Differences in resting metabolic rates of inactive obese African-American and Caucasian women.
OBJECTIVE
To compare resting metabolic rates (RMR) of African-American (n = 25) and Caucasian (n = 22) premenopausal (35+/-1 y, Mean +/- s.e.m.) women who are obese (95.2+/-2.9 kg, body mass index (BMI) = 34.7+/-0.9, % body fat = 45.2+/-0.9), inactive and free from metabolic disorders or medications that would affect heart rate or RMR.


METHODS
RMR and respiratory exchange ratio (RER) by indirect calorimetry, body composition by plethysmography, maximal aerobic capacity (VO2max) and girth measurements.


RESULTS
Group mean comparisons were made with a Student's t-test or an ANCOVA, which controlled for individual differences in body weight and lean body mass (LBM). Significance was set at P < 0.05. Groups were not significantly different in age, height, weight, BMI, % body fat, fat mass, RER, VO2max, resting heart rate, maximal heart rate; or chest, waist, hip, arm, thigh or calf circumferences. After adjusting for body weight, RMR (I O2/min) for African-Americans (0.254+/-0.007) was significantly lower (9%) than for Caucasians (0.277+/-0.008). After RMR (I O2/min) was adjusted for LBM, an even larger difference (-12%) persisted for African-Americans (0.250+/-0.008) compared to Caucasians (0.281+/-0.008). Predicted RMR (kJ/d) for the African-Americans was the same as measured RMR, whereas Caucasian women expended about 13% more energy than predicted. When controlling for LBM, the partial correlation between VO2max and RMR was r=0.51 when VO2max was expressed as I/min, and r=0.56 when VO2max was expressed as ml O2/kg/min, both highly significant (P < 0.000).


CONCLUSIONS
The lower prevalence of obesity in Caucasian women may be due in part to a higher RMR as well as an under estimation of RMR in weight control therapy. Fitness level (VO2max) as well as LBM are significant predictors of RMR for both races.
Forman
J N
JN
Exercise Science Programs, The George Washington University Medical Center, Washington, DC 20052, USA.
Miller
W C
WC
Szymanski
L M
LM
Fernhall
B
B
D000328:Adult; D001481:Basal Metabolism / Q000502:physiology*; D044383:Black People; D001823:Body Composition; D001835:Body Weight / Q000502:physiology*; D002153:Calorimetry, Indirect; D015331:Cohort Studies; D005260:Female; D006801:Humans; D009765:Obesity / Q000208:ethnology / Q000378:metabolism* / Q000503:physiopathology; D010101:Oxygen Consumption / Q000502:physiology*; D017697:Premenopause / Q000378:metabolism*; D044465:White People; D001741:Black or African American