Low-GI and Low-GL

The title of this one might throw you, as I’m sure some of you recognize “GI” as “gastrointestinal” and, in particular, disorders related to the gastrointestinal tract (Known of, no doubt, because of the terrible diets we Americans lead). Either that, or “GI” as in…um, military guy. Well; I’d like to introduce you to a new meaning of “GI,” if you don’t already know it: Glycemic Index. Glycemic Index and its big brother Glycemic Load (Just GI x percentage, by weight, of carbohydrates) are suggested as indicators of the healthfulness of whatever particular carbohydrate you’re consuming. Glycemic index works by measuring the effects of carbohydrates, which are more-than-plentiful in the American diet, on blood sugar levels. Blood glucose, especially after meals, has been found to be a determining factor in the incidence of diabetes, atherosclerosis, and coronary heart disease. So, therefore, the glycemic index scale was created to measure post-eating blood glucose levels based on the ingestion of glucose itself. The effect of glucose ingestion on blood glucose levels is given a GI value of 100, and all other carbohydrate foods are measured against that standard. For example, an apple has a GI of about 40 (again assuming glucose= 100 GI) and a GL (glycemic load) of 6; both of these are low values on their respective glycemic index and glycemic load scales as those considered low-GI foods are below 55 on the GI scale and low-GL foods are below 10.

So what’s the difference between glycemic load and glycemic index?

A lot of low-GI foods are really great for you and will thus help in weight loss; this includes most fruits and vegetables, after all…but what if a fruit is high-GI? Fruits are generally considered universally healthy, but high-GI fruits do exist. Take, for instance, a watermelon; this staple “summertime fun” fruit has a GI of 72, putting it in “high” territory. Watermelon is a good natural source of vitamin A and potassium (and duh, it tastes great!), but does this high-GI value negate all that goodness and place watermelons on the “No-no” list? That’s where GL, or glycemic load, comes in: glycemic load compensates for the actual carbohydrate amount in food. Sure, the sugars in watermelon boost its GI up; but the fact is, there are only 6 grams of carbohydrate to the 120 gram serving size. So, here’s the math in ascertaining the GL (keeping in mind that a GL below 10 is considered low): 120 grams of watermelon at 72 GI would be (72×6 (the number of total carbs) divided by 100). We come up with a GL of 4.32, which is obviously very low. The sugars in watermelon will still metabolize quickly, but you’d have to eat over double that portion to even get in the intermediate GL (10-20) range and have a significant spike in blood sugar. By realizing the importance of carbohydrate content, it’s easy to surmise that choices based on GI should include more carbohydrate-rich, man-made foods like breads, and choices based on GL should include more “natural” foods like fruits and vegetables.

Limitations of GI and GL measurements

This is where I ruffle the feathers of glycemic diet plan enthusiasts. To start with, there are a host of “trickster” foods in terms of GI; fructose being a prime example. Fructose, which is an equal part with glucose in sucrose (all right, I’ll stop saying words ending with -ose; sucrose is table sugar), is GI’s version of “a wolf in sheep’s clothing.” Fructose has a spindly GI of around 10, and its GL is about 1; so, it must be good…right? I guess I won’t floor you when I bold-type a resounding WRONG (If, by the way, I did, please send pictures of your shock for entry in my “Oblivious to Foreshadowing Surprised Face Contest” P.O. Box 3-okay, this joke’s over). The problem with fructose is that it has been found to be directly responsible itself for causing maladies of the heart, much like its high-GI carbohydrate pals. Many people, in blind belief of the glycemic diet plan, have turned to low-calorie, fructose-infused sweeteners like agave nectar as a result of their newly-found “Low-GI” knowledge. This is the case for most of the other artificial sweeteners (read: carcinogens) like aspartame and sucralose, as well. Additionally, alternative research has shown that the very GI values attributed to certain foods in prior lab tests did not hold up to scrutiny in a less lab-centric environment i.e. an environment that was monitored well, but where subjects were allowed to essentially “pig out” at their leisure, both with mixed-carbohydrate and single carbohydrate meals. A follow-up response to naysayers of said study argues (successfully, in my vainglorious view) that glycemic index is a property of a food, not a measure of the response in any given person; thusly, that it cannot be viewed as a catch-all diet solution due to the variance in responses between subjects.


Following that hefty bit, it may be easy to say “Well, a GI-based diet is useless!” That’s not really the case, however. As previously stated, a good portion of low-GI/low-GL carbohydrate foods are really good for you, including fruits and vegetables. The understanding of glycemic index, however flawed the system may be, is partly responsible for the understanding of how “bad” carbs affect us and, by extension, how the “low fat/high carb” diet fads of the 80s and 90s were shown to be deleterious. The basic thing to understand about GI/GL is this: If it is a natural carbohydrate food with a low GI/GL, it’s almost guaranteed to be something great for your body; most of these foods contain fiber and nutrients and will intrinsically assist you in losing excess pounds in moderation (glycemic load, anyone?). If it’s a processed food with a low GI/GL, take precautions and do research before swearing by it. The system isn’t perfect, but it is a small step in the right direction in understanding optimal health.