Short-term low carbohydrate/high-fat diet intake increases postprandial plasma glucose and glucagon-like peptide-1 levels during an oral glucose tolerance test in healthy men

BACKGROUND/OBJECTIVES: Postprandial hyperglycemia increases the risks of development of type 2 diabetes and cardiovascular diseases. The purpose of this study was to determine whether a 3-day low-carbohydrate/high-fat diet (LC/HFD) alters postprandial plasma glucose and incretin levels during oral glucose tolerance test (OGTT) in healthy men. SUBJECTS/METHODS: Nine healthy young men (age (mean +/- s.e.), 27 +/- 1 years; body mass index, 22 +/- 1 kg/m(2)) consumed either a normal diet (ND: energy from similar to 22% fat) or a LC/HFD (energy from similar to 69% fat) for 3 days each. The total energy intake from each diet was similar. An OGTT was performed after each 3-day dietary intervention. Postprandial plasma glucose, insulin, free fatty acid and glucagon-like peptide-1 (GLP-1) levels were determined at rest and during the OGTT. RESULTS: Plasma glucose levels and incremental area under the curve during the OGTT were significantly higher in the LC/HFD trial than in the ND trial (P = 0.024). In addition, increase in GLP-1 levels was significantly higher in the LC/HFD trial than in the ND trial (P = 0.025). The first-phase insulin secretion indexes were significantly lower in the LC/HFD trial than in the ND trial (P < 0.041). CONCLUSIONS: These results demonstrate that even short-term LC/HFD increased postprandial plasma glucose and GLP-1 levels in healthy young men. A decrease in first-phase insulin secretion may partially contribute to the short-term LC/HFD-induced increase in postprandial plasma glucose levels.