OBJECTIVE:We examined three methods for calculating the area under the curve (AUC) following an oral glucose tolerance test (OGTT) in overweight adults prior to and after 9 months of exercise. METHOD: Subjects (n ¼ 27) were randomly assigned to a control (CON, n ¼ 9) or intervention (INT, n ¼ 18) group. INT performed supervised exercise 5 days per week, 45 min per session, at 65% of heart rate reserve. OGTTs were administered preand post-training. Blood was collected during a 75 g OGTT and analyzed for glucose (GLU) and insulin (INS) concentrations. AUCs were calculated using the incremental, positive incremental, and total AUC methods and the difference scores for pre-and post-training were determined. RESULTS: No differences were observed among the methods for glucose AUC for either group. Significant differences were observed for INT insulin AUC with total AUC (1525 AE 3291 mU=1=180 min) significantly greater than incremental AUC (1112 AE 3229 mU=1=180 min) or positive incremental AUC (1085 AE 3195 mU=I=180 min). Total insulin AUC was significantly reduced following training for INT, while incremental and positive incremental insulin AUCs showed no change. CONCLUSION: These data suggest that the method of used to calculate AUC may affect the interpretation of whether or not an intervention was effective.
Background: Diets high in either dairy or calcium during moderate weight reduction both prevent loss of bone mineral density (BMD) and suppress bone turnover. The purpose of this study was to determine whether recommended dairy and calcium intakes during weight maintenance favorably affect total body BMD (TBBMD) and bone mineral content (TBBMC) in obese adults. Methods: Obese men (n ¼ 49) and women (n ¼ 64), aged 40.8 ± 0.6 years, underwent 12 weeks of moderate energy restriction (B1200 kcal/day) followed by 24 weeks on either a low or recommended dairy weight maintenance diet. The TBBMC and TBBMD values were measured using dual energy X-ray absorptiometry at baseline, 12, 24 and 36 weeks. Concentrations of calcium, intact parathyroid hormone (iPTH), 25OH and 1,25 (OH) 2 vitamin D in plasma were also measured. Data were analyzed using a two-factor repeated measures analysis of variance. Results: After weight loss, women exhibited a small, but statistically significant, increase in TBBMC (1.17±0.57%), whereas TBBMD increased in the men (1.34 ± 0.28%). The iPTH concentration decreased significantly in all subjects. Despite significantly greater intakes of calcium, vitamin D and protein compared with the recommended dairy diet, there were no treatment-related differences in outcome variables after 24 weeks of weight maintenance. The TBBMC remained unchanged in women during weight stabilization; both TBBMC and TBBMD decreased in men (À1.59±0.51% and À0.70±0.25%, respectively). Conclusions: In summary, results of this study do not provide convincing evidence that moderate weight loss through energy restriction and mild exercise reduces TBBMC in obese men and women. Similarly, a weight-maintenance diet providing the recommended daily servings of dairy does not seem to affect changes in BMC after weight loss.
OBJECTIVE:To determine the time course for changes in aerobic capacity, body weight (BW), and composition in overweight adults in response to a supervised exercise trial with a targeted energy expenditure of 2000 kcal week À1 . DESIGN: The Midwest Exercise Trial (MET) was a randomized, controlled, 16-month verified, supervised exercise trial. Aerobic exercise progressed to 45 min day À1 , 5 days week À1 over 6-months and was then maintained for 10 months. Controls maintained their normal physical activity and all participants maintained ad libitum diets. SUBJECTS: A total of 131 participants were randomized to exercise or control groups and 74 completed the intervention and all laboratory testing. MEASUREMENTS: At baseline and months 4, 9, 12, and 16, aerobic capacity (VO 2max ) was measured by indirect calorimetry, BW by digital scale, and fat weight and fat-free weight by hydrostatic weighing. RESULTS: Aerobic capacity (ml kg À1 min À1 ) increased (Po0.05) from baseline (39.275.2, mean7s.d.) to 9 months (48.874.3) in exercising men as well as women (32.874.2-39.675.5) with no significant changes occurring at 12 or 16 months. From baseline to 9 months BW (94.0712.6-88.779.7 kg) and fat weight (26.876.8-21.874.5 kg) significantly decreased in exercising men with no changes occurring at 12 or 16 months. There were no changes in fat-free weight across the 16 months for exercising men or for BW or composition in exercising women. Further, there were no significant changes for the control men for aerobic capacity, BW, or body composition across 16 months. Women in the control group showed significant increases in weight of 2.975.5 kg and fat weight of 2.174.8 kg at 16 months only. CONCLUSIONS: We recommend that investigations that use exercise without diet as the stimulus for weight loss have at least a 9-month duration to provide sufficient time for the full effects to be realized, should such effects be present.
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