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How Does The Glycemic Index Impact Your Weight?

Glycemic Index Information

The term glycemia refers to one's blood sugar levels. Hyperglycemia indicates increased blood sugar levels. Hypoglycemia indicates decreased sugar levels.

The term glycemic index (GI) designates the degree to which a certain type of food increases blood sugar levels.

Glycemic Index Information

The glycemic index of a food is calculated by measuring the increase in blood glucose levels after ingesting 50 grams of the respective food. The glucose curve is plotted over a period of 2 hours after ingestion of the respective food, and the area under the curve is used to determine the glycemic index.

By definition, pure glucose is assigned a glycemic index of 100. The glycemic indexes of other foods range between 0 and 99. Obviously, this means that ingestion of pure glucose causes the greatest increase in one's blood glucose levels.

Glycemic Index Information
The Link between Glycemic Index and Weight Control:

  • Foods with a low glycemic index are beneficial for weight control (if consumed in adequate portions)
  • Foods with a high glycemic index are detrimental for weight control (even when consumed in the serving sizes recommended by the manufacturer)

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Here's why:
Food items with high glycemic index will cause one's blood glucose levels to rise sharply, thereby triggering the secretion of the hormone insulin in high amounts. Insulin has the role of removing glucose from the bloodstream - so it's only natural it will be heavily secreted in response to a high load of carbs entering the bloodstream all at once. Apart from removing glucose from the bloodstream, insulin also mediates the synthesis of triglycerides (fats), and their deposition in fatty tissues. Therefore, higher levels of insulin will result in the formation of more fats. To make things worse, the high amount of glucose delivered by the food ingested provides a plentiful substrate for the synthesis of fats. In other words, fats are formed from excess glucose delivered into the body.

To take it one step further: After the sharp rise in blood glucose levels and the corresponding heavy insulin secretion, the insulin produced quickly disposes of the glucose - removing it from the bloodstream as described above. The result is a sharp drop in blood glucose level, which is interpreted by our brain as... guess what? You guessed it - HUNGER. Therefore, foods with high glycemic index are likely to evoke rebound hunger a short time after the meal. Also, fatigue and exhaustion may occur due to the drop in blood glucose levels. In contrast, foods with low glycemic index are likely to sustain energy levels longer and curb hunger more effectively.

Glycemic Index Information
What's High? What's Low?

  • A glycemic index below 55 is considered low.
  • A glycemic index between 55 and 69 is intermediate.
  • A glycemic index of 70 or above is considered high.

Glycemic Index Information
The GI of Common Food Items:

  • Glucose - 100 (highest GI among all food items)
  • Refined Sugar (Sucrose) - 69
  • Lactose (the carb present in dairy products) - 46 (roughly half the glycemic index of glucose)
  • Fructose (the carb present in fruit) - 20 (1/5 the glycemic index of glucose
  • White Bread - 71
  • Whole Grain Bread (Wheat) - 50
  • Pasta (enriched flour) - 40-55 (depending on the brand)
  • Pasta (whole grain) - 37-40
  • Rice (white, cooked) - 70
  • Rice (whole grain) - 55
  • Rice Gruel - 90
  • Potatoes (baked) - 85
  • Potatoes (mashed) - 95
  • Milk (unsweetened) - 32
  • Yogurt (natural unsweetened) - 15
  • Yogurt (with fruit and sugar) - roughly 35
  • Bananas - 60
  • Strawberries - 40
  • Apples - 38
  • Pears - 42
  • Peaches - 35
  • Pineapples - 62
  • Oranges - 44
  • Mango - 55
  • Watermelon - 72
  • Walnuts- 15
  • Honey - 58

Glycemic Index Information
The Glycemic Load:

The glycemic load (GL) is a relatively new way of assessing the impact of a given food on the blood glucose level. It takes into account not only the type of carbohydrates in the respective food, but also the amount of these carbohydrates in one serving of the respective food. As such, the glycemic load gives a more accurate picture of the effects of the respective food on blood glucose levels than the glycemic index alone. For example: Even though watermelon has a relatively high glycemic index (72), the amount of sugars per serving of watermelon is quite low, so watermelon has a low glycemic load.

Current Consensus:
  • A GL of 20 or more is considered high.
  • A GL between 11 and 19 is medium.
  • A GL of 10 or less is considered low.

Glycemic Index Information
Interesting GI Facts:

Overall, foods containing complex carbs (with long carbohydrate chains) tend to have a lower glycemic index, since they take longer to be broken down in the intestine prior to being absorbed in the bloodstream. This is especially true for whole grain products (such as whole grain bread, cereals, rice, or pasta), which in addition to starches also contain high amounts of fiber that delays the absorption process.

