The GI diet is based on how rapidly a particular carbohydrate (carb) turns into sugar. The GI says nothing about how much of that carbohydrate is in a serving of a particular food, and this is where the GL diet comes in.
GL stands for Glycemic Load. GL is a measurement that determines the impact of carbohydrate consumption. It is a ranking system for carbohydrate content in food portions based on their glycemic index (GI) and the portion size.
According to studies, if you follow a low GL diet for a short period of time (1-4 months) it will result in more weight loss or fat loss than if you would follow a high GL diet. The results of short-term studies show appetite regulation and weight loss. There need to be more studies on long-term GL diets, because there has not yet been found any real relevance to weight loss during a longer period of time.
If high GI food is consumed in small quantities, it will have the same effect on blood sugar as if you would eat larger quantities of food with a low GI. If you multiply the amount of carbohydrates in a food serving by the GI it will give you an idea of how much effect an actual portion of food has on blood sugar level.
Foods with low GL almost always have a low GI. Foods with a high GL range from very low to very high GI.
Example: A watermelon has a high GI, but since it contains a lot of water the GL is fairly low. The watermelon’s GI is about 72. One serving of 120 grams watermelon contains 6 grams carbohydrates.