The present study aims mainly at measuring, in normal rats, the GLP-1 response to oral intake of an olive oil-enriched diet (OO), and at assessing the long-term effects of such a diet on the GLP-1 content of the intestinal tract, as well as the plasma D-glucose, insulin, and GLP-1 pattern during an oral glucose tolerance test. In meal-trained rats, the mean increment in plasma GLP-1 concentration at min 10 and 20 was 1.39 +/- 0.23 ng/mL higher (p < 0.001) in the rats given access to the OO diet rather than control diet. Relative to the initial value (d 0), the gain in body weight at d 50 was also higher in the animals fed the OO rather than control diet. At d 50, the GLP-1 content of the jejunum, ileum, colon, and cecum were not significantly different in the two groups of rats. At d 19 and 36, the increment in both plasma insulin concentration and paired ratio between plasma insulin and D-glucose concentrations were again higher, during an oral glucose tolerance test conducted in overnight fasted animals, in the rats otherwise fed the OO, as distinct from control, diet. The intake of an olive oil-enriched diet thus increases, in normal rats, GLP-1 release, this coinciding during long-term exposure to the OO diet with higher body weight gain, increased secretory response of insulin-producing cells to oral glucose administration, and, after 36 d, improved glucose tolerance.