The lowdown on glycemic index

and glycemic load

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If you have diabetes, you probably know you need to monitor your carbohydrate intake. But different carbohydrate-containing foods affect blood sugar differently, and these effects can be quantified by measures known as the glycemic index and glycemic load. You might even have been advised to use these numbers to help plan your diet. But what do these numbers really mean — and just how useful are they?

What these numbers measure

The glycemic index (GI) assigns a numeric score to a food based on how drastically it makes your blood sugar rise. Foods are ranked on a scale of 0 to 100, with pure glucose (sugar) given a value of 100. The lower a food's glycemic index, the slower blood sugar rises after eating that food. In general, the more cooked or processed a food is, the higher its GI, and the more fiber or fat in a food, the lower its GI.

But the glycemic index tells just part of the story. What it doesn't tell you is how high your blood sugar could go when you actually eat the food. To understand a food's complete effect on blood sugar, you need to know both how quickly it makes glucose enter the bloodstream and how much glucose it can deliver. A separate measure called the glycemic load does both — which gives you a more accurate picture of a food's real-life impact on your blood sugar. Watermelon, for example, has a high glycemic index (80). But a serving of watermelon has so little carbohydrate that its glycemic load is only 5.

Get your copy of Healthy Eating for Type 2 Diabetes

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In this report, you’ll learn about the components of a healthy diet for people with diabetes, as well as how to work with a dietitian, how to develop a meal plan, and how to fit physical activity into your schedule. You will learn how to recognize portion distortion, make wise choices while dining out, and stay on track with your weight-loss plan. Best of all, we’ve included 40 original recipes so you can put this advice into practice — starting today.

Should you eat a low-GI diet?

Some nutrition experts believe that people with diabetes should pay attention to both the glycemic index and glycemic load to avoid sudden spikes in blood sugar. The American Diabetes Association, on the other hand, says that the total amount of carbohydrate in a food, rather than its glycemic index or load, is a stronger predictor of what will happen to blood sugar. And some dietitians also feel that focusing on the glycemic index and load adds an unneeded layer of complexity to choosing what to eat.

The bottom line? Following the principles of low-glycemic-index eating is likely to be beneficial for people with diabetes. But reaching and staying at a healthy weight is more important for your blood sugar and your overall health.

If you'd like to give low-glycemic-index eating a try, click here to see our table of the glycemic index and load for over 100 common foods.

And for more information on how to live well — and eat well — with type 2 diabetes, buyHealthy Eating for Type 2 Diabetes, a Special Health Report from Harvard Medical School.

Exercising safely with diabetes

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If you have diabetes, exercise is one of the best things you can do for your health. It can improve your sensitivity to insulin and help you build muscle and shed excess fat, all of which go a long way to keeping this condition under control. However, you'll likely need to take a few more precautions when exercising than someone who doesn't have diabetes.

First, consult your doctor before starting or changing a fitness routine. This is especially important if you are overweight or have a history of heart disease, peripheral vascular disease, or diabetic neuropathy. For people who are 35 or older and who have had diabetes for more than 10 years, current guidelines recommend having a complete physical exam before beginning a new exercise program. Although not performed routinely, you may also have an exercise tolerance test (also known as a treadmill test) to monitor the performance of your heart and your blood pressure during exercise. The results can help you and your doctor determine the intensity of exercise that's best for you

Get your copy of Diabetes

This Special Health Report will help you better understand and manage your diabetes. It includes detailed, updated information about medications and alternative treatments for diabetes, and a special section on weight-loss strategies. You’ll also learn the basics of how your body metabolizes sugar, how and when to monitor your blood sugar, and how to cope with both short- and long-term complications of the disease. Most importantly, you’ll see that it’s not just possible to live with diabetes — it’s possible to live well.

In general, the best time to exercise is one to three hours after eating, when your blood sugar level is likely to be higher. If you use insulin, it's important to test your blood sugar before exercising. If the level before exercise is below 100 mg/dL, eating a piece of fruit or having a small snack will boost it and help you avoid hypoglycemia. Testing again 30 minutes later will show whether your blood sugar level is stable.

Experts also caution against exercising if your blood sugar is too high (for example, over 250 mg/dL), because exercise can sometimes raise blood sugar even higher.

Because of the dangers associated with diabetes, always wear a medical alert bracelet indicating that you have diabetes and whether you take insulin. Also, keep hard candy or glucose tablets with you while exercising in case your blood sugar drops precipitously.

For more on how to live well after you've been diagnosed with diabetes, buy Diabetes: A plan for healthy living, a Special Health Report from Harvard Medical School.

Healthy Eating for Type 2 Diabetes

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•	SPECIAL BONUS SECTION: Healthy recipes
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