at 08:30 a.m.). The following blood markers will be analysed:
           glucose, insulin, lipid panel, PYY, GLP-1, ghrelin, leptin, free glycerol, and
           free-fatty acid. While participants are inside the WBCU, urine must be collected during
           the entire time. This is necessary to determine total nitrogen excretion, protein used
           by participant's body during the test day. Participants will be asked to rate their
           appetite sensations on a 100-mm visual analogue scale (VAS) immediately before and 30
           minutes after each meal and snack provided in the WBCU in order to measure subjective
           appetite sensations (hunger, satiety, fullness, and prospective food consumption).
           Participants will be asked to wear an accelerometer around the wrist during sleep. The
           motion sensor will measure participants' activity patterns during sleep. A two week
           wash-out period between the WBCU test visits is needed to reduce the carryover effects
           of the interventions. A two week washout period is typical of feeding trials with soy
           isoflavone intervention [4, 5].

      Statistical Analyses: Data distributions will be evaluated by the Shapiro-Wilk W-test.
      Parametric variables will be expressed in average and standard deviation and then converted
      into delta scores (i.e. post-pre values). To determine the differences among the variables
      analyzed after the intervention (within) and between CON and HP groups (between), Student's
      t-test or Mann-Whitney tests will be applied, according to data distribution. Pearson's
      correlation coefficients will be determined to assess whether there is a statistically
      significant correlation among the variables. All analyses will be performed using SPSS
      version 22.0, considering a critical significance value of 5%.
    

Intervention name(s): High-Protein Diet
Intervention type(s): Dietary Supplement
Intervention description(s): The high-protein diet is composed of 35% of carbohydrate, 40% of protein, and 25% of lipid constructed around a soy protein-based meal replacement.
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: High-protein diet; Energy metabolism