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The glycemic index

The Glycemic Index (GI) is a fantastic tool for telling us what foods are good for us to eat. Even better: if you want to maximise the amount of fat burning your body does each day then you need to use the GI!


glycemic indexThe Glycemic Index (GI) is an index that tells us how quickly blood sugar (also known as blood glucose) levels will rise after eating a specific carbohydrate based food. Foods that create a slow rise in blood sugars rate lower on the glycemic index, and foods that create a faster rise in blood sugars rate higher. A slower rise in blood sugars is optimal for health, weight loss, energy levels, sporting performance, amongst other things! An easy way to remember that low GI is a slow release is that "low" is "slow"!

The glycemic index was originally created for diabetics to help them control their blood sugar levels, but for non-diabetics it has been developed into an extremely useful tool to help people make better food selections. Recently you may have noticed the "GI Symbol" has been appearing on Australian foods, and is more common to be used in marketing and advertisements for various products. Companies must apply for a license to use this symbol and pass several criteria and tests to be eligible. For more information see the GI Symbol website.

So what's all the fuss about, or how does it help me?! Let's take a closer look at what happens in your body when you eat: after you eat carbohydrates, your blood sugar (or blood glucose) levels start to rise as your digestive system breaks down the carbohydrates into a simple chemical compounds called glucose (or glycogen) and releases them into your blood stream. Your body likes to keep blood sugar levels within a narrow range, so as it begins to climb (see graph below) your body releases insulin (a storage hormone) from the pancreas to bring blood sugar levels back down. Insulin either forces your muscles to store the blood glucose for later use, or converts the blood glucose into fat, which is also stored. The key point to learn here is that the higher and faster the rise in blood sugars after eating, the greater the release of insulin. So high GI foods give you a higher insulin spike!

So why is high levels of insulin bad for me? Insulin is an important hormone that helps shuttle glucose and amino acids from the blood stream into your body's cells. Without insulin we wouldn't be able to store energy and this is not a good state of affairs! But while this storage process is a necessary function, it also has a bad side because while we are busy storing energy, the breakdown of body fat for energy use is severely inhibited. It's an either/or situation: you are either storing energy and not burning fat, or you are not storing energy and burning fat! So high insulin levels (coming from high GI foods) means low fat burning activity, and this is definitely a bad thing if you desire to lose weight!

Also, excess insulin has also been linked to chronic diseases and aging. So here's another reason not to eat high GI foods as a staple diet.

glycemic index Graph: The two lines show the difference between a high and a low GI food. The high GI food causes blood glucose and insulin levels to rise significantly, but they then fall below the starting level (which causes hunger cravings). The low GI response is a slight rise in glucose levels then a return to normal levels which is ideal for weight loss, good health, and a steady supply of energy.

If you still aren't convinced that low GI is the key to better health and more fat burning then consider this: when your blood glucose levels fall below normal levels it triggers a hunger craving. You can see on the graph that high GI foods not only drop fast but also tend to drop below your original or normal level. So high GI foods take your blood sugars way up high (that's the "sugar buzz" you often get) but then when it slams you back down it will trigger hunger pangs... which you guessed it, means you tend to reach for more high GI foods and so the cycle continues! It's a vicious circle and all that time you are burning low levels of body fat, as well as storing the energy coming in!


What does all this mean for better health and weight loss?

1. Stick to eating foods that are lower on the glycemic index, or when you do eat high glycemic foods, make sure that you combine them with sources of protein, fat, and fibre because these will slow the rise in blood sugar. Low GI foods are often: unprocessed, unrefined, whole, and fresh, so it is no wonder that low GI foods tend to be much healthier for us!

2. Low GI foods have the advantage of leaving you feeling fuller for much longer. For example, compare how full you fell after eating porridge than eating cocopops! Feeling full will make over-eating less likely and contribute to a sense of energy throughout the day. Breakfast is the perfect time to eat low GI because it sets you up for the rest of the morning and the whole day ahead.

3. Low GI foods give you a slow steady release of energy without sudden drops in blood sugar levels. It's these sudden drops that induce hunger cravings - often for more high GI foods! So always have low GI foods ready for snacks or make sure you eat low GI at every meal.

4. Sharp rises in blood sugar levels and the release of insulin places a hormonal stress on the body. Just like having a coffee gives you a "caffeine hit" which perks your whole system up, having high GI foods gives you a "sugar rush". This rush of energy is a stress on the system and can cause skin irritations, mood swings, and headaches. Eating low GI foods will reduce the amount of stress we are placing on our bodies, which will promote better health.

5. To further lower the insulin response to foods, you can engage in regular, intense exercise to help increase your insulin sensitivity. Weights training is a perfect activity, because increasing your lean mass means having more cells to "soak up" the release of blood sugars after eating. Intense exercise also ensures that blood glucose finds its way into muscle cells and not into fat cells, since glycogen levels are lower in your muscles and need replacing after intense exercise.

6. Eat 5-6 small meals a day rather than 2-3 large ones; this will help avoid the swings in blood sugars and insulin levels associated with eating less frequently. For instance, if you wait too long between meals you'll becoming hungry (ie have low blood sugar levels) and might be tempted into eating something high GI.... which puts us on that slippery slope! Better to have a steady low GI flow of energy throughout the day.


Common questions about the glycemic index:

Is GI the only criteria I should use to judge foods? No, you need to look at a number of factors when making food choices. For instance, whilst peanuts are very low GI at 14, they are very high in fat, and may not be the best choice for someone wishing to reduce energy intake and get weight loss. The GI is not the be-all and end-all of food selection, but another tool to help decide what is good for you to eat.

What effect does combing foods of different GI's have? The combination of a high GI food with a low GI food will result in a moderate GI meal. This is a good way to have high GI foods without suffering a sharp rise in blood sugars. You can also add protein, fibre, citrus or acidic condiments (eg lemon juice or vinegar), or fat to your meal to lower it's GI even further.

Should I cut out high GI foods altogether? Not necessarily. A balanced diet can certainly include some high GI foods, sugars and sweeter items. In fact, studies have shown very low sugar diets can lead to higher consumption of fat, perhaps to compensate for the loss of flavour in the diet. Studies also show that you don't need to change every food you eat to get a good reduction in your average blood glucose levels, just make sure you change the major items you eat to low GI, and this will help with weight loss. As always, it tends to be best to maintain a balanced diet.


If you are interested in seeing a complete glycemic index of foods check out the Glycemic Index website. They also list a number of books, most of them by the Australian professor who pioneered glycemic index research: Jenny Brand-Miller. She has a number of excellent books such as 'The GI Factor'. It is an easy to read guide with lists of foods and a lot of great meal ideas.


To find out more about the glycemic index, the GI, low GI foods, or your individual nutritional needs contact us!



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