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Appl Physiol Nutr Metab. 2015 Dec;40(12):1262-8. doi: 10.1139/apnm-2015-0258. Epub 2015 Aug 17.

Effect of 1-h moderate-intensity aerobic exercise on intramyocellular lipids in obese men before and after a lifestyle intervention.

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a The University of Queensland Diamantina Institute, Brisbane, Australia.
b School of Human Movement and Nutrition Sciences, University of Queensland, Brisbane, Australia.
c Mater Research Institute, University of Queensland, Brisbane, Australia.
d Faculty of Physical Education and Sports, Université de Sherbrooke, Sherbrooke, Quebec, Canada.
e Bond Institute of Health and Sport, Bond University, Robina, Australia.
f Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia.
g Centre for Advanced Imaging, University of Queensland, Brisbane, Australia.
h Department of Diabetes and Endocrinology, Princess Alexandra Hospital, Brisbane, Australia.


Intramyocellular lipids (IMCL) are depleted in response to an acute bout of exercise in lean endurance-trained individuals; however, it is unclear whether changes in IMCL content are also seen in response to acute and chronic exercise in obese individuals. We used magnetic resonance spectroscopy in 18 obese men and 5 normal-weight controls to assess IMCL content before and after an hour of cycling at the intensity corresponding with each participant's maximal whole-body rate of fat oxidation (Fatmax). Fatmax was determined via indirect calorimetry during a graded exercise test on a cycle ergometer. The same outcome measures were reassessed in the obese group after a 16-week lifestyle intervention comprising dietary calorie restriction and exercise training. At baseline, IMCL content decreased in response to 1 h of cycling at Fatmax in controls (2.8 ± 0.4 to 2.0 ± 0.3 A.U., -39%, p = 0.02), but not in obese (5.4 ± 2.1 vs. 5.2 ± 2.2 A.U., p = 0.42). The lifestyle intervention lead to weight loss (-10.0 ± 5.4 kg, p < 0.001), improvements in maximal aerobic power (+5.2 ± 3.4 mL/(kg·min)), maximal fat oxidation rate (+0.19 ± 0.22 g/min), and a 29% decrease in homeostasis model assessment score (all p < 0.05). However, when the 1 h of cycling at Fatmax was repeated after the lifestyle intervention, there remained no observable change in IMCL (4.6 ± 1.8 vs. 4.6 ± 1.9 A.U., p = 0.92). In summary, there was no IMCL depletion in response to 1 h of cycling at moderate intensity either before or after the lifestyle intervention in obese men. An effective lifestyle intervention including moderate-intensity exercise training did not impact rate of utilisation of IMCL during acute exercise in obese men.


diet; diète; ectopic fat; energy metabolism; entraînement physique; exercise training; graisse ectopique; intramyocellular triglycerides; magnetic resonance spectroscopy; maximal fat oxidation; muscle; métabolisme énergétique; obesity; obésité; oxydation maximale des graisses; spectroscopie par résonance magnétique; triglycérides intramyocellulaires

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