In this article I want to explain how the glycemic index, glycemic load and insulin index work.
The glycemic index and glycemic load are variables measured in carbohydrate foods, that evaluate how much they raise blood glucose levels. The insulin index measures the effect on blood insulin levels.
These are often used by diabetic patients to control blood glucose levels.
Personally I think that diabetics would do better by skipping high carbohydrate foods altogether and choose a low-carb, ketogenic diet and Steve Cooksey the Diabetes Warrior is a living example of that.
The Glycemic Index
The glycemic index is simply a measurement of how quickly a carbohydrate food raises blood sugar, compared to the same amount of glucose.
The amount measured is the area under the “two hour curve” when blood glucose is measured for two hours after a meal. The bigger the area, the faster that particular carbohydrate raises blood sugar.
If a food has a high glycemic index (GI), it means that the food is digested and turned into blood sugar quickly. If it has a low GI, it happens slowly.
The way the scale works, is that 50 grams of glucose is assigned a GI score of 100. Then other foods are measured and compared to glucose. For example a food that raises blood sugar 40% as much as glucose is assigned a score of 40.
Many things can affect the glycemic index of a food. For example, it will be lower if consumed with fat or fiber. It will also depend on the individual, and the ripeness and cooking method of the food.
Foods with a lower glycemic index (fruit, whole grains) tend to be healthier than foods with a higher glycemic index (candy, white bread), and eating foods with a low GI is correlated with improved health. This has a lot of exceptions though.
The Glycemic Index Scale:
- Low: 55 or less
- Medium: 56-69
- High: 70 or higher
Check out this database if you want to find the glycemic index or glycemic load of particular foods.
The Glycemic Load
Another system known as the Glycemic Load (GL) is much better for predicting blood glucose levels after meals, because it also incorporates serving sizes.
It is simple to figure out the Glycemic Load if you already know the GI of a food and its carbohydrate content. You multiply the Glycemic Index with the amount of carbohydrate in grams, and divide by 100.
Glycemic Load (GL) = Glycemic Index (GI) * Carbs in grams / 100
For example apples with a GI of 40 and a carb count of 16 grams: GL = (40 * 16) / 100 = 6.4
Therefore foods with a high GI and/or high carb content have a higher glycemic load, while foods with a low GI and/or low carb content have a lower glycemic load.
The Glycemic Load Scale:
- Low: 10 or less
- Medium: 11-19
- High: 20 or higher
The Insulin Index
The Insulin Index measures blood levels of insulin after meals.
These levels are usually correlated with glucose levels, with some exceptions. Some protein containing foods such as beef can cause a higher insulin response than certain carbohydrate containing foods.
The Insulin Index measures the insulin response to various foods, relative to the insulin response to white bread, which is assigned a score of 100.
A food that raises insulin more than white bread has a score over 100, while a food that raises insulin less than white bread has less than hundred.
Some examples: porridge with an insulin index of 40, much less than white bread. Potatoes with 121, higher than white bread and beef with a score of 51 which is less than white bread but higher than porridge.
Hey Kris!
Great stuff: informative, and sure useful to the dieter! You gonna be a Nutritional Scientist?
Do you know Dr.Lonnie Lowery? He’s a Bodybuilder AND a Professor of nutrition, so you get the scientific lowdown on performance based nutritional research. I have personally learned a fair bit from him (he writes a lot on T-Nation for example).
Have a Good One,
Mark
Hey Mark, thanks for commenting.
I’m not really sure what I’ll do when I get my medical degree, but something related to nutrition and metabolism is definitely an option. Haven’t heard of Dr. Lowery but I’ll look him up :)
Sure man!
Dr.Lowery is really good, my Temporal Synergy concept was inspired, you might say, by his temporal nutrition work. Here’s his site, and like I said you’ll find him on tnation under temporal nutrition I think.
Mark
P.S.
Of course no offense if you wanna throw out the outgoing links, but it’s good resources for many!
Thanks, I’ll have a look at it :)
What would you recommend as good pre-workout and post-workout foods for a young competitive swimmer. My 11-yr-old son is nearing 5’7″ and weighs 107lb, so quite lean in physique. My concern is that he not burn muscle post-workout.
