5.1 The role of the glycaemic index

The interactive figure shows a line graph with blood glucose levels on the vertical Y axis and Time/hours (up to 2 hours) on the horizontal X axis. The graph shows a red line for High GI food and a yellow line for Low GI food. The red High GI line rapidly rises and peaks at around 30 minutes and then drops rapidly. The yellow Low GI line slowly rises towards around 45 minutes and then slowly drops towards 2 hours. When clicking on the High GI and Low GI lines the following explanations are revealed:

High GI -The red line on the graph shows that when high GI foods are eaten, they are rapidly digested and absorbed into the bloodstream. This in turn causes rapid changes in the individual’s energy levels, initially feeling full of energy as the glucose floods the bloodstream, then feeling tired and lethargic once it has been removed from the bloodstream. The consumption of high GI foods post-exercise can be important to rapidly replenish energy stores.

Low GI - The yellow line on the graph shows that when low GI foods are eaten, they are slowly digested and absorbed into the bloodstream. Low and moderate GI foods lead to a gradual rise in blood sugar level. Having stable blood glucose levels makes us feel less hungry and more energised over the length of the day, rather than experiencing energy peaks and troughs. The consumption of low GI foods is therefore beneficial for appetite and weight management and before exercise to promote sustained energy release.