title: Day to day variability in fat oxidation and the effect after only 1 day of change in diet composition.
abstract: Indirect calorimetry is a common and noninvasive method to estimate rate of fat oxidation (FatOx) during exercise, and test-retest reliability should be considered when interpreting results. Diet also has an impact on FatOx. The aim of the present study was to investigate day to day variations in FatOx during moderate exercise given the same diet and 2 different isoenergetic diets. Nine healthy, moderately-trained females participated in the study. They performed 1 maximal oxygen uptake test and 4 FatOx tests. Habitual diets were recorded and repeated to assess day to day variability in FatOx. FatOx was also measured after 1 day of fat-rich (26.8% carbohydrates (CHO), 23.2% protein, 47.1% fat) and 1 day of CHO-rich diet (62.6% CHO, 20.1% protein, 12.4% fat). The reliability test revealed no differences in FatOx, respiratory exchange ratio (RER), oxygen uptake, carbon dioxide production, heart rate, blood lactate concentration, or blood glucose between the 2 habitual diet days. FatOx decreased after the CHO-rich diet compared with the habitual day 2 (from 0.42 ± 0.15 to 0.29 ± 0.13 g·min(-1), p < 0.05). No difference was found in FatOx between fat-rich diet and the 2 habitual diet days. FatOx was 31% lower (from 0.42 ± 0.14 to 0.29 ± 0.13 g·min(-1), p < 0.01) after the CHO-rich diet compared with the fat-rich diet. Using RER data to measure FatOx is a reliable method as long as the diet is strictly controlled. However, even a 1-day change in macronutrient composition will likely affect the FatOx results.
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Eva Maria
authors.initials: EM
authors.lastname: Støa
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Lill-Katrin
authors.initials: LK
authors.lastname: Nyhus
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Sandra Claveau
authors.initials: SC
authors.lastname: Børresen
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Caroline
authors.initials: C
authors.lastname: Nygaard
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Åse Marie
authors.initials: ÅM
authors.lastname: Hovet
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Solfrid
authors.initials: S
authors.lastname: Bratland-Sanda
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.|b Norwegian University of Science and Technology, Faculty of Medicine, Department of Circulation and Medical Imaging, Trondheim, Norway.|c Hokksund Medical Rehabilitation Center, Hokksund, Norway.
authors.forename: Jan
authors.initials: J
authors.lastname: Helgerud
authors.affiliation: a Department of Sport and Outdoor Life Studies, Telemark University College, Bø, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Støren
mesh_terms: D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D015992:Body Mass Index; D002245:Carbon Dioxide / Q000378:metabolism; D004032:Diet; D059305:Diet, High-Fat; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000032:analysis; D004041:Dietary Fats / Q000008:administration & dosage / Q000032:analysis; D004044:Dietary Proteins / Q000008:administration & dosage / Q000032:analysis; D002149:Energy Intake; D015444:Exercise / Q000502:physiology*; D005260:Female; D006339:Heart Rate; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D016014:Linear Models; D050356:Lipid Metabolism; D010101:Oxygen Consumption; D015203:Reproducibility of Results; D055815:Young Adult
chemical_list: D001786:Blood Glucose; D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D002245:Carbon Dioxide; D019344:Lactic Acid
keywords: diet manipulation; exercice physique; exercise; exercise metabolism; fiabilité; modification du régime alimentaire; métabolisme à l’effort; oxydation des substrats; physiological testing; reliability; substrate oxidation; test physiologique