Currently, he prefers a PB&J sandwich on white bread 15 minutes before hitting the water for a practice that runs 1.5 to 2 hrs – it seems to work for him and he’s neither nauseous nor hungry while in the water.
After practice, it’s more difficult to get high GI/GL foods in him in addition to his whey isolate protein shake he takes about 30 minutes after practice. Then there’s an actual meal about 1-1.5 hrs later..
Any tips you can pass on to help with glycogen replenishment would be much appreciated. P.S. he’s lactose-intolerant, and not a big fan of super-sweet foods.
Well, normally I wouldn’t be too fond of eating white bread but since your son is a competitive swimmer and seems to tolerate it well, then I don’t see a problem as long as he eats healthy and nutritious foods the rest of the day.
Regarding glycogen replenishment, bananas are great post-workout and very easy to get down. There are carbohydrate supplements with simple sugars in them that some people like to mix in with whey protein, but I’m not too fond of those. I’d say the bananas are a good bet.
I’m really no expert on exercise nutrition though, perhaps you should ask your son’s trainer what he thinks. Hope that helps.
Hey Kris, mind if I take this one?
Alright the PB&J Sandwich is about the worst thing i the world he could have, no matter how he feels on it.
A Good PWO is the best option for him IMMEDIATELY after the training, then the meal 1.5 -2h later.
The Pre-Wo Meal should be Low G.I. Carbs like wild rice or beans with a good source of protein, and that should be at least 1.5-2 hours away from practice (before).
PWO Formula: For this weight? 10 gram L-Glutamine, 20 Whey, 30 carbs, like maltodextrine, even a Banana would do here.
TRUST Mark! ;-)
Kris/Mark -
Thanks for the feedback.
I too was a little shocked by the PB&J pre-workout snack, but since it seemed to do him, I thought what the heck. (Before the PB&J, the pre-wo snack was a Simply Bar but he didn’t like the taste and he would run out of steam half-way though practice.) He does prefer ancient grain breads over white so would this be a better option Pre-WO, eaten 1.5 hrs ahead of practice? Easy on the jam, of course. We are fortunate that he does like healthier foods, so we don’t have the nutrition fight on our hands that many parents have, but he is still a kid, who will be eating on the go, so we have to contend with ease of transport and a kid palate.
Post-WO, he used to have a banana but we were told bananas take too long for the body to use (moderate glycemic index, with low glycemic load). I would have thought something with a higher glycemic index/load. He is already taking the protein shake so I am not keen on additional supplements, would rather go with a whole food source.
Kris, may I?
The ancient thing will definitely be better than wheat, that’s about the worst out there as far as grains … If it has to be bread I’d say spelt or barley, even oats are WAY better. And yeah, 1.5-2 hours before practice.
That way it won’t weigh him down, and the energy will be readily available by that time.
No bananas are really fine, but here’a a list of other fast carb/high G.I. fruit for post workout:
Mango, Pineapple, Guava, Kiwi, Bananas, Grapes, Figs, Dates (grapejuice and co are OK here too)
P.S.
If he has to have the white bread, the only time it’s applicable would be as a post workout carb source. Banana, Sandwich … it’s OK after the training, because then you want the fast carbs, like you said. And boy IS white bread fast? Oh boy oh boy! ;-) But if you’re concerned about recovery and lean mass, please don’t forget the glutamine, that’s the boss as far as all that.
Good Luck,
Mark
Thanks, Mark! You too, Kris! It looks like we’re good for both pre- and post-workout. The protein powder for his shake (Bio-X All-Natural Whey Isolate, sweetened with stevia) contains the l-glutamine you speak of, and kiddo loves fruit leathers (Sun Rype Fruit Source is 100% fruit), so I think we’re now fine post-workout. And you’ve got us on the right path for pre-workout. Thanks for the invaluable guidance. :)
My pleasure! ;-)
But remember, Glutamine:10 gram minimum. It’s great for recovery, the brain, the immune system, growth hormone production and good for the long tract. Awesome stuff (pure L-Glutamine powder).
Mark
A larger online database of glycemic index and glycemic load: http://health-diet.us/gid/ . There are nearly 4,000 foods in this database.
Thank you, Henry :)