Meri Raffetto, RD, is the founder and developer of Real Living Nutrition Services, providing online weight loss programs to empower people to make small changes to achieve lasting results. Meri specializes in weight management and heart disease prevention and is a member of the American Dietetic Association.

Glycemic Index Diet For Dummies 2nd Edition

By Meri Reffetto

John Wiley & Sons

Copyright © 2014 John Wiley & Sons, Ltd.
All rights reserved.
ISBN: 978-1-118-79056-4
CHAPTER 1

Introducing the Glycemic Index and How to Use It to Lose Weight

In This Chapter

* Surveying the ins and outs of the glycemic index

* Looking at how using the glycemic index can help you lose weight

* Recognizing that the glycemic index “diet” isn’t like diets you’ve tried before

* Reviewing the additional benefits of following a low-glycemic diet

The glycemic index was first introduced in the early 1980s as a way for people with diabetes to achieve tighter blood sugar control and improve their overall health. Only 62 foods were part of the original glycemic index research. Fast forward to today, and you find that hundreds of foods have now been tested. Companies are even working to develop lower-glycemic foods to meet growing consumer demand.

In this chapter, I review the research behind the glycemic index and explain how adding more low-glycemic foods to your diet can help you lose weight, embrace a healthier lifestyle, decrease your risk of heart disease, manage your blood sugar, increase your energy levels, and improve your mood. Sure, all of that may sound too good to be true, but the scientific research is clear: Looking beyond total carbohydrate content of foods into how different foods affect blood sugar and insulin levels opens up a doorway into good health.

Getting to Know the Glycemic Index

The glycemic index is a scientific way of looking at how the carbohydrates in foods affect blood glucose, or blood sugar, levels. Scientists know that all carbohydrates raise blood sugar, but the glycemic index takes this understanding one step further by figuring out how much a specific food raises blood sugar.

When you use the glycemic index to plan your meals and snacks, you’re following a glycemic index diet. It’s not a “diet” in the sense that there are specific meal plans you need to follow, lists of foods to eat and foods to avoid, and other types of rules that are all too familiar to people who’ve tried various weight-loss diet plans. Instead, the glycemic index gives you a method for selecting foods that meet your specific needs and desires.

TIP

You know those overlay maps, where you start with a very basic map, add an overlay with more detail, then add another overlay with yet more detail, and so on until you have a complete picture of a specific area? Think of using the glycemic index in a similar way.

[check] The first “overlay” is basic meal planning. Your body tells you it’s hungry and wants food.

[check] Next comes the layer of basic nutrition, which is all about balance. Your meal needs to include protein (chicken, fish, lean red meat, soy products, eggs, nuts/seeds), vegetables, healthy fats (olive oil, avocadoes, nuts) and starch (whole grains, potatoes, pasta) to keep your body happy. If you throw in a glass of milk and some fruit on the side, your body will be even happier.

[check] Finally, you add in the glycemic index for a complete picture. Because the glycemic index applies solely to foods that contain carbohydrates, it applies only to the vegetable, starch, milk, and fruit portions of your meal. Theoretically you already have an understanding of these foods’ nutritional values. The glycemic index completes the picture by telling you how these foods will impact your blood sugar, which affects everything from your energy level to your food cravings.

Now that you have a basic understanding of the glycemic index, check out the following sections for the scoop on how it’s measured and how an added bit of information makes it even more valuable.

Measuring the glycemic index

REMEMBER

The glycemic index ranks foods on a scale of 0 to 100 based on how quickly they raise blood sugar levels. Foods that raise blood sugar quickly have a higher number, whereas foods that take longer to affect blood sugar levels have a lower number.

To measure the glycemic index of a food, a specific weight of the digestible carbohydrates in the food (usually 50 grams, which is about 4 tablespoons of sugar) is fed to at least ten different people who volunteer for the study. Their blood sugar levels are measured every 15 to 30 minutes over a two-hour period to develop a blood sugar response curve. The blood sugar response of each food is compared to that of a test food, typically table sugar (glucose), which is assigned the number 100. The responses for each test subject are averaged, resulting in the glycemic index number for that food. Every individual person may have a slightly different glycemic (blood sugar) response to foods, which is why the tests use a number of volunteers and average their results together.

REMEMBER

The information on glycemic index (GI) lists is divided into three basic categories so you don’t have to get caught up in numbers and can instead focus on the primary goal of the glycemic index — choosing foods that keep your blood sugar levels more even, resulting in longer-lasting satiety (the feeling of fullness) and improved health. Here are the three categories:

[check] GI of 55 or less = low

[check] GI of 56 to 69 = medium

[check] GI of 70 or more = high

Introducing the glycemic load

Putting a numerical value on how various carbohydrate-containing foods affect blood sugar levels — the glycemic index — is great. However, the glycemic index is calculated using a standard weight of food, usually 50 grams. A food’s glycemic index actually changes based on the amount of it that you eat, which is why a standard weight amount is always used when calculating the glycemic index. In real life, you don’t always eat a standard amount of food. Sometimes you may eat two bowls of cereal at breakfast; other times you may eat one. Occasionally you want second helpings of pasta or an extra roll at dinner. You know what it’s like.

