Background/Objectives: Impaired insulin-mediated glucose partitioning is an intrinsic metabolic defect in skeletal muscle from severely obese humans (BMI ≥ 40 kg/m 2). Roux-en-Y gastric bypass (RYGB) surgery has been shown to improve glucose metabolism in severely obese humans. The purpose of the study was to determine the effects of RYGB surgery on glucose partitioning, mitochondrial network morphology, and markers of mitochondrial dynamics skeletal muscle from severely obese humans. Subject/Methods: Human skeletal muscle cells were isolated from muscle biopsies obtained from RYGB patients (BMI = 48.0 ± 2.1, n=7) prior to, 1-month and 7-months following surgery and lean control subjects (BMI = 22.4 ± 1.1, n=7). Complete glucose oxidation, non-oxidized glycolysis rates, mitochondrial respiratory capacity, mitochondrial network morphology and regulatory proteins of mitochondrial dynamics were determined in differentiated human myotubes. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use: