Effect of a High Protein Diet at Breakfast on Postprandial Glucose Level at Dinner Time in Healthy Adults

This study aimed to examine the effect of high protein breakfast diet with or without lunch on the postprandial glucose level during the day. A randomized, crossover design that recruited 12 healthy young participants (three men and nine women) was performed and four trials (normal breakfast + skipped lunch, high protein breakfast + skipped lunch, normal breakfast + lunch, and high protein breakfast + lunch) were conducted in two weeks. During each trial, breakfast, lunch, and dinner on the trial day, and dinner before the trial day, were provided as test meals, and the meal timing was fixed. Continuous glucose monitoring (CGM) was used to assess the blood glucose level during the whole experiment. Incremental area under the curve (iAUC) of the postprandial glucose level was calculated. The results suggested that compared with normal breakfast, high protein breakfast suppressed the 3 h iAUC of postprandial glucose level after breakfast (p < 0.05 or p < 0.0001) and 1.5 h iAUC after lunch (p < 0.01). During lunch, high protein breakfast diet suppressed the dinner and overall day postprandial glucose level (p < 0.05 vs. normal breakfast), but no significant difference was observed when skipping lunch. Our findings indicate that high protein breakfast could suppress the breakfast postprandial glucose level, as well as following lunch and dinner, but this effect on dinner was attenuated when skipping lunch.