TY - JOUR

T1 - No diurnal variation is present in maximal fat oxidation during exercise in young healthy women

T2 - A cross-over study

AU - Robles-González, Lidia

AU - Aguilar-Navarro, Millán

AU - López-Samanes, Álvaro

AU - Ruiz-Moreno, Carlos

AU - Muñoz, Alejandro

AU - Varillas-Delgado, David

AU - Gutiérrez-Hellín, Jorge

AU - Helge, Jørn W.

AU - Ruiz, Jonatan R.

AU - Amaro-Gahete, Francisco J.

N1 - Publisher Copyright: © 2022 European College of Sport Science.

PY - 2023

Y1 - 2023

N2 - Maximal fat oxidation during exercise (MFO) and the intensity that elicits MFO (Fatmax) seems to show a diurnal variation in men, which favours an increased performance in the afternoon than the morning. At present, it remains unknown whether the observed MFO and Fatmax diurnal variation in men is also present in women. Therefore, the current study examined the diurnal variations of MFO and Fatmax in women. Nineteen healthy women (age: 26.9 ± 8.7 years, maximum oxygen uptake: 39.8 ± 6.5 ml/kg/min) participated in the study. MFO and Fatmax were determined by a graded exercise test in cycloergometer using a cross-over design performed on two separate daytime schedules, one conducted in the morning (8am–11am) and one in the afternoon (5pm–8pm). Stoichiometric equations were used to calculate fat oxidation rates. There were no significant differences between MFO-morning and MFO-afternoon (0.24 ± 0.10 vs. 0.23 ± 0.07 g/min, respectively; P = 0.681). Similarly, there was no significant differences between Fatmax-morning and Fatmax-afternoon (41.1 ± 4.7 vs. 42.6 ± 5.5% of maximal oxygen uptake, respectively; P = 0.305). These results persisted after controlling for fat mass percentage (all P > 0.5). In summary, the main finding of the present study was that MFO and Fatmax were similar independent of the time-of-day when the exercise test is performed in healthy women. These results have important clinical implications since they suggest that, in contrast to what was found in men, MFO and Fatmax show similar rates during the course of the day in women. Highlights MFO and Fatmax were similar during the afternoon and morning in young healthy women. Our results suggest that, in women, it does not matter when endurance exercise is performed in term of fat metabolism during exercise.

AB - Maximal fat oxidation during exercise (MFO) and the intensity that elicits MFO (Fatmax) seems to show a diurnal variation in men, which favours an increased performance in the afternoon than the morning. At present, it remains unknown whether the observed MFO and Fatmax diurnal variation in men is also present in women. Therefore, the current study examined the diurnal variations of MFO and Fatmax in women. Nineteen healthy women (age: 26.9 ± 8.7 years, maximum oxygen uptake: 39.8 ± 6.5 ml/kg/min) participated in the study. MFO and Fatmax were determined by a graded exercise test in cycloergometer using a cross-over design performed on two separate daytime schedules, one conducted in the morning (8am–11am) and one in the afternoon (5pm–8pm). Stoichiometric equations were used to calculate fat oxidation rates. There were no significant differences between MFO-morning and MFO-afternoon (0.24 ± 0.10 vs. 0.23 ± 0.07 g/min, respectively; P = 0.681). Similarly, there was no significant differences between Fatmax-morning and Fatmax-afternoon (41.1 ± 4.7 vs. 42.6 ± 5.5% of maximal oxygen uptake, respectively; P = 0.305). These results persisted after controlling for fat mass percentage (all P > 0.5). In summary, the main finding of the present study was that MFO and Fatmax were similar independent of the time-of-day when the exercise test is performed in healthy women. These results have important clinical implications since they suggest that, in contrast to what was found in men, MFO and Fatmax show similar rates during the course of the day in women. Highlights MFO and Fatmax were similar during the afternoon and morning in young healthy women. Our results suggest that, in women, it does not matter when endurance exercise is performed in term of fat metabolism during exercise.

KW - circadian rhythm

KW - fat oxidation

KW - Fat

KW - female

KW - MFO

UR - http://www.scopus.com/inward/record.url?scp=85132615644&partnerID=8YFLogxK

U2 - 10.1080/17461391.2022.2067007

DO - 10.1080/17461391.2022.2067007

M3 - Journal article

C2 - 35437101

AN - SCOPUS:85132615644

VL - 23

SP - 936

EP - 942

JO - European Journal of Sport Science

JF - European Journal of Sport Science

SN - 1746-1391

IS - 6

ER -