ObjectiveThe purpose of this study was to compare the effects Cassia cinnamon and cellulose placebo on oral glucose tolerance test (OGTT) blood glucose (BG) and serum insulin (SI) values and the Matsuda insulin sensitivity index (Mat‐ISI) in young, healthy, overweight or obese and sedentary women.MethodsOn three separate days, 10 women (22.7 ± 4 years, BMI of 35.39 ± 5.36) reported for a fasted, venous blood draw. Participants consumed 5g of cellulose placebo or 5g of Cassia cinnamon bark. Three hours after the initial blood draw, the participants completed an OGTT by consuming a 75g glucose solution within 2 minutes. Venous blood draws were taken 30, 60, 90, and 120 minutes after OGTT to determine changes in BG and SI.ResultsThe maximum BG concentration following OGTT was significantly lower in the Cassia group, as compared to the placebo group (P = 0.025). The overall glucose response, glucose and insulin total area under the curve, and Mat‐ISI were not different between the two groups (P > 0.05).ConclusionsA 5g dose of Cassia cinnamon may reduce maximum post‐OGTT BG and improve glucose tolerance but does not have a significant impact on post‐OGTT insulin response in overweight or obese and sedentary women.