objective:To determine what effect diet-induced ~12 kg weight loss in combination with exercise training has on body composition and resting energy expenditure (REE) in premenopausal African-American (AA) and European-American (EA) women. Methods and Procedures: This study was a longitudinal, randomized weight loss clinical intervention, with either aerobic (AT), resistance (RT), or no exercise training (NT). Forty-eight AA and forty-six EA premenopausal overweight (BMI between 27 and 30) women underwent weight loss to a BMI <25. Body composition (densitometry), REE (indirect calorimetry), maximal oxygen uptake (VO 2 max), and muscular strength (isometric elbow flexion) were evaluated when subjects were in energy balance. Results: AA women lost less fat-free mass (FFM, P ≤ 0.05) (47.0 ± 4.6 to 46.9 ± 5.0 kg) than EA women (46.4 ± 4.9 to 45.2 ± 4.6 kg). Regardless of race, RT maintained FFM (P ≤ 0.05) following weight loss (46.9 ± 5.2 to 47.2 ± 5.0 kg) whereas AT (45.4 ± 4.2 to 44.4 ± 4.1 kg) and NT (47.9 ± 4.7 to 46.4 ± 5.1 kg) decreased FFM (P ≤ 0.05). Both AT and NT decreased in REE with weight loss but RT did not. Significant time by group interactions (all P ≤ 0.05) for strength indicated that RT maintained strength and AT did not. Discussion: AA women lost less FFM than EA women during equivalent weight losses. However, following weight loss in both AA and EA, RT conserved FFM, REE, and strength fitness when compared to women who AT or did not train.

Premenopausal women overestimate PA estimates on questionnaires. Overestimation of PA in weight-reduced black women is greater than in weight-reduced white women and never-overweight black and white women.

Objective: To determine the relationship between body composition/fat distribution and parity after adjusting for potential confounders: age, smoking, and physical activity. Design: Cross-sectional. Subjects: A total of 170 Caucasian women between the ages of 18 and 76 years, who were non-smokers with no cardiovascular disease, diabetes, metabolic, or endocrine disorders. Measurements: Physical activity assessment (Baecke Physical Activity Questionnaire), anthropometric measures, and body composition (dual-energy X-ray absorptiometry, computed tomography). Results: Although percent body fat was related to parity (r ¼ 0.26, Po0.01), after adjusting for age, physical activity index, and smoking, the parity-percent body fat relationship was no longer significant. Multiple regression analysis for modeling intra-abdominal adipose tissue demonstrated that parity and intra-abdominal adipose tissue were significantly related after adjusting for percent body fat, physical activity index, and smoking (partial r ¼ 0.18, P ¼ 0.02, unstandardized b ¼ 5.2272.26, intercept ¼ À37.32724.63). Conclusion: Our data suggest that intra-abdominal adipose tissue increases with increasing parity, even after adjusting for potential confounders: age, percent body fat, physical activity, and smoking.

HUNTER, GARY R., NUALA M. BYRNE, BARBARA A. GOWER, BOVORN SIRIKUL, AND ANDREW P. HILLS. Increased resting energy expenditure after 40 minutes of aerobic but not resistance exercise. Obesity. 2006;14:2018 -2025. Objective: Resting energy expenditure (REE) is increased 24 hours after high-intensity aerobic exercise lasting 60 minutes, whereas results have been inconsistent after resistance training and aerobic exercise of shorter duration. The objective of the study was to compare the effects of 40 minutes of high-intensity aerobic vs. resistance exercise on REE 19 to 67 hours after exercise. Research Methods and Procedures: REE was compared 19, 43, and 67 hours after 40 minutes of aerobic training (AT; 80% maximum heart rate) or resistance training (RT; 10 repetitions at 80% maximum strength, two sets and eight exercises). Twenty-three black and 22 white women were randomly assigned to AT, RT, or no training (controls). Exercisers trained 25 weeks. REE was measured after a 12-hour fast. Results: There was a significant time ϫ group interaction for REE when adjusted for fat-free mass and fat mass, with post hoc tests revealing that the 50-kcal difference between 19 and 43 hours (1310 Ϯ 196 to 1260 Ϯ 161 kcal) and the 34-kcal difference between 19 and 67 hours (1310 Ϯ 196 to 1276 Ϯ 168 kcal) were significant for AT. No other differences were found, including RT (19 hours, 1256 Ϯ 160; 43 hours, 1251 Ϯ 160; 67 hours, 1268 Ϯ 188 kcal). Urine norepinephrine increased with training only in AT. After adjusting for fat-free mass, REE ⌬ between 19 and both 43 and 67 hours was significantly related to urine norepinephrine (r ϭ 0.76, p Ͻ 0.01 and 0.68, p Ͻ 0.03, respectively). Discussion: Consistent with findings on longer duration AT, these results show that 40 minutes of AT elevates REE for 19 hours in trained black and white women. This elevation did not occur with 40 minutes of RT. Results suggest that differences are, in part, due to increased sympathetic tone.

