Taking Portion Size into Account with the Glycemic Load
In This Chapter
▶ Seeing how glycemic load improves the practicality of the glycemic index
▶ Determining a particular food’s glycemic load
▶ Using the glycemic load to increase the kinds of foods you can eat
▶ Looking at the glycemic load levels of common foods
The glycemic index is a wonderful tool for determining your best carbohydrate-containing food choices. But like many things in life, it has its limitations, specifically those relating to the amount of food you’d actually eat in a serving, mixed foods, and even different food-preparation methods. As the glycemic index diet has grown more and more popular, new concepts and information are doing their part to lessen the impact of some of these limitations.
One such concept is the glycemic load. Although the glycemic index shows you the quality of your carbohydrates (as explained in Chapter 2), the glycemic load breaks those carbs down into the quantity you’d typically eat at one sitting, which can turn a high-glycemic food into a low-glycemic food. Glycemic load is one of the most important concepts to understand so you can make the best food choices based on a realistic portion size. That’s why I share the basics of it with you in this chapter.
Going from the Glycemic Index to the Glycemic Load
The glycemic load, which is based on the idea that a high-glycemic food eaten in small quantities produces a blood sugar response that’s similar to the response produced by low-glycemic foods, is a much more useful tool for your day-to-day use. It allows you to have more food choices than the glycemic index does alone. That’s good news because no one wants to be too restricted in what he or she can eat. But to create the glycemic load, researchers first had to come up with the glycemic index.
The glycemic index concept was developed in 1981 by two University of Toronto researchers, Dr. Thomas Wolever and Dr. David Jenkins. Their research compared the effect of 25 grams of carbohydrates (just picture two slices of bread if you’re not familiar with the metric system) to that of 50 grams of carbohydrates (picture four slices of bread) to see whether the smaller amount created a lower glycemic response in the human body based on the lower quantity of carbohydrates.
However, with the amount of carbohydrates varying so much in different foods (for instance, some fruits and vegetables have only 5 grams of carbohydrates whereas starches have up to 15 grams), 50 grams of carbohydrates (the standard amount used for glycemic index testing) doesn’t always depict the portion size a person may typically eat. To account for this variation, in 1997, Harvard University’s Dr. Walter Willet created the glycemic load, which calculates the quality and quantity of carbohydrates at a meal. The fact that the glycemic load takes portion size into account is quite helpful because the average person is far less likely to eat 50 grams of a particular food in one sitting.
Looking at portion sizes and carbohydrate grams can give you a better understanding of the glycemic load. Although foods vary, Table 4-1 breaks down the average amount of carbohydrates in each carbohydrate-containing food group based on a particular portion size.
As you can see from Table 4-1, the amount of carbohydrates in a serving of a particular food depends as much on the portion size as it does on the food itself. So consuming 50 grams of carbohydrates (which is definitely more than one serving) will have a dramatic impact on your blood sugar. Take car- rots, for example. Carrots have a high glycemic index when cooked (41 to be exact), yet they’re considered a nonstarchy vegetable. To consume 50 grams of carbohydrates in carrots, you’d have to eat 5 cups! I don’t know about you, but even though I like carrots, 5 cups is a bit much (not to mention it may turn your skin orange). Because the amount of carbohydrates in carrots is so low compared to their average portion size, the glycemic load of carrots is low as well.
On the other hand, a serving of instant white rice, another high-glycemic food with a glycemic index of 72, has around 15 grams of carbohydrates per 1⁄3-cup serving. To eat 50 grams of carbohydrates in instant white rice, you’d have to eat slightly more than 1 cup of rice — a fairly typical portion size for most people. This portion size means the glycemic load for instant white rice doesn’t change much from the food’s glycemic index.
The glycemic index compares the potential of foods with equal amounts of carbohydrates to raise blood sugar. The purpose of the glycemic load is to have a usable indicator of the glycemic index that takes portion size into account. Although adding glycemic load to the mix may cause the glycemic index of some foods, such as white rice, to remain the same, it opens up the door for enjoying more foods that may have a high glycemic index but a low glycemic load based on different portion sizes.
Calculating Glycemic Load
Whereas calculating the glycemic index requires human clinical trials (as explained in Chapter 2), the glycemic load is a little simpler to determine. As long as you have some key pieces of information, you can calculate the glycemic load number and then see whether that number fits into the low, medium, or high category. The next few sections walk you through the basics.
