Obesity-induced decreases in muscle performance are not reversed by weight loss.
Obesity can affect muscle phenotypes, and may thereby constrain movement and energy expenditure. Weight loss is a common and intuitive intervention for obesity, but it is not known whether the effects of obesity on muscle function are reversible by weight loss. Here we tested whether obesity-induced changes in muscle metabolic and contractile phenotypes are reversible by weight loss.



We used zebrafish (Danio rerio) in a factorial design to compare energy metabolism, locomotor capacity, muscle isometric force and work-loop power output, and myosin heavy chain (MHC) composition between lean fish, diet-induced obese fish, and fish that were obese and then returned to lean body mass following diet restriction.



Obesity increased resting metabolic rates (P<0.001) and decreased maximal metabolic rates (P=0.030), but these changes were reversible by weight loss, and were not associated with changes in muscle citrate synthase activity. In contrast, obesity-induced decreases in locomotor performance (P=0.0034), and isolated muscle isometric stress (P=0.01), work-loop power output (P<0.001) and relaxation rates (P=0.012) were not reversed by weight loss. Similarly, obesity-induced decreases in concentrations of fast and slow MHCs, and a shift toward fast MHCs were not reversed by weight loss.



Obesity-induced changes in locomotor performance and muscle contractile function were not reversible by weight loss. These results show that weight loss alone may not be a sufficient intervention.
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
F
F
Seebacher
Centre for Applied Biological and Exercise Sciences, Coventry University, Coventry, UK.
J
J
Tallis
School of Life and Environmental Sciences, University of Sydney, Sydney, NSW, Australia.
K
K
McShea
Centre for Applied Biological and Exercise Sciences, Coventry University, Coventry, UK.
R S
RS
James
D000818:Animals; D001481:Basal Metabolism / Q000502:physiology; D004195:Disease Models, Animal; D004734:Energy Metabolism; D009043:Motor Activity; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000378:metabolism / Q000503:physiopathology*; D018995:Myosin Heavy Chains / Q000378:metabolism; D009765:Obesity / Q000378:metabolism / Q000503:physiopathology*; D010805:Physical Conditioning, Animal; D013550:Swimming / Q000502:physiology; D015431:Weight Loss; D015027:Zebrafish
D018995:Myosin Heavy Chains