The ideal foods are predominately carbohydrate (CHO) based and of a low glycaemic index (Gl)

The Gl is a tool that has been developed to measure the response in blood sugar levels to certain foods.

The index is derived by comparing all foods to a reference standard, normally 50g CHO from white bread or 50g glucose. A person is fasted overnight and then fed the reference food.

The blood glucose response is measured and this is then used as a reference.

The same procedure is then carried out for other foods and the response is compared to the reference foods response. Based on this response all foods are given a Gl of up to 100 (some foods have a larger number as they produce a higher response).

The higher the GI number, the quicker the blood sugar rises.

With white bread the peak occurs after about 30 minutes and then drops away over the next 60 to 90 minutes. Lower Gl foods however, produce a more flattened response but remain elevated for a lot longer, thus providing a steadier supply of glucose to the body over a longer period of time.

Because the blood sugar remains slightly more elevated for longer, the hunger response is dampened and therefore you will tend to want to eat less.

Low Gl foods also have another benefit, in that they possess what is known as a secondary meal response (Bjorck et al, 2000 - British Journal of Nutrition).

This means that they have a knock-on effect on the next meal consumed. If your next meal were to be predominately high Gl CHO, because you have previously consumed a low Gl breakfast, the Gl of the second meal will be dragged down; thus flattening what would otherwise have been a sharp peak in blood glucose levels.