title: Substrate utilization during exercise in formerly morbidly obese women.
abstract: The purpose of this study was to compare substrate utilization during fasting and submaximal exercise in morbidly obese women after weight loss (WL) with that in weight-matched controls (C). WL were studied in the weight-stable condition approximately 24 mo after gastric bypass surgery. Energy intake (self-reported) and expenditure ((2)H(2)(18)O) were also compared. The respiratory exchange ratio during exercise at the same absolute (15 W) workload was significantly (P < or = 0.05) elevated in WL vs. C (0.90 +/- 0.02 vs. 0.83 +/- 0.03); this was reflected as lower fat utilization in WL (29.7 +/- 4.8 vs. 53.2 +/- 9.7% of energy from fat). Respiratory exchange ratio during exercise at the same relative (65% of maximal O(2) uptake) intensity was also significantly (P < 0.05) elevated in WL (0.96 +/- 0.01 vs. 0.89 +/- 0.02), and fat use was concomitantly depressed (12.4 +/- 3.0 vs. 34.3 +/- 9.9% of energy from fat). Resting substrate utilization, daily energy expenditure, and self-reported relative macronutrient intake did not differ between groups. These data suggest that lipid oxidation is depressed during physical activity in WL. This defect may, at least in part, contribute to a propensity for the development of morbid obesity.
authors.affiliation: Human Performance Laboratory, East Carolina University, Greenville, North Carolina 27858, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Guesbeck
authors.forename: M S
authors.initials: MS
authors.lastname: Hickey
authors.forename: K G
authors.initials: KG
authors.lastname: MacDonald
authors.forename: W J
authors.initials: WJ
authors.lastname: Pories
authors.forename: I
authors.initials: I
authors.lastname: Harper
authors.forename: E
authors.initials: E
authors.lastname: Ravussin
authors.forename: G L
authors.initials: GL
authors.lastname: Dohm
authors.forename: J A
authors.initials: JA
authors.lastname: Houmard
mesh_terms: D000328:Adult; D015992:Body Mass Index; D001835:Body Weight; D003903:Deuterium; D002149:Energy Intake; D004734:Energy Metabolism; D015444:Exercise / Q000502:physiology*; D005215:Fasting / Q000502:physiology; D005260:Female; D006339:Heart Rate; D006801:Humans; D009767:Obesity, Morbid / Q000503:physiopathology* / Q000601:surgery; D010101:Oxygen Consumption / Q000502:physiology*; D010103:Oxygen Isotopes; D005082:Physical Exertion / Q000502:physiology*; D012016:Reference Values; D015656:Respiratory Mechanics; D015431:Weight Loss / Q000502:physiology*
chemical_list: D010103:Oxygen Isotopes; D003903:Deuterium