title: Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial.
abstract: BACKGROUND
  A dietary protein intake higher than the Recommended Dietary Allowance during an energy deficit helps to preserve lean body mass (LBM), particularly when combined with exercise.
  
  
  OBJECTIVE
  The purpose of this study was to conduct a proof-of-principle trial to test whether manipulation of dietary protein intake during a marked energy deficit in addition to intense exercise training would affect changes in body composition.
  
  
  METHODS
  We used a single-blind, randomized, parallel-group prospective trial. During a 4-wk period, we provided hypoenergetic (~40% reduction compared with requirements) diets providing 33 ± 1 kcal/kg LBM to young men who were randomly assigned (n = 20/group) to consume either a lower-protein (1.2 g · kg(-1) · d(-1)) control diet (CON) or a higher-protein (2.4 g · kg(-1) · d(-1)) diet (PRO). All subjects performed resistance exercise training combined with high-intensity interval training for 6 d/wk. A 4-compartment model assessment of body composition was made pre- and postintervention.
  
  
  RESULTS
  As a result of the intervention, LBM increased (P < 0.05) in the PRO group (1.2 ± 1.0 kg) and to a greater extent (P < 0.05) compared with the CON group (0.1 ± 1.0 kg). The PRO group had a greater loss of fat mass than did the CON group (PRO: -4.8 ± 1.6 kg; CON: -3.5 ± 1.4kg; P < 0.05). All measures of exercise performance improved similarly in the PRO and CON groups as a result of the intervention with no effect of protein supplementation. Changes in serum cortisol during the intervention were associated with changes in body fat (r = 0.39, P = 0.01) and LBM (r = -0.34, P = 0.03).
  
  
  CONCLUSIONS
  Our results showed that, during a marked energy deficit, consumption of a diet containing 2.4 g protein · kg(-1) · d(-1) was more effective than consumption of a diet containing 1.2 g protein · kg(-1) · d(-1) in promoting increases in LBM and losses of fat mass when combined with a high volume of resistance and anaerobic exercise. Changes in serum cortisol were associated with changes in body fat and LBM, but did not explain much variance in either measure. This trial was registered at clinicaltrials.gov as NCT01776359.
authors.affiliation: Department of Kinesiology, Exercise Metabolism Research Group, McMaster University, Hamilton, Canada.
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Longland
authors.affiliation: Department of Kinesiology, Exercise Metabolism Research Group, McMaster University, Hamilton, Canada.
authors.forename: Sara Y
authors.initials: SY
authors.lastname: Oikawa
authors.affiliation: Department of Kinesiology, Exercise Metabolism Research Group, McMaster University, Hamilton, Canada.
authors.forename: Cameron J
authors.initials: CJ
authors.lastname: Mitchell
authors.affiliation: Department of Kinesiology, Exercise Metabolism Research Group, McMaster University, Hamilton, Canada.
authors.forename: Michaela C
authors.initials: MC
authors.lastname: Devries
authors.affiliation: Department of Kinesiology, Exercise Metabolism Research Group, McMaster University, Hamilton, Canada phillis@mcmaster.ca.
authors.forename: Stuart M
authors.identifier: http://orcid.org/0000-0002-1956-4098
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D000273:Adipose Tissue / Q000378:metabolism*; D000328:Adult; D001823:Body Composition; D001825:Body Fluid Compartments / Q000378:metabolism*; D031204:Caloric Restriction; D004032:Diet; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000494:pharmacology; D002149:Energy Intake; D015444:Exercise; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D008297:Male; D009751:Nutritional Requirements; D005082:Physical Exertion; D011446:Prospective Studies; D055070:Resistance Training; D016037:Single-Blind Method; D055815:Young Adult
chemical_list: D004044:Dietary Proteins; D006854:Hydrocortisone
keywords: athlete; dietary protein; high-intensity interval training; leucine; resistance exercise; skeletal muscle