What is the difference between the glycemic index and glycemic load?

I know what you’re thinking. You understand how to balance your carbohydrates, proteins and fats and you are beginning to understand the glycemic index. You then hear a friend mention how important it is to know the glycemic load of the foods you eat as well. Now you’re confused. What’s the difference between a particular food’s glycemic index and its glycemic load? Let’s clear that up.

Both the glycemic index and the glycemic load rankings refer to carbohydrates. When carbohydrates are digested, sugar enters the bloodstream. The glycemic index ranks how quickly sugar (glucose) enters the bloodstream after a particular carbohydrate is eaten.
Here is why it is significant:

• If blood sugar rises too quickly, your brain signals your body to secrete a greater amount of insulin.

• Insulin helps bring sugar out of the bloodstream, primarily by converting the excess sugar into fat and storing it in your body.

• A greater rate of increase in blood sugar leads to a greater insulin release, more storage of fat and then a drastic lowering of blood sugar levels. This is what leads to an energy rush followed by lethargy and hunger after eating a candy bar.

• This is significant because excess insulin secretion can result in various ill health effects such as fatigue, weight gain and, eventually, type 2 diabetes.

For ranking purposes, the glycemic index is divided into three categories: low, medium and high. Food is categorized from low to high on a scale of 0 to 100, depending on its effect on blood sugar levels. Foods that are lowest on the glycemic index have the slowest rate of glucose entry into the bloodstream, and therefore have the lowest insulin response. The categories are:

• Low (up to 55)
• Medium (56 to 70)
• High (over 70)

Fibre, protein and fat all slow down the entry of glucose from a particular food into the bloodstream. Most vegetables, beans and whole grains are full of fibre, which is reflected in their lower glycemic index rating. For example:

• Green peas 48
• All-bran 38

However, processed foods (e.g., white flour) usually contain little to no fibre and therefore tend to have a higher glycemic index rating. For example:

• Strawberry cupcake 73
• White bread 73

One limitation of the glycemic index is that it does not take into account how much sugar a particular food contains — it is only a reflection of how quickly the sugar is absorbed. For example, the sugar in carrots is readily absorbed into the bloodstream and they are therefore ranked high on the glycemic index (74). This has given carrots some undeserved bad press. Many people decide to avoid carrots because they assume that because they are high on the glycemic index they will cause them to gain weight. This is where the glycemic load of a particular food becomes very useful.

The glycemic load takes into account not only how quickly a certain food is converted into sugar in the body but also how much sugar (carbohydrate) a particular food contains.
The glycemic load categories are:

• Low (10 or less)
• Medium (11 to 19)
• High (20)

Your body’s glycemic response depends on both the type of food eaten and the amount of carbohydrate (sugar) calories consumed. The more concentrated a carbohydrate is, the more sugar it dumps into your bloodstream. Although all of the sugar that is in the carrots is absorbed into the bloodstream quickly (high glycemic index), there is not a lot of sugar to begin with (low glycemic load). As you can imagine, the same amount of dense white pasta would have both a high glycemic index and a high glycemic load.

This explains why even though carrots are high on the glycemic index, you are not likely to gain weight eating them.