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High-glycemic-index foods, such white bread, soda crackers, instant oats, are rapidly digested and cause marked fluctuations in blood-sugar levels.

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THE QUESTION

I've been told to reduce my carbohydrate intake in order to control my blood sugar and lose weight. I now eat less bread, crackers and potatoes. But my weight hasn't budged and my blood sugar is still in the pre-diabetes range. Are there other less obvious sources of carbohydrate I should watch out for?

THE ANSWER

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When people think of carbohydrates, the best-known sources such as bread, cereal, pasta and potatoes undoubtedly come to mind. But there are many other high-carbohydrate foods that may be slipping under the radar. Fruit, squash, beans and lentils, quinoa (no, it's not a protein food), avocados, milk, yogurt and tomato sauce, for example, are chock full of carbs.

What are carbohydrates?

The carbohydrate family includes simple sugars, starches and dietary fibre. Fructose (found in fruit, honey, agave nectar and corn syrup), sucrose (white sugar, brown sugar, maple syrup) and lactose (milk, yogurt, cheese) are simple sugars many of us consume every day.

Starches, also known as complex carbohydrates, are long chains of hundreds or thousands of glucose units – the simplest form of carbohydrate – linked together. Starches are stacked side by side in a grain of rice, slice of bread and flake of breakfast cereal.

Other starchy foods include oats, rye, barley, corn, legumes (e.g., lentils, black beans, kidney beans), winter squash (e.g., acorn, butternut, hubbard) and, of course, potatoes.

Dietary fibre is the third type of carbohydrate. Unlike with sugars and starches, though, the body can't break the bonds that hold fibre's carbohydrates together. As a result, fibre remains undigested and provides few, if any, calories.

Complex carbs not created equal

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Ultimately, carbohydrate-rich foods end up in your bloodstream as glucose, the body's primary source of energy. But all carbohydrates don't raise your blood glucose in the same way. Some are digested and absorbed into the bloodstream quickly, others more slowly.

The speed at which glucose enters your bloodstream can affect your hunger, your appetite, your energy level and your blood-sugar control. The glycemic index (GI) is used to indicate how much a food raises blood-glucose levels.

High-GI foods (e.g., white bread, white rice, soda crackers, refined breakfast cereals, instant oats, baked Russet potatoes, mashed potato, raisins, watermelon, table sugar, sugary drinks) are rapidly digested and cause marked fluctuations in blood-sugar levels.

Low-GI foods (e.g., 100% stoneground bread, steel-cut oats, 100 per cent bran cereal, brown rice, quinoa, white and whole wheat pasta, sweet potatoes, apples, bananas, berries, oranges, legumes, yogurt, milk) are slowly digested and absorbed and produce gradual rises in blood sugar.

Eating a diet based on low-GI foods can help to improve blood glucose as well as control appetite and delay hunger. You're off to a good start by eating less bread, crackers and potatoes since many of these foods score high on the glycemic index scale. But there is more to consider.

Too much of a good thing?

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Even healthy low-GI carbohydrates can contribute to elevated blood sugar and weight gain. As nutritious as they are, it's entirely possible to overeat quinoa (222 calories, 34 grams of carbohydrate per one cup) chickpeas (210 calories, 25 g of carbohydrate per cup) and sweet potato (249 calories, 50 g of carbohydrate per cup). That's especially true if you need to watch your calorie and carbohydrate intake.

To ensure that you're not overdoing it, measure your starchy foods. For weight loss, I generally recommend no more than two-thirds of a cup of cooked brown rice, quinoa or whole-grain couscous or one cup of pasta at a meal for women; for men, no more than one cup of cooked whole grain or 1.5 cups of pasta.

Consider your fruit intake, too. Unlike non-starchy vegetables (e.g., lettuce, broccoli, green beans, bell peppers), fruit isn't a "free" food that can be eaten in unlimited quantities.

For instance, one large apple delivers 116 calories and 30 g of carbohydrate. As a snack that's fine, but finishing a carbohydrate-containing meal with fruit for dessert can send too much glucose into your bloodstream.

Limit your fruit intake to two or three servings per day. If you enjoy having fruit with a meal, reduce your portion size of starch at that meal.

How much carbohydrate?

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Current dietary guidelines recommend that total carbohydrates make up 45 per cent to 65 per cent of your daily calories. If you eat, say, 1,800 calories per day, that means you can consume 202 g to 292 g of total carbohydrates.

The math: 1,800 x 0.45 = 810 calories; 810/4 = 202.5 g carbohydrate. (One gram of carbohydrate has four calories.) A 1,400-calorie diet translates into 157 g to 227 g of carbohydrate per day. Spread out your carbohydrate intake throughout the day.

People who need to lose excess weight and those who are physically inactive should aim for the lower end of the range.

The smallest contributor to your total carbohydrate intake – less than 10 per cent of daily calories – should be added sugars.

Final word

Being overweight is the single most important contributor to Type 2 diabetes, especially if you carry excess weight in your abdomen. If you are overweight, losing 7 per cent to 10 per cent of your current weight can cut the chances of developing Type 2 diabetes in half.

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Besides carbohydrates, assess other foods that might be contributing unnecessary calories to your diet. Is your portion size of healthy protein foods, such as salmon or chicken, too large? Are you heavy-handed with salad dressing or cooking oil? Do you snack on a few handfuls of almonds instead of one?

Physical activity is also an essential part of a diabetes-prevention plan. Regular exercise reduces blood glucose and body fat. Experts recommend moderate-intensity exercise for 30 minutes at least five days of the week.

How much carbohydrate am I eating?

The following chart lists grams of "available" carbohydrate for selected foods. Available carbohydrates are the amount of carbohydrates that affect blood glucose (e.g., grams of total carbohydrate minus grams of fibre).

Food/Beverage: Carbohydrate (grams)

Bagel, Tim Hortons 12-grain: 49 g

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Bread, whole wheat, 1 slice (35 g): 14 g

Brown rice, 1 cup cooked: 41 g

Corn, 1 cob: 12 g

Popcorn, air-popped, 3 cups: 15 g

Quinoa, 1 cup cooked: 34 g

Spaghetti, whole wheat, 1 cup cooked: 31 g

Bran flakes, 1 cup: 25 g

Granola, homemade, 1/2 cup: 27 g

Oatmeal, 1 cup: 24 g

Kellogg's Vector cereal, 1.25 cup: 41 g

Black beans, 1 cup: 26 g

Chickpeas, 1 cup: 25 g

Edamame, 1 cup: 4 g

Lentils, 1 cup: 25 g

Avocado, 1/2: 4 g

Banana, 1 medium: 24 g

Blueberries, 1 cup: 18 g

Dried cranberries, sweetened, 1/4 cup: 23 g

Orange, 1 large: 17 g

Orange juice, 1 cup: 28 g

Pear, 1 medium: 21 g

Milk, skim, 1 cup: 13 g

Yogurt, plain, 3/4 cup: 6 g

Yogurt, vanilla, 3/4 cup: 20 g

Almond milk, unsweetened, 1 cup: 0 g

Almond milk, original (unflavoured), 1 cup: 7 g

Almond milk, vanilla, 1 cup: 12 g

Barbecue sauce, 2 tablespoons: 14 g

Honey, 1 tablespoon: 17 g

Ketchup, 2 tablespoons: 10 g

Table sugar, 1 tablespoon: 12.5 g

Tim Hortons double-double coffee, large: 30 g

Leslie Beck, a registered dietitian, is based at the Medisys clinic in Toronto.

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