Doing the math
The glycemic load uses a specific calculation. So as long as you know the glycemic index of a food and the grams of available carbohydrates (total carbohydrate minus fiber) in that food, you can figure out that food’s glycemic load. Here’s the calculation:
Glycemic index × Grams of carbohydrates ÷ 100
Try working out the calculation for a 1⁄2-cup serving of raw carrots, which have about 8.6 grams of available carbohydrates and a glycemic index of 45. (Note: I’ve rounded the numbers for simplicity’s sake. Feel free to do the same in your own calculations.)
45 × 8.6 = 387 ÷ 100 = 3.9 glycemic load
Want to calculate the glycemic load of instant white rice instead? Well, a portion size of around 2⁄3 cup of white rice has about 36 grams of available carbohydrates and a glycemic index of 72. Here’s the math:
72 × 36 = 2,592 ÷ 100 = 26 glycemic load
To find the amount of available carbohydrates in packaged foods, simply check the nutrition facts label. If the food is raw, like carrots or apples, you can use Table 4-1 as your reference for estimating the amount of available carbohydrates because it gives you the average grams of carbohydrates for the listed portions.
Figuring out what the numbers mean
Knowing how to calculate the glycemic load of a food is great, but it’s not quite enough. The end measurement is what’s most important to know. Similar to the glycemic index, the glycemic load is measured as low, medium, and high, rankings that help you determine your best choices for realistic portion sizes.
The measurements for glycemic load are as follows:
✓ Low: 10 or less
✓ Medium: 11 to 19
✓ High: 20 or more
After you know the glycemic load of a food, think of these rankings and plop your food into place. Thanks to the preceding section you know that carrots have a glycemic load of 3.9. That’s less than 10, so carrots have a low glycemic load. White rice, with its glycemic load of 26, has a high glycemic load because 26 is greater than 20.
When you don’t have time to calculate the glycemic load and match it up with the right measurement, keep in mind that foods with the least amount of carbohydrates (think vegetables and fruits) tend to have a lower glycemic load than starchy foods (such as rice and pastas).
Factoring in portion sizes
Perhaps one of the greatest beauties of the glycemic load is that researchers have embraced it as the main standard of measurement, which means it’s already calculated for you in most any glycemic index list. Three cheers for not having to drag a calculator with you everywhere you go! The variable in this info, however, is portion size. If you’re eating more or less than the portion size stated in the list you’re looking at, you need to account for possible fluctuations in the glycemic load.
To better see what I mean, consider the following different portion sizes of jasmine rice:
You can clearly see how the different portion sizes have a dramatic impact on the glycemic load. The higher the portion size, the greater the glycemic load will be. You can also see that, regardless of the calculation, the glycemic load for jasmine rice is so high that this food item isn’t going to dip into the medium or low category very easily.
To see what happens in the case of a food that borders on being low-glycemic, take a look at brown rice, which has a glycemic index of 50:
The smaller portion size still doesn’t bring the glycemic load of brown rice down to a low level, but it does keep it within the medium range. Increasing the portion size raises the glycemic load to the high level.
Last but not least, check out what happens to the glycemic load when you play with the portion size of a low-glycemic food such as kidney beans, which have a glycemic index of 34:
In this case, the two smaller portion sizes fall into a low glycemic load, and the larger one moves into the medium range.
I’ve shown you these three examples so you can see exactly how portion size affects glycemic load, but I promise I won’t make you do math every time you eat! Just knowing the portion size used in Appendix A’s list will help you determine how much to eat. If the portion used is 2⁄3 cup and that food ends up being low-glycemic, you know you can easily eat that amount or less.
Of course, determining glycemic load based on portion size isn’t an exact science, so sticking to low- to medium-glycemic foods within a reasonable amount is just fine. The beauty of this tactic for weight loss is that it keeps you eating portion sizes within a good calorie range. Limiting your rice servings to 1⁄3 to 2⁄3 of a cup is a great place to be. If you increase that portion size to 1 to 2 cups, then you begin to not only increase your glycemic load but also your calorie intake.
