title: Enhanced fat oxidation through physical activity is associated with improvements in insulin sensitivity in obesity.
abstract: Skeletal muscle insulin resistance entails dysregulation of both glucose and fatty acid metabolism. This study examined whether a combined intervention of physical activity and weight loss influences fasting rates of fat oxidation and insulin-stimulated glucose disposal. Obese (BMI >30 kg/m(2)) volunteers (9 men and 16 women) without diabetes, aged 39 +/- 4 years, completed 16 weeks of moderate-intensity physical activity combined with caloric reduction. Body composition was determined by dual-energy X-ray absorptiometry and computed tomography. Glucose disposal rates (R(d)) were measured during euglycemic hyperinsulinemia (40 mU x m(-2) x min(-1)), and substrate oxidation was determined via indirect calorimetry. Fat mass and regional fat depots were reduced and VO(2max) improved by 19%, from 38.8 +/- 1.2 to 46.0 +/- 1.0 ml x kg fat-free mass (FFM)(-1) x min(-1) (P < 0.05). Insulin sensitivity improved 49 +/- 10% (6.70 +/- 0.40 to 9.51 +/- 0.51 mg x min(-1) x kg FFM(-1); P < 0.05). Rates of fat oxidation following an overnight fast increased (1.16 +/- 0.06 to 1.36 +/- 0.05 mg x min(-1) x kg FFM(-1); P < 0.05), and the proportion of energy derived from fat increased from 38 to 52%. The strongest predictor of the improved insulin sensitivity was enhanced fasting rates of fat oxidation, accounting for 52% of the variance. In conclusion, exercise combined with weight loss enhances postabsorptive fat oxidation, which appears to be a key aspect of the improvement in insulin sensitivity in obesity.
authors.affiliation: Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
authors.forename: Bret H
authors.initials: BH
authors.lastname: Goodpaster
authors.forename: Andreas
authors.initials: A
authors.lastname: Katsiaras
authors.forename: David E
authors.initials: DE
authors.lastname: Kelley
mesh_terms: D000005:Abdomen; D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D001823:Body Composition; D004038:Diet, Reducing; D002149:Energy Intake; D005215:Fasting; D005223:Fats / Q000378:metabolism*; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism; D009765:Obesity / Q000178:diet therapy / Q000378:metabolism*; D010084:Oxidation-Reduction; D010809:Physical Fitness; D015431:Weight Loss
chemical_list: D005223:Fats