A comparison of methods for analyzing glucose and insulin areas under the curve following nine months of exercise in overweight adults

Abstract

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. Subjects (n=27) were randomly assigned to a control (CON, n=9) or intervention (INT, n=18) group. INT performed supervised exercise 5 days per week, 45 min per session, at 65% of heart rate reserve. OGTTs were administered pre- and 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. 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+/-3291 microU/1/180 min) significantly greater than incremental AUC (1112+/-3229 microU/1/180 min) or positive incremental AUC (1085+/-3195 microU/I/180 min). Total insulin AUC was significantly reduced following training for INT, while incremental and positive incremental insulin AUCs showed no change. These data suggest that the method of used to calculate AUC may affect the interpretation of whether or not an intervention was effective.