title: No effect of short-term green tea extract supplementation on metabolism at rest or during exercise in the fed state.
abstract: Supplementation with green tea extract (GTE) in animals has been reported to induce numerous metabolic adaptations including increased fat oxidation during exercise and improved performance. However, data regarding the metabolic and physiological effects of GTE during exercise in humans are limited and equivocal.
  
  
  OBJECTIVE
  To examine the effects of short-term GTE treatment on resting energy expenditure (REE), wholebody substrate utilization during exercise and time trial performance.
  
  
  METHODS
  Fifteen active men (24 ± 3 y; VO(2)peak = 48 ± 7 ml · kg · min(-1); BMI = 26 ± 3 kg · m(2)((-1))) ingested GTE (3x per day = 1,000 mg/d) or placebo (PLA) for 2 day in a double-blind, crossover design (each separated by a 1 week wash-out period). REE was assessed in the fasted state. Subjects then ingested a standardized breakfast (~5.0 kcal · kg(-1)) and 90 min later performed a 60 min cycling bout at an intensity corresponding to individual maximal fat oxidation (44 ± 11% VO(2)peak), followed by a 250 kJ TT.
  
  
  RESULTS
  REE, whole-body oxygen consumption (VO2) and substrate oxidation rates during steady-state exercise were not different between treatments. However, mean heart rate (HR) was lower in GTE vs. PLA (115 ± 16 vs. 118 ± 17 beats · min(-1); main effect, p = .049). Mixed venous blood [glycerol] was higher during rest and exercise after GTE vs. PLA (p = .006, main effect for treatment) but glucose, insulin and free-fatty acids were not different. Subsequent time trial performance was not different between treatments (GTE = 25:38 ± 5:32 vs. PLA = 26:08 ± 8:13 min; p = .75).
  
  
  CONCLUSIONS
  GTE had minimal effects on whole-body substrate metabolism but significantly increased plasma glycerol and lowered heart rate during steady-state exercise, suggesting a potential increase in lipolysis and a cardiovascular effect that warrants further investigation.
authors.affiliation: Dept. of Kinesiology, McMaster University, Hamilton, Ontario, Canada.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Martin
authors.forename: Rachel B
authors.initials: RB
authors.lastname: Tan
authors.forename: Jenna B
authors.initials: JB
authors.lastname: Gillen
authors.forename: Michael E
authors.initials: ME
authors.lastname: Percival
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Gibala
mesh_terms: D000328:Adult; D001481:Basal Metabolism / Q000187:drug effects / Q000502:physiology; D028241:Camellia sinensis / Q000737:chemistry*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects*; D015444:Exercise / Q000502:physiology*; D005990:Glycerol / Q000097:blood; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008066:Lipolysis / Q000187:drug effects / Q000502:physiology; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D010101:Oxygen Consumption / Q000187:drug effects; D010936:Plant Extracts / Q000494:pharmacology*; D012146:Rest / Q000502:physiology*; D012527:Satiation; D013662:Tea / Q000737:chemistry*
chemical_list: D010936:Plant Extracts; D013662:Tea; D005990:Glycerol