title: Resting metabolic rate and postprandial thermogenesis by level of aerobic fitness in young women.
abstract: Resting metabolic rate (RMR) and the thermic effect of a meal (TEM) were compared among women of three levels of aerobic fitness. Twenty-three euthyroid, eumenorrheic women (aged 18-35 years) were divided into three groups based on VO2 max standardized for fat-free weight (FFW), as determined from a graded exercise test: High Fit (HF): n = 7, VO2 max > 70 ml*kg FFW-1*min-1; Moderately Fit (MF): n = 8, VO2 max = 55-70 ml*kg FFW-1*min-1; and Low Fit (LF): n = 8, VO2 max < 55 ml*kg FFW-1*min-1). At 0700h RMR was measured for 1 h by indirect calorimetry with subjects in a fasted, preovulatory state, having refrained from exercise on the preceding day. The subject then consumed a liquid meal (12 kcal*kg FFW-1) and indirect calorimetry was continued for 3 h to determine the TEM. RMR adjusted for FFW using analysis of covariance was significantly higher (P < 0.05) in the HF group (mean +/- SEM = 1.08 +/- 0.03 kcal*min-1) compared to the MF (0.99 +/- 0.04) and LF (0.90 +/- 0.04) groups. Group differences in the thermic response did not reach statistical significance, although there was a trend for a high TEM in the HF group. There was a positive relationship between RMR and energy flux (average daily kcalorie intake + daily kcaloric expenditure in physical activity). These results suggest that women who exhibit high levels of exercise and aerobic fitness may be less energy efficient during the non-exercise portion of the day then their less active counterparts.
authors.affiliation: Department of Food Science and Human Nutrition, Colorado State University, Ft. Collins 80523.
authors.forename: C M
authors.initials: CM
authors.lastname: Burke
authors.forename: R C
authors.initials: RC
authors.lastname: Bullough
authors.forename: C L
authors.initials: CL
authors.lastname: Melby
mesh_terms: D000273:Adipose Tissue; D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D001481:Basal Metabolism; D001823:Body Composition; D001833:Body Temperature Regulation; D001835:Body Weight; D002153:Calorimetry, Indirect; D003430:Cross-Sectional Studies; D004435:Eating; D002149:Energy Intake; D004734:Energy Metabolism; D005080:Exercise Test; D005215:Fasting; D005260:Female; D005498:Follicular Phase; D006801:Humans; D010101:Oxygen Consumption; D010809:Physical Fitness; D012146:Rest