Diet Principle #4: Choose Foods With Low Glycemic Index and Glycemic Load
Say you were to eat a meal, then measured your blood sugar every 15 minutes while food was being digested. You'd find that some foods cause a rapid and higher rise in blood sugar than others. You could then compare blood sugar after various foods to that obtained after eating white sugar or white bread as a reference (they yield the most dramatic spike in blood sugar). This kind of comparison is called "glycemic index."
Put simply, foods with low glycemic index cause a slow, gradual rise in blood sugar. These tend to be protein and fat-containing foods like meats, dairy products, and vegetables and nuts. Foods with a high glycemic index cause a rapid, sharp rise in blood sugar—carbohydrates like candies, cookies, soft drinks, white bread, white flour pasta, and potatoes. Instant rice, white bread and other white flour baked products, and sugary cereals all raise your blood sugar just as if you were eating sugar straight from the sugarbowl. The glycemic index of the average American diet has climbed higher and higher over the past four decades as our intake of carbohydrates increases and we reach for more highly-processed foods.
High glycemic index foods provoke a sharp rise in insulin. The peak of blood sugar is then followed by a sharp drop to low blood sugar levels, or "hypoglycemia". Hypoglycemia triggers "hyperphagia", or an overwhelming urge to eat to compensate for low blood sugar. People experiencing this effect crave more carbohydrates. The result is a vicious cycle of high blood sugar followed by hypoglycemia and overeating. This is the powerful phenomena behind obesity in the U.S.
High insulin levels yields high triglycerides and low HDL. The greater availability of triglycerides creates triglyceride-rich particles, such as small LDL and VLDL. Repeated high levels of insulin eventually lead to a condition called "insulin resistance", or "pre-diabetes". This means that your body fails to respond to its own insulin, and sugar is unable to be cleared from the blood. Blood sugar then increases—this is diabetes. Even if you don't have diabetes but have "insulin resistance" with high insulin levels but normal blood sugars, the risk of heart attack is increased 3–5 fold.
Glycemic Index vs Glycemic Load
Generally it is assumed that simple carbohydrates increase blood glucose levels rapidly, and complex carbohydrates have a slower effect. However, recent work into the Glycemic Index (GI) and Glycemic Load (GL) has changed the understanding of the relationship between ingested carbohydrates and blood glucose levels.
The glycemic index (GI) is a measure of how fast a carbohydrate raises the blood sugar. Some carbohydrates are slow releasing, while the others are fast releasing. The higher the number, the greater the blood sugar response. All carbohydrates can be assigned a value, known as glycemic index, compared to glucose. The glucose is the fastest releasing carbohydrate so it has been assigned a glycemic index value of 100.
What is Glycemic Load?
A glycemic index value tells you only how rapidly a particular carbohydrate turns into sugar. It doesn't tell how much of that carbohydrate is in a serving of a particular food. Both the things are important to understand a food's effect on blood sugar. The glycemic index value alone does not give accurate picture of the food. The glycemic load (GL) takes both the things into account.
The glycemic load is the glycemic index divided by 100 multiplied by its available carbohydrate content (i.e. carbohydrates minus fiber) in grams. The following table lists GI and GL values of certain foods.
Ranking Glycemic Index(GI) Glycemic Load(GL)
High 70 and above 20 and above
Medium 56 to 69 11 to 19
Low 55 or less 10 or less
Take watermelon as an example of calculating glycemic load.
Glycemic Index = 72
In a serving of 120 grams, it has 6 grams of available carbohydrate.
The Glycemic Load = (72/100) x 6 = 4.32
By simply looking at the glycemic index value you will think that watermelon is not good for you, but its glycemic load is low, so it is safe to eat.
Foods that have a low glycemic index invariably have a low GL, while foods with an intermediate or high glycemic index range from very low to very high GL. Therefore, you can reduce the GL of your diet by limiting foods that have both a high glycemic index and a high carbohydrate content.
To optimize insulin levels, you should eat fruits, vegetables, and whole grains with low glycemic index and low GL values. The fiber contained in these foods slows down the release of sugars.
The values of glycemic index and glycemic load for a number of food items for a serving size are given below.
FRUITS Glycemic Index Serving Size (g) Glycemic Load
Apples 38 120 6
Apple juice,
unsweetened 40 250 11
Apricots 57 120 5
Apricots, in syrup 64 120 12
Apricots 31 60 9
Banana, ripe 51 120 13
Banana, under-ripe 30 120 6
Banana, over-ripe 48 120 12
Cherries 22 120 3
Cranberry juice 68 250 24
Custard apple 54 120 10
Dates, dried 103 60 42
Figs, dried 61 60 16
Grapefruit 25 120 3
Grapefruit juice,
unsweetened 48 250 9
Grapes 46 120 8
Grapes, black 59 120 11
Kiwi fruit 53 120 6
Lychee,
canned in syrup 79 120 16
Mango 51 120 8
You should always favor low vs. high glycemic load foods. For instance, avoid highly processed breakfast cereals made of puffed wheat or corn flakes (high glycemic load) and consider replacing with low-fat yogurt with blueberries and raw nuts (all low glycemic load), or an oat-based granola sweetened with sliced fruit. Some foods are so offensive in this regard that you should rarely indulge in them: soft drinks, white flour baked products like cakes and cookies, candies. Fruit juices, though they contain many desirable ingredients, still evoke the exaggerated blood sugar response and should therefore also be minimized. Try choosing foods in the low or intermediate glycemic load categories. When you do eat foods with a high glycemic index, consider eating raw nuts or adding oat bran, flaxseed, or other fibers to blunt the rise in sugar. Lowering the overall glycemic load of your diet can be an important contributor to weight loss. A switch from high to low glycemic load foods can be an effective way to gradually melt away excess pounds.
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