The Glycemic Index Diet for Dummies (6 page)

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 indis 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.

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.

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:

Carbohydrates:
The body's primary fuel source, providing energy for the brain, muscles, and organs.

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

Fat:
Provides energy, but only when you've used up carbohydrates (that's why reducing body fat stores and losing weight is so tough).

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.

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 Appendix A to quickly look up the glycemic load of your favorite foods and find lower-glycemic foods to replace higher-glycemic ones when necessary.