They are, in fact, very similar. The aim is the same - to keep your blood sugar level stable. But using GL to control blood sugar, rather than carbohydrate restriction, is a safer, more scientific approach than that advocated by many low carb diets.
There is no doubt that low carb diets work. The millions who have lost weight that way will attest to that. But most respectable nutritionists reject the ideas of Dr Atkins as to how the diet works. No one has been able to show that calories from carbohydrates act differently to calories from any other source. Weight gain or loss is still a question of calories in versus calories out.
The current scientific view is that stable blood sugar level depresses the appetite and you simply eat less. This is good news for dieters because it means that you can get the same weight loss effect with low GL diets as you do with low carb diets. The difference being that you are able to eat a great deal more foods, because you can eat good carbs, than you would with low carb diets.
Is the GL rating the same as the Net Effective Carbs?
Both the GL rating and the Net Effective Carb count on a food product are measured in grams. But the GL rating is arrived at by measuring the effect that a food has on blood sugar level whereas Net Effective Carbs are calculated from the ingredients. You can show mathematically that the Net Effective Carb count is an attempt to calculate the GL of a food product. The problem is that it is a crude approximation, which divides carbohydrates into everything or nothing categories and takes no account of the interaction between different food components.
Recently, to overcome this sort of criticism, Atkins Nutritionals has introduced a blood sugar measurement just like glycemic load to categorise their products. It's called The Net Atkins Count and is based on comparing their products to the glycemic effect of white bread. Since white bread has a GI of 70 you can convert Net Atkins Count to GL by multiplying by 0.7. So, for example, a product with a Net Atkins Count of 3g will have a GL of 2g. This is a welcome move by the Atkins Organization which will benefit millions of low carb dieters by introducing them to the concept of glycemic load.