Skeletal muscle metabolic characteristics before and after energy restriction in human obesity: fibre type, enzymatic beta-oxidative capacity and fatty acid-binding protein content

Background Skeletal muscle has the ability to adapt as result of dietary, h ormonal or pharmacological interventions affecting energy metabolism. The a im of the present study was to investigate the effects of energy restrictio n on skeletal muscle metabolic characteristics in obese women. Methods The effects of 8 weeks' energy restriction on body composition, ene rgy expenditure and skeletal muscle characteristics were investigated in 28 healthy obese women. Subjects were aged 37 . 9 +/- 1 . 5 years and had a b ody mass index of 32 . 0 +/- 0 . 8 kg m(-2). Results Energy restriction (2800 kJ day(-1)) resulted in a 10 . 8 +/- 0 . 5 kg weight loss consisting of 8 . 6 +/- 0 . 5 kg of fat mass and 2 . 2 +/- 0 . 3 kg of fat-free mass. Basal respiratory exchange ratio, sleeping metab olic rate and exercise-induced thermogenesis significantly declined in resp onse to the diet. These changes were accompanied by an increase (P = 0 . 03 8) in the skeletal muscle content of cytosolic fatty acid-binding protein ( H-FABP), whereas no changes occurred in fibre type distribution or activiti es of enzymes reflecting beta-oxidation and mitochondrial density (3-hydrox yacyl-CoA dehydrogenase and citrate synthase respectively). Conclusion The results suggest that increased capacity of intracellular fat ty acid transport in skeletal muscle cells is involved in the physiological adaptations of fat metabolism to energy restriction in obese female subjec ts.