The glycemic index applies primarily to foods rich in carbohydrates - since these are the ones to cause the most increase in the blood glucose level. However, we must keep in mind that foods rich in proteins and/or fats can be used by our body to generate glucose (mainly by conversion in the liver), and therefore may also cause an eventual rise in blood glucose levels. However, this increase will be much less and much more gradual as compared to foods rich in carbohydrates. The conclusion is that foods rich in protein and/or fat (and low in carbohydrates) have a low glycemic index. To take it one step further:

  • Foods rich in protein are largely beneficial for a weight loss program.
  • Foods rich in unsaturated fats (as opposed to saturated fats) are largely beneficial for a weight loss program, if consumed in adequate portions.

The South Beach Diet uses the glycemic index to determine what foods are suitable for a weight loss program. The mainstay of this diet is avoidance of foods with high glycemic index (i.e., foods containing high amounts of "bad carbs", most notably refined sugars and starchy products containing enriched flour).

All in all, this is a very sound criterion for a successful weight loss program. A low glycemic index diet is one of the most effective ways to loose weight and keep it off. The tricky part, however, is how to pick the foods for your low glycemic index diet. Let's take a closer look at this aspect:

Glycemic Index Information
Picking Foods for a Glycemic Index Diet:

At first glance, it all seems straightforward: Use whole grain products (i.e., breads, rice, pasta, and cereals - all of these should be whole grain)... Eat plenty of fruit and vegetables... Eat lean meats and soy products... Avoid candy, cakes, pies, ice-cream, cookies, and other sugary products... Avoid regular soft drinks... Avoid alcoholic beverages... And that's about it! Right...?
... Right!

HOWEVER: You must also avoid some very commonplace traps. For instance:
Let's say you are considering buying a box of 'Honey Nut Cheerios'. It's a cereal, right? It says 'whole grain' on the box... So it should have a low glycemic index, right?
WRONG! The problem is, our cereal (like many other items on the market), contains more than one type of carbohydrate:  It so happens our 'Honey Nut Cheerios' are artificially sweetened, containing a fair amount of added sugar (which is refined sugar with high glycemic index).

So the question is:
In the real world (grocery store), how can you tell which products have a low glycemic index?

And here's the solution, which happens to be simple and smart:
You can tell by looking at the food label.
On our box of 'Honey Nut Cheerios', under Nutrition Facts, you will find the following (among others):
  • Total Carbohydrate 22 g (per serving)
  • Dietary Fiber 2g
  • Sugars 9g
  • Other carbohydrate 17 grams
This is the clue we are looking for:
  • The term sugars on the food label indicates "bad carbs" of high glycemic index, which should be avoided.
  • The term other carbohydrates on the label refers to complex carbohydrates of lower glycemic index (starches, etc).

When purchasing any product that bears a nutrition label, always look for this clue, and remember: You want the sugars to be as low as possible. (In the regular Cheerios, for instance, the amount of sugars is 1 gram. )
Acceptable amounts of sugars in a cereal should probably be no higher than 6-7 gram per serving.
Note: Cereals can be sweetened to taste using a zero-calorie sweetener such as Splenda (Sucralose).

Easy tips for choosing low glycemic index foods:

  • Avoid sweets such as cakes, pies, candy, ice cream, sweetened fruit juices or regular soft drinks.
  • Use diet drinks whenever possible. (Regular Pop is a totally unnecessary source of sugars).
  • Avoid alcohol. Many alcohol products are naturally high in sugars. Additionally, alcohol is very caloric in itself, and is burned preferentially by the body (leaving all other nutrients to be stored as fat deposits).
  • Avoid cocktail drinks containing alcohol with added sugar and/or cream (e.g., Margarita, Mudslide, Pina Colada, etc). These can be tremendously damaging to a weight loss program.
  • For baking and cooking, use artificial sweeteners such as Splenda (Sucralose) whenever possible. There are plenty of recipes designed especially for this purpose. They allow you to replace up to half the sugar in your dishes and desserts with Splenda, without sacrificing taste or texture. For specific details, check out these links:
    Cooking with Sugar Substitutes
    Splenda Recipe Index
  • Read the food labels in the grocery store: Whenever you find a high content of sugars (more than 6-7 grams per serving), it's a hint the respective product has a high glycemic index and is best avoided.*


*For fresh and canned fruit, the healthy sugar limit can be increased to 15-16 gram per serving, since fructose (the main sugar in fruit) has a low glycemic index. Higher sugar levels (up to 20 gram per serving) may be acceptable for canned fruit - provided adequate portion sizes are respected.

Return from "Glycemic Index Information" to "Carb Facts"








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