Several readers have written asking for an explanation of the glycaemic index (GI). With the festive season in full swing and a diet for most of us consisting of plenty of alcohol and rich, sugary, refined carbohydrates, there's no time like now to consider the index. Even if you do over-indulge, once the principles of the index are understood, the damage can be limited.
Carbohydrates are an essential source of fuel for the body, especially the brain, which is why they are always present in the bloodstream as blood sugar. But not all carbohydrates were created equal, there are good ones and bad ones.
The bad - alcohol, sugar, foods containing it, and those based on white rice or white flour - cause the level of glycaemia or sugar in the blood to become too high too quickly.
When this happens the brain sends an emergency signal for help to the pancreas. This organ secretes the hormone insulin, one of whose many roles is to keep blood sugar at a safe level.
The excess is stored in the liver and muscles and insulin plays a key role in both the burning and storage of fat too. Unfortunately, the surge of insulin drives levels too low, causing hypoglycaemia, or low blood sugar, making the person suddenly hungry again. This is the sugar 'hit' followed by the slump after a sugary snack. It also explains rebound hunger after a Chinese meal with white rice. Insulin is the hunger hormone and is also stimulated by alcohol (hence the munchies), coffee and monosodium glutamate (MSG).
Low blood sugar leads to cravings for sugary, fatty food, for an instant sugar boost, which makes you fat.
Insulin is also called the fattening hormone. The glycaemic potential of each carbohydrate is measured by the glycaemic index, topped by glucose (sugar) at 100. The higher the GI, the greater a carbohydrates potential to raise blood sugar levels and stimulate insulin production.
