The study of metabolic improvement by nutritional intervention controlling endogenous GIP (Mini Egg study): a randomized, cross-over study

Background: Given the major role of glucose-dependent insulinotropic polypeptide (GIP) in the regulation of adiposity, this study examined the effects induced by a diet based on the Japanese tradition (SMART WASHOKU) on the visceral fat area (VFA) and GIP secretions. Methods: Overweight/obese men (n = 21; mean age, 41.0 +/- 9.0 years; mean BMI, 25.2 +/- 2.0 kg/m(2)) without diabetes were placed on either a SMART WASHOKU or control meal for 2 weeks, in a randomized, cross-over setup with a four-week washout period. Results: For the meal tolerance test, blood samples were collected at 0, 30, 60, 120, 180, and 240 min post-meal, followed by measuring blood glucose, insulin, GIP, and glucagon-like peptide-1 (GLP-1) levels. Relative to a control meal, SMART WASHOKU meal yielded significantly lower plasma postprandial GIP concentrations (AUC: 700.0 +/- 208.0 vs. 1117.0 +/- 351.4 pmol/L 4 h, P < 0.05); however, between meals, there was no significant difference in the levels of GLP-1, peptide YY, and ghrelin. Compared to the control meal, SMART WASHOKU intervention significantly reduced VFA and the levels of LDL-cholesterol, triglyceride, and HbA1c after the chronic meal intervention. Conclusions: In conclusion, a SMART WASHOKU meal may decrease VFA and improve metabolic parameters in overweight/obese men, possibly via suppressing GIP secretion.