Left: plasma glucose response to the ad libitum meal consumed 30 min after the preload (Mean ± SEM). Right: plasma glucose response area under the curve (AUC) (Mean + SEM). Bars with different superscripts are significantly different at P < 0.05. The response after the maltodextrin preload was not included in the analysis since it is 100% carbohydrate and resulted in a pre-meal baseline value that was much higher and incomparable to the protein and control values. Plasma glucose response to the ad libitum meal was significantly lower when whey protein was consumed as a preload compared to the other preloads (P < 0.001).