title: High protein diet maintains glucose production during exercise-induced energy deficit: a controlled trial.
abstract: BACKGROUND
  Inadequate energy intake induces changes in endogenous glucose production (GP) to preserve muscle mass. Whether addition provision of dietary protein modulates GP response to energy deficit is unclear. The objective was to determine whether exercise-induced energy deficit effects on glucose metabolism are mitigated by increased dietary protein.
  
  
  METHODS
  Nineteen men ([mean ± SD] 23 ± 2 y, VO2peak 59 ± 5 ml·kg-1·min-1) were divided into three groups, two consuming moderate (MP; 0.9 g protein kg-1 d-1), and one high (HP; 1.8 g protein kg-1 d-1) protein diets (55% energy from carbohydrate) for 11 days. Following 4 days of energy balance (D1-4), energy expenditure was increased for 7 days (D5-12) in all groups. Energy intake was unchanged in two, creating a 1000 kcal d-1 deficit (DEF-MP, DEF-HP; n = 6, both groups), whereas energy balance was maintained in the third (BAL-MP, n = 7). Biochemical markers of substrate metabolism were measured during fasting rest on D4 and D12, as were GP and contribution of gluconeogenesis to endogenous glucose production (fgng) using 4-h primed, continuous infusions of [6,6-2H2]glucose (dilution-method) and [2-13C]glycerol (MIDA technique). Glycogen breakdown (GB) was derived from GP and fgng.
  
  
  RESULTS
  Plasma β-hydroxybutyrate levels increased, and plasma glucose and insulin declined from D4 to D12, regardless of group. DEF-MP experienced decreased plasma GP from D4 to D12 ([mean change ± SD] 0.24 ± 0.24 mg·kg-1·min-1), due to reduced GB from D4 (1.40 ± 0.28 mg·kg-1·min-1) to D12 (1.16 ± 0.17 mg·kg-1·min-1), P < 0.05. Conversely, BAL-MP and DEF-HP sustained GP from D4 to D12 ([mean change ± SD] 0.1 ± 0.5 and 0.0 ± 0.2 mg·kg-1·min-1, respectively) by maintaining GB.
  
  
  CONCLUSIONS
  Exercise-induced energy deficit decreased GP and additional dietary protein mitigated that effect.
authors.affiliation: U,S, Army Research Institute of Environmental Medicine, Military Nutrition Division, Kansas Street, Building 42, Natick, MA 01760, USA. tracey.j.smith@us.army.mil.
authors.forename: Tracey J
authors.initials: TJ
authors.lastname: Smith
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Schwarz
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Montain
authors.forename: Jennifer
authors.initials: J
authors.lastname: Rood
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Pikosky
authors.forename: Carmen
authors.initials: C
authors.lastname: Castaneda-Sceppa
authors.forename: Ellen
authors.initials: E
authors.lastname: Glickman
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Young