Low glycaemic index (GI) diet and gut hormones such as glucagon-like peptide 1 (GLP-1) and peptide YY (PYY) have been shown independently to reduce appetite. However, the direct relationship between a single meal of low or high GI and the levels of these hormones has not been studied. In this study we looked at the short term effects of a single low or high GI meal on plasma levels of GLP-1, PYY and insulin.
Kings College Londons research ethics committee approval was obtained for this study. Twelve healthy individuals with BMIs of 1825 kg/m2 took part in a randomized cross-over study. The subjects had an identical medium GI dinner in the evening prior to the study and fasted overnight. On the morning of study each subject consumed a single meal of low (46) or high (66) GI and subsequently had blood samples taken every 30 min for a total of 150 min. The entire process was repeated with the other test meal after a minimum two weeks wash-out. Plasma levels of GLP-1, PYY and insulin were measured on each blood sample.
The table below shows the post-prandial area under the curve (0150 min) for GLP-1, PYY and insulin. Our results demonstrate that there was a significantly higher post-prandial plasma level GLP-1 and lower level of insulin after the low GI breakfast compared to high GI (paired t-test, P value <0.005).
|Low GI||4839±1831||3461±563||10 088±4757|
|High GI||3865±1630||3448±631||16 245±7600|
Our data demonstrate that consumption of a single low GI meal results in higher levels of GLP-1. Previous studies showed the beneficial effect of low GI diet on suppressing appetite. GLP-1 is one of the most potent hormones in inducing satiety feeling. The present study may offer an insight into the physiological mechanism by which an low GI diet produces satiety.