Substrate, hormone, and temperature responses in males and females to a common breakfast

To evaluate the response to a mixed meal we studied oral temperature, metabolite, and hormonal responses to a common American breakfast containing 11 kcal/kg body weight (carbohydrate 43%, fat 42%, and protein 15%) in 12 normal volunteers (6 males and 6 females). There was a significant rise in oral temperature during the postcibal period. This change in oral temperature did not depend upon food consumption in males but was meal-dependent in females. Food ingestion caused increases in the peripheral circulating concentrations of glucose, lactate, pyruvate, and amino acids and reciprocal decreases in the concentrations of free fatty acids, glycerol, and urea nitrogen. Acetoacetate and beta-hydroxybutyrate decreased during the postcibal period but the changes were not statistically significant. Although peripheral venous serum insulin and plasma glucagon concentrations were indistinguishable between the sexes, males had higher concentrations of plasma triglycerides, plasma amino acids, and serum urea nitrogen. Peripheral venous plasma somatostatin and secretin remained unchanged, but pancreatic polypeptide hormone showed a large biphasic response to the meal. After breakfast the blood glucose concentration tended to be greater in males than in females and this difference was significant at 60 and 120 min postcibal. Furthermore, every female had a 120 min postcibal glucose concentration that was lower than her basal fasting glucose concentration. This suggests that postcibal glucose concentrations should be related to gender in making the diagnosis of carbohydrate intolerance or reactive hypoglycemia.