The Journal of Nutrition Nutrient Physiology, Metabolism, and Nutrient–Nutrient Interactions A High-Protein Breakfast Induces Greater Insulin and Glucose-Dependent Insulinotropic Peptide Responses to a Subsequent Lunch Meal

Background: The previous meal modulates the postprandial glycemic responses to a subsequent meal; this is termed the second-meal phenomenon. Objective: This study examined the effects of high-protein vs. high-carbohydrate breakfast meals on the metabolic and incretin responses after the breakfast and lunch meals. Methods: Twelve type 2 diabetic men and women [age: 21–55 y; body mass index (BMI): 30–40 kg/m2] completed two 7-d breakfast conditions consisting of 500-kcal breakfast meals as protein (35 % protein/45 % carbohydrate) or carbohydrate (15% protein/65 % carbohydrate). On day 7, subjects completed an 8-h testing day. After an overnight fast, the subjects consumed their respective breakfast followed by a standard 500-kcal high-carbohydrate lunch meal 4 h later. Blood samples were taken throughout the day for assessment of 4-h postbreakfast and 4-h postlunch total area under the curve (AUC) for glucose, insulin, C-peptide, glucagon, glucose-dependent insulinotropic peptide (GIP), and glucagon-like peptide 1 (GLP-1). Results: Postbreakfast glucose and GIP AUCs were lower after the protein (17%) vs. after the carbohydrate (23%) condition (P < 0.05), whereas postbreakfast insulin, C-peptide, glucagon, and GLP-1 AUCs were not different between conditions. A protein-rich breakfast may reduce the consequences of hyperglycemia in this population. Postlunch insulin, C-peptide, and GIP AUCs were greater after the protein condition vs. after the carbohydrate condition (second-mea