Embracing High-GI/Low-GL Foods
In the early days of the glycemic index’s popularity, experts appeared on television screens next to a table full of foods, talking about which ones were good and which ones were bad. Almost always they came to high-glycemic foods such as potatoes and watermelon and announced them as being equivalent to pure sugar. First of all . . . of course foods that contain mostly carbohydrates are all sugar . . . all carbohydrates break down into sugar, so that’s a bit of an unfair comment to begin with. But in the experts’ defense, they were operating with the glycemic index alone.
Thanks to the glycemic load, carrots and other high-glycemic fruits and veggies that got such a bad rap aren’t considered so bad for you anymore. That’s a darn good thing in my book because those same fruits and veggies are loaded with important nutrients.
What should my daily glycemic load be?
You don’t want to get so bogged down with numbers that you avoid carbohydrate- containing foods altogether; that’s neither a healthy choice nor one that promotes weight loss. To keep yourself on track for weight loss, your glycemic load for the day should be no less than 60 and no greater than 80. (Staying within the 80 to 120 range is ideal for weight maintenance.) Spread this out throughout the day to balance the glycemic load of all of your meals and snacks, aiming for a glycemic load of around 20 per meal.
To lower your daily glycemic load, try
✓ Increasing your intake of fruits, vegetables, nuts, and legumes
✓ Monitoring portion sizes of high-glycemic, starchy foods (such as white rice, pasta, and white breads) as well as sweets and sugars
If you’re one of those people following the old rules, or if you’ve been leery of following a low-glycemic diet because it puts certain foods such as watermelons in the “bad” category, I’m happy to tell you to take these foods off of your taboo list. The following foods not only have a low glycemic load but are also healthy, low-calorie choices:
✓ Cantaloupe (GI 65; GL 4): This fruit offers a full array of nutrients, including vitamin C, vitamin A, potassium, and fiber.
✓ Papaya (GI 59; GL 10): This incredible fruit that you may not have eaten much has a rich, tropical taste and is high in vitamin A, vitamin C, potassium, folate, magnesium, and fiber.
✓ Pineapple (GI 59; GL 7): Being a tropical fruit, pineapple is naturally loaded with vitamin C, but it also contains a special substance called bromelain, which has shown potential as an anti-inflammatory as well as a digestive aid.
✓ Pumpkin (GI 75; GL 3): I’m happy to report that you can safely include pumpkin in your glycemic index diet thanks to its low glycemic load of 3.
This food is an excellent source of vitamins A and C as well as fiber. It’s also wonderfully sweet and can be used in everything from soups to healthy desserts. (Head to Chapter 19 for a to-die-for Crustless Pumpkin Pie recipe.)
✓ Watermelon (GI 72; GL 4): This delicious summer fruit may at first look like a high-glycemic food with its glycemic index of 72, but it actually has a very low glycemic load. Why? Because it’s made up of a lot of water, hence the name. Watermelon is also loaded in antioxidants with high levels of both vitamin C and vitamin A. It also contains lycopene, which is shown to be helpful for heart health.
When you take glycemic load into account, you find that nearly all fruits and vegetables are acceptable on your low-glycemic diet. This is an important realization because fruits and veggies (which are naturally low in calories) also provide the majority of nutrients and fiber in your diet. Including five to nine servings of fruits and vegetables in your diet will help you lose weight in a way that you can eat plenty of food and not starve yourself!
Checking Out How Glycemic Load Varies among Popular Foods
The information in this section is designed to provide you with some insight into how the glycemic load varies among popular food choices. As you can see in Table 4-2, fruits and vegetables typically end up on the low end whereas the more starchy foods, such as potatoes, rice, and pasta, end up on the medium to high end.
Your goal is to pick low- to medium-glycemic foods most of the time.
Notice the different portion sizes and their glycemic load measurement. Some foods are clearly a slam dunk as far as being a healthy choice, but others are a little gray. For example, if you look at spaghetti, you see that it has a medium glycemic load for a portion size of ¾ of a cup. Spaghetti is therefore fine to eat in that amount, or you can even lower the glycemic load a little by eating just 1⁄2 of a cup. But if you go over the 3⁄4-cup portion size, you’re entering into high-glycemic territory.
If the idea of portion size’s effect on glycemic load still seems confusing, don’t get discouraged in your efforts to understand it. I promise that after a while you’ll get the hang of looking at the glycemic load of a food compared to just its portion size.
0 comments:
Post a Comment