Extended effects of evening meal carbohydrate-to-fat ratio on fasting and postprandial substrate metabolism

Abstract

High-fat and high-carbohydrate diets lead to insulin resistance, gastrointestinal adaptation, and high plasma triacylglycerol concentrations. It is unclear, however, how rapidly these changes occur. We sought to determine the effects of both high-fat and high-carbohydrate evening meals on parameters of insulin resistance, hypertriglyceridemia, and gastrointestinal hormones. Twelve healthy men were studied on 4 separate occasions. On 2 occasions, the subjects received a high-fat evening meal (62% of energy from fat) and on the other 2 occasions the subjects received a low-fat evening meal (16% of energy from fat). The morning after each meal the subjects were administered either an oral-fat-tolerance test or an oral-glucose-tolerance test. Plasma samples were analyzed for glucose, insulin, fatty acids, 3-hydroxybutyrate, triacylglycerol, pancreatic polypeptide, peptide YY, and cholecystokinin. Postchallenge data were analyzed by two-way analysis of variance with interaction and fasting concentrations analyzed by repeated-measures analysis of variance. Fasting plasma concentrations of triacylglycerol were significantly elevated 12 h after each evening meal, but fatty acid and 3-hydroxybutyrate concentrations were reduced. No effects on glucose or insulin concentrations were detected. The high-fat evening meals elevated plasma cholecystokinin concentrations, reduced fasting concentrations of pancreatic polypeptide, and had no significant effect on peptide YY concentrations. The ratio of fat to carbohydrate in the evening meal produced significant effects on plasma triacylglycerol and fatty acids during both the oral-fat-tolerance and oral-glucose-tolerance tests. The present study showed that the effects of high-fat and high-carbohydrate evening meals persist at least overnight and suggests that knowledge of recent dietary history is essential to the effective design of metabolic studies.