Glycemic Index vs Glycemic Load
The Glycemic Index is a very useful way to determine how quickly the carbohydrate (sugar) in a food will be absorbed into the blood stream, but the Glycemic Load is an even better measure of determining the insulin response and therefore how fattening a food is.
The Glycemic Index is a list of foods that compares how quickly 50 grams of carbohydrate within the food will raise your blood sugar as compared to 50 grams of sugar alone. To calculate the Glycemic Index of a food, scientists measure out the quantity of a particular food needed to obtain 50 grams of carbohydrate, they feed that quantity of food to test subjects, and measure the blood sugar response.
They then compare the blood sugar response of the food with the response from 50 grams of straight sugar, which is given a GI value of 100. For example, four slices of white bread has about 50 grams of carbohydrate, and gives a blood-sugar response of roughly 70 to 73% that of straight sugar, and therefore has a GI of 73, if we take the high number.
The more quickly the sugar is dumped into the blood stream, the higher the insulin response, the greater the fat storage and chance for disease. The closer the number is to 100, the closer the food acts like sugar in the body and the more fattening and the more destructive it is. A GI value of 55 or less is considered low.
The problem with the Glycemic Index is that although it looks at how quickly the sugar that is in the food is put into the blood stream, it does not consider serving size at all. One might have to eat a whole lot of some foods to get that 50 grams of carbohydrate in order to figure out the GI.
For example, it takes 1 1/2 pounds of carrots to get the 50 grams of carbs upon which the GI is based. Not many people eat 1 1/2 pounds of carrots at one sitting however. Glycemic Load takes into account serving size, which therefore provides an even more useful number.
Glycemic Load is calculated by taking the number of grams of carbohydrate in the serving of the food being consumed, multiplying that with the GI value, and then dividing by 100. I like this boiled potato example, given by Bill Campbell, PhD, CSCS.
“For example, a boiled potato has a glycemic index of 101 and a Mars® candy bar has a glycemic index of 65. However, the average serving size of a baked potato is about 150 grams (5.3 oz) and contains 17 grams of carbohydrate. Conversely, a Mars® candy bar serving size is only 60 grams (2.1 oz) but contains 40 grams of carbohydrate. The boiled potato has a glycemic load of 17, while the Mars bar is 26. Thus, even though the potato has a higher glycemic index, the Mars® candy bar has a greater effect on blood glucose than the potato even though the size of the Mars® candy bar is less than half that of the potato.”
A Glycemic Load of under 10 is considered low and would make for the best food choices, particularly if they are unprocessed. Click here for a list of foods and their Glycemic Index and Load.
Note how almost all the grains and cereals, even ones considered healthy like steel-cut oats, have a high glycemic load. For those that fatten up easily or are at higher risk for developing type 2 diabetes, heart disease or cancer, eating pastured steak or eggs along with lots of veggies would therefore make for a healthier breakfast choice.
These lists contain the foods specified alone. One can also greatly affect the blood-sugar/insulin response by eating the food with protein and/or fat which blunts the blood sugar response. Putting butter on a slice of bread or cream on porridge makes it less fattening than having the bread or porridge alone.