title: Metabolic response to carbohydrate ingestion during exercise in males and females.
abstract: The present study investigated potential sex-related differences in the metabolic response to carbohydrate (CHO) ingestion during exercise. Moderately endurance-trained men and women (n = 8 for each sex) performed 2 h of cycling at approximately 67% Vo(2 max) with water (WAT) or CHO ingestion (1.5 g of glucose/min). Substrate oxidation and kinetics were quantified during exercise using indirect calorimetry and stable isotope techniques ([(13)C]glucose ingestion, [6,6-(2)H(2)]glucose, and [(2)H(5)]glycerol infusion). In both sexes, CHO ingestion significantly increased the rates of appearance (R(a)) and disappearance (R(d)) of glucose during exercise compared with WAT ingestion [males: WAT, approximately 28-29 micromol x kg lean body mass (LBM)(-1) x min(-1); CHO, approximately 53 micromol x kg LBM(-1) x min(-1); females: WAT, approximately 28-29 micromol x kg LBM(-1) x min(-1); CHO, approximately 61 micromol x kg LBM(-1) x min(-1); main effect of trial, P < 0.05]. The contribution of plasma glucose oxidation to the energy yield was significantly increased with CHO ingestion in both sexes (from approximately 10% to approximately 20% of energy expenditure; main effect of trial, P < 0.05). Liver-derived glucose oxidation was reduced, although the rate of muscle glycogen oxidation was unaffected with CHO ingestion (males: WAT, 108 +/- 12 micromol x kg LBM(-1) x min(-1); CHO, 108 +/- 11 micromol x kg LBM(-1) x min(-1); females: WAT, 89 +/- 10 micromol x kg LBM(-1) x min(-1); CHO, 93 +/- 11 micromol x kg LBM(-1) x min(-1)). CHO ingestion reduced fat oxidation and lipolytic rate (R(a) glycerol) to a similar extent in both sexes. Finally, ingested CHO was oxidized at similar rates in men and women during exercise (peak rates of 0.70 +/- 0.08 and 0.65 +/- 0.06 g/min, respectively). The present investigation suggests that the metabolic response to CHO ingestion during exercise is largely similar in men and women.
authors.affiliation: School of Sport and Exercise Sciences, University of Birmingham, UK.
authors.forename: Gareth A
authors.initials: GA
authors.lastname: Wallis
authors.forename: Ruth
authors.initials: R
authors.lastname: Dawson
authors.forename: Juul
authors.initials: J
authors.lastname: Achten
authors.forename: Jonathan
authors.initials: J
authors.lastname: Webber
authors.forename: Asker E
authors.initials: AE
authors.lastname: Jeukendrup
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000032:analysis; D002153:Calorimetry, Indirect; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005947:Glucose / Q000378:metabolism; D005990:Glycerol / Q000097:blood; D006801:Humans; D007328:Insulin / Q000097:blood; D019344:Lactic Acid / Q000097:blood; D008297:Male; D012737:Sex Factors
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D019344:Lactic Acid; D005947:Glucose; D005990:Glycerol