Controlling subjects' prior diet and activities does not reduce within-subject variation of postprandial glycemic responses to foods

Glycemic responses to the same food vary from day-to-day within subjects. To determine whether controlling the subjects' activities and dinner the night before a standard breakfast reduces the within-subject variability of glycemic responses. Thirteen healthy subjects performed 4 controlled and 4 uncontrolled trials in a randomized block design. The controlled trials entailed no vigorous exercise for 24 hrs, consumption of a standard dinner, and set fast length (+/- 15 minutes). The uncontrolled trials entailed usual activity, no standard dinner, and a fast between 10-14 hours), after which a two-hour blood glucose response to a standard breakfast meal was quantified for both trial types. The within-subject coefficient of variation (CV) of the area under the glycemic response curves (AUC) were calculated. The mean CV of controlled trials, 24.3%, was not significantly different from that of the uncontrolled trials, 20.4%. However, the controlled CV values were higher in 10 of 13 subjects (p < 0.05; one-tailed). The method used here of controlling subjects' activities and dinner the night before a glycemic response test did not reduce within-subject blood glucose variability. (C) 2003 Elsevier Inc. All rights reserved.