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The purpose of this study was to discern cellular mechanisms that contribute to the suppression of lipid oxidation in the skeletal muscle of obese individuals. Muscle was obtained from obese [body mass index (BMI), 38.3 ± 3.1 kg/m²] and lean (BMI, 23.8 ± 0.9 kg/m²) women, and fatty acid oxidation was studied by measuring ¹⁴CO₂ production from¹⁴C-labeled fatty acids. Palmitate oxidation, which is at least partially dependent on carnitine palmitoyltransferase-1 (CPT-1) activity, was depressed (P < 0.05) by ≈50% with obesity (6.8 ± 2.2 vs. 13.7 ± 1.4 nmole CO₂ · g⁻¹ · h⁻¹). The CPT-1-independent event of palmitoyl carnitine oxidation was also depressed (P < 0.01) by ≈45%. There were significant negative relationships (P < 0.05) for adiposity with palmitate (r = −0.76) and palmitoyl carnitine (r = −0.82) oxidation. Muscle CPT-1 and citrate synthase activity, an index of mitochondrial content, were also significantly …