The glycemic index is calculated not only for a specific weight of food but also for eating just that one food. That’s great for researching how one particular food affects blood sugar levels, but what happens when you eat more than one food at a time, such as a peanut butter sandwich with a glass of milk and an apple?

This is where a little something called the glycemic load becomes important. I cover glycemic load extensively in Chapter 4, but here are the basics: The glycemic load applies the glycemic index to the amount of food you’re actually going to eat, or to the total amount of carbohydrate-containing foods in a meal or snack. To calculate the glycemic load (GL), multiply the glycemic index (GI) of a food by the amount of carbohydrates in the food and then divide by 100. For example, 1 cup of watermelon has a GI of 72 and contains 10 grams of carbohydrates. 72 × 10 = 720, and 720 ÷ 100 = 7, the glycemic load of 1 cup of watermelon. If you eat two cups of watermelon, use this calculation: 72 × 20 = 1,440; 1,440 ÷ 100 = a GL of 14.

What if you eat a turkey sandwich with two pieces of bread and drink one cup of fat-free milk? A slice of white bread has a GI of 70, and each slice contains 15 grams of carbohydrates. One cup of fat-free milk has a GI of 32 and contains 13 grams of carbohydrates. The GL for the meal is 25 (70 × 15 = 1,050, and 1,050 ÷ 100 = 10.5; 32 × 13 = 416; 416 ÷ 100 = 4.16). Add up each glycemic load 10.5 + 10.5 + 4.16 = 25.

REMEMBER

Just like the glycemic index, glycemic load levels are divided into three categories:

[check] GL of 10 or less = low

[check] GL of 11 to 19 = medium

[check] GL of 20 or more = high

TIP

A basic guideline is to keep your total daily glycemic load under 100. In this case, if you’re eating three meals per day and each meal has about the same glycemic load, you’ll be in a good range. To prevent yourself from going over, choose to balance a higher-glycemic meal with a lower-glycemic one or swap out a higher-glycemic food for a lower-glycemic one to reduce a meal’s overall glycemic load.

How Does the Glycemic Index Work for Weight Loss?

What does every traditional weight-loss diet have in common? Each one promotes its own twist on losing weight, but at the end they all come down to one truth — eat fewer calories. I’m not going to argue with that. Paying attention to the amount of calories you consume and increasing the number of calories you burn each day through exercise and just moving around is crucial for achieving and maintaining a healthy weight.

If counting calories was all you needed to do to lose weight, I could theoretically eat candy bars all day and lose weight as long as I kept under my daily calorie limit. However, there’s more to weight loss than just counting calories. Choosing healthier foods that provide energy and promote a strong, fit body is just as important as sticking to a calorie goal.

The glycemic index is a tool you can use as part of your overall weight-control and healthy-eating strategies. Why? Because the glycemic index goes beyond calories; it encourages you to look at the way foods are digested and metabolized in your body and what impact that has on your body weight and how full you feel after eating. If biology and chemistry weren’t your strong points in school, don’t worry. The glycemic index puts all the science together into a list of foods categorized by their effect on blood sugar and insulin.

Use a glycemic index list as a weight-loss tool by selecting low-glycemic foods or balancing out a high-glycemic food choice with a lower-glycemic one. There’s no one right way to do this. Nor is there a black-and-white approach where you’re either “on” or “off” the diet. Just use the information in the glycemic index list to add additional healthy benefits to your food choices.

The sections that follow delve into the three factors — blood sugar, carbohydrates, and insulin — that combine to make the glycemic index effective for weight loss. (Note: If weight loss is your primary goal, flip to Chapter 3 for more information on incorporating the glycemic index as a weight-loss strategy.)

Getting the 411 on blood sugar

Why all the fuss about blood sugar? Well, blood sugar is the primary energy source for every cell in the human body, especially brain cells. Blood sugar is the energy that powers your body, just like gasoline is the energy that powers your car. Although many people may falsely believe that any blood sugar is a bad thing, your body actually works hard to maintain even blood sugar levels to promote optimal health. The human body produces insulin to lower blood sugar levels and another hormone, called glucagon, to help raise blood sugar levels. Normally, blood sugar stays in the range of 70 to 140 milligrams of blood sugar per deciliter of blood (abbreviated 70–140mg/dL), no matter how much sugar or carbohydrates you eat — or don’t eat.

