title: Gender differences in carbohydrate loading are related to energy intake.
abstract: We demonstrated that female endurance athletes did not increase their muscle glycogen concentration after an increase in the dietary carbohydrate intake (58 --> 74%), whereas men did (Tarnopolsky MA, SA Atkinson, SM Phillips, and JD McDougall, J Appl Physiol 78: 1360-1368, 1995). This may have been related to a lower energy or carbohydrate intake by the women or due to an inherent gender difference in glycogen storage capacity. We examined whether well-trained men (n = 6) and women (n = 6) increased muscle glycogen concentration after an increase in both the relative (58 --> 75%) and absolute energy and carbohydrate intake and whether potential gender differences were related to muscle hexokinase enzyme activity. Subjects were randomly allocated to three diets [Hab, habitual; CHO, high carbohydrate (75%); and CHO + E, extra energy + CHO ( upward arrow~34%)] for a 4-day period before a muscle biopsy for analysis of total and pro- and macroglycogen and hexokinase activity. Total glycogen concentration was higher for the men on the CHO and CHO + E trials compared with Hab (P < 0.05), whereas women increased only on the CHO + E trial compared with Hab (P < 0.05). There were no gender differences in the proportion of pro- and macroglycogen or hexokinase activity. A low energy intake may explain the previously reported lower capacity for women to glycogen load compared with men.
authors.affiliation: Departments of Medicine (Neurology and Rehabilitation), McMaster University, Hamilton, Ontario L8N 3Z5. tarnopol@mcmaster.ca
authors.forename: M A
authors.initials: MA
authors.lastname: Tarnopolsky
authors.forename: C
authors.initials: C
authors.lastname: Zawada
authors.forename: L B
authors.initials: LB
authors.lastname: Richmond
authors.forename: S
authors.initials: S
authors.lastname: Carter
authors.forename: J
authors.initials: J
authors.lastname: Shearer
authors.forename: T
authors.initials: T
authors.lastname: Graham
authors.forename: S M
authors.initials: SM
authors.lastname: Phillips
mesh_terms: D000328:Adult; D004032:Diet; D004040:Dietary Carbohydrates / Q000008:administration & dosage*; D004311:Double-Blind Method; D002149:Energy Intake; D005260:Female; D006003:Glycogen / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism; D006801:Humans; D008297:Male; D018482:Muscle, Skeletal / Q000201:enzymology; D012727:Sex Characteristics
chemical_list: D004040:Dietary Carbohydrates; D006003:Glycogen; D006593:Hexokinase