title: Dietary macronutrient distribution influences postexercise substrate utilization in women: a cross-sectional evaluation of metabolic flexibility.
abstract: BACKGROUND
  Metabolic flexibility is the ability to alter substrate utilization in response to substrate availability, which may influence health and performance. The current study evaluated the effects of habitual macronutrient distribution on energy expenditure (EE) and metabolic flexibility in physically active women.
  
  
  METHODS
  Participants (N.=20) completed a 3-day food log and a standardized bout of high-intensity interval training to determine EE and respiratory exchange ratio (RER). EE and RER were measured via indirect calorimetry at rest (PRE) and immediately (IP), 30 minutes (30 min), and 60 minutes postexercise (60 min). To evaluate metabolic flexibility, RER changes were calculated from PRE to IP, IP to 30 min, and IP to 60 min. For each macronutrient, participants were categorized into high- and low-intake groups using a median split.
  
  
  RESULTS
  No significant correlations were observed between macronutrient distribution and EE when covaried for lean mass (all P≥0.232), and ANCOVAs revealed no significant group × time interactions (all P≥0.241). Fat intake was not associated with ∆RER (all P≥0.477). Correlations between PRO intake and ∆RER approached significance (r=0.373-0.411; P=0.079-0.115), as did inverse associations between CHO and ∆RER (r=-0.404 - -0.409; P=0.084-0.087). Lower RER values were observed in the low-CHO group at 30 min and 60 min (P=0.030) compared to high-CHO. Higher RER values were observed in the high-PRO group at IP (P=0.042) compared to low-PRO. Estradiol was not correlated with RER at any time point, or different between diet groups (all P≥0.401).
  
  
  CONCLUSIONS
  Results suggest that high PRO and low CHO intakes are associated with greater metabolic flexibility in women.
authors.affiliation: Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA.|Human Movement Science Curriculum, Department of Allied Health Sciences, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Eric T
authors.initials: ET
authors.lastname: Trexler
authors.affiliation: Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA - abbsmith@email.unc.edu.|Human Movement Science Curriculum, Department of Allied Health Sciences, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Abbie E
authors.initials: AE
authors.lastname: Smith-Ryan
authors.affiliation: Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Hailee L
authors.initials: HL
authors.lastname: Wingfield
authors.affiliation: Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Malia N
authors.initials: MN
authors.lastname: Blue
authors.affiliation: Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Erica J
authors.initials: EJ
authors.lastname: Roelofs
authors.affiliation: Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC, USA.
authors.forename: Katie R
authors.initials: KR
authors.lastname: Hirsch
mesh_terms: D000328:Adult; D002153:Calorimetry, Indirect; D003430:Cross-Sectional Studies; D004032:Diet; D019587:Dietary Supplements; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise; D005260:Female; D006801:Humans; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D055815:Young Adult