Glycemic index and glycemic load

Glycemic index or GI ranks carbohydrates according to their effect on our blood glucose levels.The glycemic index (GI) is a numerical system of measuring how much of a rise in circulating blood sugar a carbohydrate triggers—the higher the number, the greater the blood sugar response. So a low GI food will cause a small rise, while a high GI food will trigger a dramatic spike. Many packaged food products list the glycemic index, although it is not required. For reference, use this glycemic index chart to interpret the numbers:

  • Low (good) glycemic index levels: 55 or less
  • Medium glycemic index levels: 56–69
  • High (bad) glycemic index levels: 70 or higher
  • Choosing low GI carbs – the ones that produce only small fluctuations in our blood glucose and insulin levels – is the secret to long-term health reducing your risk of heart disease and diabetes and is the key to sustainable weight loss.

Researchers have spent years debating what makes blood glucose levels too high. Potential culprits have included sugar, carbohydrates in general, simple carbs, starches, and more. The glycemic index is one attempt to measure each individual food’s effect on blood glucose levels.

High glycemic index foods include many carbohydrates such as these:

  • Bread
  • Pasta
  • Rice
  • Cereal
  • Baked goods

Low glycemic index foods generally have less of an impact on blood glucose levels. People who eat a lot of low glycemic index foods tend to have lower total body fat levels.

Low glycemic index foods include these:

  • Fruits
  • Vegetables
  • Whole grains
  • Legumes

Unprocessed foods tend to have lower glycemic indices than refined foods. Factors That Alter the Glycemic Index

Knowing whether a particular food has a low or high glycemic index is a great start. However, several factors can change a particular food’s glycemic index:

  • The other foods eaten at the same time
  • Other components of a food, such as the amount of protein or fat
  • How the food was prepared
  • Your own body’s reaction to the food

Many people have found the glycemic index to be a useful tool for controlling blood glucose levels or for losing weight. If you want to try the glycemic index as well, talk to your doctor. He or she may refer you to a dietitian, who can give you specific steps to follow as well as tips to make using the glycemic index easier.

The glycemic load (GL) is a relatively new way to assess the impact of carbohydrate consumption that takes the glycemic index into account, but gives a fuller picture than does glycemic index alone. A GI value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn’t tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food’s effect on blood sugar. That is where glycemic load comes in. The carbohydrate in watermelon, for example, has a high GI. But there isn’t a lot of it, so watermelon’s glycemic load is relatively low.

  • A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.

Foods that have a low GL almost always have a low GI.

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