Concurrent ingestion of fat and reduction in starch content impairs carbohydrate tolerance to subsequent meals

We examined the effect of breakfasts of different macronutrient compositions on blood glucose and insulin levels after a standard lunch fed 4 h later. Fat-containing breakfasts were compared with a breakfast of equal carbohydrate and protein content and another with higher carbohydrate but equal calorie content. Concurrent ingestion of fat resulted in a large impairment of glucose tolerance following the standard lunch 4 h later. There was no significant difference in glucose and insulin if the fat eaten was butter or peanut butter. When the fat breakfast was compared with the isocaloric larger carbohydrate meal, the effect of fat on carbohydrate tolerance at lunch was even greater. Part of the reason for this additional difference is an improved glucose tolerance at lunch due to the higher carbohydrate content of the breakfast. Concurrent ingestion of fat and reduction of starch content have a persistent effect on carbohydrate tolerance to subsequent meals.