Hypoglycemia, or low blood sugar, occurs when blood sugar levels drop below 70mg/dL. Symptoms of hypoglycemia include blurry vision, a shaky feeling, and confusion. At the other end of the spectrum, hyperglycemia, or high levels of blood sugar, happens when the body doesn’t produce enough insulin or when insulin isn’t working the way it’s supposed to. The symptoms of hyperglycemia — increased thirst and increased urination are two of the more common ones — are sometimes tough to spot. Many people have elevated blood sugar levels for months or even years before they’re actually diagnosed with diabetes. Such chronically high levels of blood sugar not only damage blood vessels but also play a role in the progression of heart disease.

TECHNICAL STUFF

People with diabetes occasionally experience hypo- or hyperglycemia. Even people without diabetes may have fluctuations in blood sugar levels that leave them feeling tired or out of sorts. Using the glycemic index to choose your foods will help you keep your blood sugar levels within a healthy range. Chapter 2 covers the role of the glycemic index in managing healthy blood sugar levels in more detail.

REMEMBER

Using the glycemic index to lose weight can be especially helpful for people with insulin resistance (a common precursor of Type 2 diabetes). With insulin resistance, your body produces plenty of insulin, but your muscles resist the action of insulin, preventing it from doing its job (meaning your body holds onto blood sugar instead of getting rid of it). Your body keeps making more insulin in an attempt to lower blood sugar levels, and you’re stuck in a vicious cycle of insulin resistance that can lead to weight gain. Follow a low-glycemic diet, and you get a cascade of beneficial effects: Your blood sugar level doesn’t rise as high, which means your body doesn’t need to produce as much insulin, which in turn helps your muscles use blood sugar and insulin more effectively. (Check out Chapter 5 for more about insulin resistance and the glycemic index.)

Understanding the role of carbohydrates

Food is made up of three macronutrients that contain calories:

[check] Carbohydrates: The body’s primary fuel source, providing energy for the brain, muscles, and organs.

[check] Protein: The building block of body tissues. Rarely used for energy because it has other, more valuable uses.

[check] Fat: Provides energy along with carbohydrates at different rates depending on activity and endurance.

Health experts recommend that 40 to 60 percent of a person’s total calorie intake should come from carbohydrates. Admittedly, that’s a wide range, but that range exists for several reasons. Active people need more carbohydrates to fuel their muscles, and children and adolescents need carbohydrates to fuel growth. On the other hand, people who are sedentary need smaller amounts of carbohydrates.

Because carbohydrates are the body’s primary source of energy, it makes sense that just about every food group contains some carbohydrates. Fruits, vegetables, and grains are the primary sources of carbohydrates in foods, although milk, yogurt, and legumes also contain carbohydrates. The only food groups that contain no carbohydrates are animal meat and fat such as butter, margarine, and olive oil.

REMEMBER

Whenever I talk about the glycemic index, I’m really talking about foods that contain carbohydrates. Plenty of misconceptions about carbohydrates are floating around, with some people thinking that all carbs are bad and that you should throw out the whole lot if you’re trying to lose weight. Not true! Carbohydrates are an essential nutrient, and by using the glycemic index, you can choose foods that contain carbohydrates yet help you meet your weight goals.

The glycemic index helps you move beyond simply paying attention to the amount of carbohydrates you consume and gives you more specific information about how different types of carbohydrate-containing foods metabolize in your body and raise blood sugar levels. Because of the glycemic index, scientists know that foods that contain the same amount of total carbohydrate but have different glycemic index numbers will raise blood sugar levels differently.

Here’s an example: 1 cup of dark cherries and one medium ear of sweet corn both contain 15 grams of carbohydrates. If you only count carbohydrates, you’d expect both the cherries and the corn to raise your blood sugar levels equally, right? Go one step further and look at the glycemic index of the foods individually. The glycemic index of 1 cup of dark cherries is 63, whereas the sweet corn has a glycemic index of 48. Now you know that the sweet corn will cause a lower rise in blood sugar and insulin levels compared to the same amount of carbohydrates in the cherries. The calories are almost the same — 73 in the cherries and 84 in the sweet corn. The important difference when it comes to weight control is the foods’ glycemic index numbers: The lower the glycemic number, the lower the blood sugar response and required amount of insulin (a storage hormone that makes weight loss difficult). Use the Appendix to quickly look up the glycemic load of your favorite foods and find lower-glycemic foods to replace higher-glycemic ones when necessary.

(Continues…)Excerpted from Glycemic Index Diet For Dummies 2nd Edition by Meri Reffetto. Copyright © 2014 John Wiley & Sons, Ltd.. Excerpted by permission of John Wiley & Sons.
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