Data from: Obesity-induced decreases in muscle performance are not reversed by weight loss

BACKGROUND/OBJECTIVES: 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. SUBJECTS/METHODS: 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. RESULTS: Obesity increased
resting metabolic rates (Po0.001) 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
(Po0.001) 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.
CONCLUSION: 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.