Recent data have shown that individuals with low insulin sensitivity (S(I)) also have reduced whole body maximal oxygen uptake. The objectives of this study were to determine 1) whether muscle mitochondrial function was independently related to S(I) after being adjusted for known determinants of S(I) and 2) whether lower S(I) among African-American (AA) vs. Caucasian-American (CA) women was due to lower muscle mitochondrial function among AA women. Subjects were 37 CA and 22 AA premenopausal women (age: 33.6 +/- 6.3 yr). Mitochondrial function [time constant of ADP (ADP(tc))] was assessed during a 90-s unilateral isometric contraction using (31)P magnetic resonance spectroscopy, S(I) with an intravenous glucose tolerance test, body composition by dual-energy X-ray absorptiometry, and visceral adipose tissue (VAT) with computed tomography. ANOVA was used to compare AA and CA groups, and multiple linear regression modeling was used to identify independent predictors of S(I). Between-race comparisons indicated that muscle oxidative capacity was lower among AAs vs. CAs (ADP(tc): 25.6 +/- 9.8 vs. 21.4 +/- 9.9 s). Multiple linear regression models for the dependent variable S(I) contained 1) VAT and race and 2) VAT, race, and ADP(tc). Significant independent effects for all predictor variables were observed in both the first (r(2) = 0.345) and second (r(2) = 0.410) models. The partial correlation for race was lower in the second model (-0.404 vs. -0.300), suggesting that muscle mitochondrial function contributed to the racial difference in S(I). Lower muscle mitochondrial function among AAs may in part explain lower S(I) among them.

The prevalence of type 2 diabetes is greater among African Americans (AA) vs. European Americans (EA), independent of obesity and lifestyle. We tested the hypothesis that intramyocellular lipid (IMCL) or extramycellular lipid (EMCL) would be associated with insulin sensitivity among healthy young women, and that the associations would differ with ethnic background. We also explored the hypothesis that adipokines and estradiol would be associated with muscle lipid content. Participants were 57 healthy, normoglycemic, women and girls mean age 26 (±10) years; mean BMI 27.3 (±4.8) kg/m2; 32 AA, 25 EA. Soleus IMCL and EMCL were assessed with 1H magnetic resonance spectroscopy (MRS); insulin sensitivity with an insulin-modified frequently sampled intravenous glucose tolerance test and minimal modeling; body composition with dual-energy X-ray absorptiometry; and intra-abdominal adipose tissue (IAAT) with computed tomography. Adiponectin, leptin, and estradiol were assessed in fasting sera. Analyses indicated that EMCL, but not IMCL, was greater in AA vs. EA (2.55 ± 0.16 vs. 1.98 ± 0.18 arbitrary units, respectively, P < 0.05; adjusted for total body fat). IMCL was associated with insulin sensitivity in EA (r = −0.54, P < 0.05, adjusted for total fat, IAAT, and age), but not AA (r = 0.16, P = 0.424). IMCL was inversely associated with adiponectin (r = −0.31, P < 0.05, adjusted for ethnicity, age, total fat, and IAAT). In conclusion, IMCL was a significant determinant of insulin sensitivity among healthy, young, EA but not AA women. Further research is needed to determine whether the component lipids of IMCL (e.g., diacylglycerol (DAG) or ceramide) are associated with insulin sensitivity in an ethnicity-specific manner.

Little is known concerning the contributions of oxidative phosphorylation (OxPhos), anaerobic glycolytic rate (AnGly), maximum creatine kinase (CK) activity, and metabolic economy (ME) on fatigue resistance. The purpose of this study was to model fatigue using muscle tissue metabolic measures during a maximal short-duration isometric contraction. Muscle metabolic function was measured with [31P]-magnetic resonance spectroscopy (MRS) in 54 premenopausal women (age: 33.8+/-6.3 y) while they performed 100% isometric plantar flexions. Multiple regression analysis revealed that all metabolic variables were independent predictors of fatigue resistance after adjusting for maximum isometric force generated (R2=0.56). ME accounted for the largest portion (36%) of overall shared variance. OxPhos accounted for the most shared variance of the three energy systems. These results support previous findings that OxPhos, AnGly, CK, and ME all contribute to fatigue resistance over a short duration. Additionally, the continued activity of CK at the end of 90 s of maximal exercise lends support to the concept of a CK shuttle facilitating energy transfer within the mitochondria.

In a postprandial state, prolonged exercise stimulates glucagon and cortisol increases that are associated with stable blood glucose and leptin concentrations; however, similar to postprandial state control condition, insulin, C-peptide, and amylin concentrations decline.