Glycemic Index and Glycemic Load

Consumption of high glycemic load foods has been associated with higher risk of diabetes, coronary artery disease and cancers including breast cancer.
Low glycemic load foods are important for weight control.
It is helpful to know the glycemic load and glycemic indices of foods when we have such wide variety of foods available to us with many of them contributing to obesity.

Glycemic Index: (GI)
Glycemic index is the effect of a food on blood glucose compared to a reference food (Glucose or white bread). Glycemic index of the reference food is considered 100.
In other words, glycemic index is derived by measuring the rise in the blood sugar caused by carbohydrate in a particular food and comparing it with the rise caused by same amount of carbohydrate in reference food (glucose or white bread).
Glycemic index is not something we can calculate ourselves. It is measured by the nutrition scientists and has been determined for most of the commonly available foods.

Glycemic index is classified into high, medium and low.
High Glycemic index is more than 70
Medium Glycemic index is 56 - 69
Low Glycemic index is 55 or less

Glycemic index depends on a number of factors such as rate of absorption of a food, fiber content, type of carbohydrate, food processing etc. Usually whole grains and high fiber foods have low glycemic index and refined or processed foods will have high glycemic index. For example lentils have glycemic index of 29, Orange juice has 50 and Gatorade has a glycemic index of 78.
There are exceptions, for example even a high fiber whole grain bread depending upon it’s processing may have a high glycemic index.

Limitation of glycemic index:
Glycemic index does not take into account the amount of carbohydrate in a food. For example green peas and corn tortilla have approximately similar glycemic index (Green peas = 51 and corn tortilla = 52). However rise in the blood sugar is much higher with corn tortilla compared to green peas. This is because there is higher net carbohydrate in corn tortilla compared to same amount of green peas.

Glycemic Load (GL):
Glycemic load is more useful than glycemic index because it also includes the amount of carbohydrate. It is calculated by multiplying the net carbohydrate (in grams) with the Glycemic index and dividing it by 100.
Glycemic Load = Net carbohydrate (gms) x Glycemic index/100
In other words, Glycemic index takes into account both quality (GI) and quantity of carbohydrate
What is considered a high glycemic load for a food? Here is the classification:
High Glycemic load = 20 or more
Medium Glycemic load = 11-19
Low Glycemic load = 10 or less

Important consideration:

When trying to lose weight or when when choosing a diet for healthy living attention should not be focussed on merely one factor such as glycemic load or glycemic index.
Even low glycemic index foods can be unhealthy due to high degree of processing and addition of artificial substances and preservatives or can be high in fat or total calories.

In general if one avoids processed food, eats mainly meals cooked at home from scratch with whole and natural ingredients there is not much need to follow glycemic load obsessively. Most meals prepared with whole, unprocessed natural ingredients have low glycemic index. Even then, having the knowledge does not hurt. With the food abundance we have around us we may find ourselves overindulging in that one natural, unprocessed, wholesome delight that happens to have quite high glycemic index and glycemic load.