Low GI Diet by Sue Kira

by sue

Low GI Diet

by Sue Kira, Naturopath & Clinical Nutritionist

Introduction to a Low GI diet

GI Foods

Factors to consider with a low GI diet

Case study: low GI diet for dysglycaemia control

Introduction to a Low GI diet

Glycemic Index (GI) is a way of ranking carbohydrates (sugar and starches) according to their effect on blood sugar levels.

The lower a food’s GI value, then the slower the sugar release from the food. This means that blood sugar rises less severely when you eat low GI carbohydrate-based foods. Examples of low GI foods are whole foods including their fibres, such as fresh raw apples (but not apple juice), nuts, grains and seeds, meats, eggs, and fish.

Conversely, the more easily a sugar is released from food or drink, or the more sugar there is in those substances, then the higher the GI rating for that carbohydrate. High GI carbs release blood sugar more quickly into the blood, creating what we know as a sugar spike.

After an initial spike from sugar, the pancreas releases insulin to bring the blood sugar levels down. Examples of high GI foods are sugar, lollies, soft drinks/soda, and fruit juices.

Avoid sugary foods to help prevent blood sugar spikes and drops.

It is beneficial for most people to be on a low GI diet and especially important for those who have diabetes or various forms of dysglycaemia such as hypoglycaemia (poor blood sugar control).

Low GI foods tend to make it easier to lose weight, while foods high on the GI scale can help with energy recovery after exercise, or to offset a hypo (insufficient) glycemia attack. Long-distance runners tend to favour foods high on the glycemic index, while people with pre or full-blown diabetes are better off if they concentrate on low GI foods.

People with diabetes cannot produce enough insulin that would normally help to reduce blood sugar levels, which means they are more likely to have an excess of blood glucose that can damage the body. The slow and steady release of glucose in low-glycemic foods is helpful to keep blood glucose under control.

The glycemic index shows us part of the picture, but it doesn’t give any indications of how high your blood sugar could go when you eat the food, which is partly determined by how much carbohydrate is in an individual serving of food. A separate value called glycemic load does that. It gives a more accurate picture of a food’s real-life impact on blood sugar.

The glycemic load (GL)
The glycemic load (GL) is worked out by multiplying the grams of carbohydrates in a serve by the glycemic index, then dividing by 100.

A glycemic load of 10 or below is considered a low glycemic load (GL), 20 or above is considered a high GL. Watermelon, for example, has a high glycemic index of 80 because it can get into the blood quickly, but it has so little carbohydrates (6 grams per 100g) that its glycemic load is only 5 for a 100g serve.

The aim is to not only have low GI foods, but also to keep your glycemic load below 100 for the day.

Understanding digestion and carbohydrate absorption
The digestive system breaks down carbohydrates from our food and drinks into simple sugars such as glucose and fructose. For example, a soft drink/soda or a serve of rice will all be broken down to glucose in your digestive system, which is then carried to each cell through the bloodstream at different rates.

The pancreas secretes a hormone called insulin, which helps the glucose go from the blood into the cells. Once inside a cell, the glucose is ‘burned’ as fuel along with oxygen to produce the energy we need to run our brain, muscles, nervous system and much more.

The body converts excess glucose from food into glycogen which is stored within our muscles and liver to be used as needed between meals or during physical activity.

The quantity of carbs you eat is important
The quantity of carbohydrates in the foods you eat can also affect your blood glucose levels. For example, a serving of whole grain gluten free pasta is low GI, but still results in a high total amount of carbohydrate and hence will have a high GL.

GI and exercise
Eating low GI foods two hours before an endurance event, like long-distance running, is said to improve exercise capacity as it will slowly release energy for the following few hours after eating, but still be low enough in the digestive system to not make you gluggy or feel like vomiting.

This can vary from person to person as some cannot exercise for several hours after eating without feeling like regurgitating. On the other hand, high GI foods are usually recommended during the first 24 hours of recovery after an event to rapidly replenish glycogen, the sugar stored in our muscles, but this too is an individual situation and is not recommended for diabetic athletes. In fact, diabetes and athletics generally don’t go well together – but there can be exceptions.

GI Foods

High GI foods can be influenced by low GI foods
Eating low GI foods and high GI foods at the same meal can ‘average’ out the GI effect of the meal. This is important to understand, because most foods are eaten as part of a complete meal, which can totally change the GI value of foods.

Let’s say you ate a meal of fish and salad (low GI) with a dressing including honey (high GI) then the low GI foods would negate a quick release of sugar into the blood. So the idea is to have more low GI foods than high GI foods on the plate, or another way of saying it is, if you must have high GI foods, then have them with plenty of low GI foods.

Some GI scale examples

Low GI foods with a rating of less than 55: lentils, quinoa, grainy bread, soy products and beans.

Medium GI foods with a rating between 55 to 70: basmati rice, wholegrain gluten free bread, honey, and orange juice.

High GI foods with a rating higher than 70: white bread and short-grain white rice and white potatoes

Factors that affect the GI of a food

  • Factors such as the size, texture, viscosity, and ripeness of a food affect its GI. For example, an unripe banana may have a GI around 30, but as it gets ripe the GI can increase to 50 or more.
  • Fat, protein, and soluble fibre also generally lower a food’s glycaemic response. Foods like vinegar, lemon juice or acidic fruit such as lemon or limes can slow the rate at which the stomach empties and slows the rate of digestion, resulting in a lower overall GI effect on the meal.
  • Phytates, also known as Phytic acid which plants use to store phosphorus, are found in wholegrain breads and cereals, and delay a food’s absorption, thus I don’t recommend them for your diet even though they may be low GI.
  • Cooked foods and foods that have been processed can also affect the GI. But in saying this, I do not recommend processed foods at all for a healthy diet. I also suggest to occasionally eat raw foods and avoid overcooking meals when possible, such as lightly stir frying or steaming vegies so they are nice and crisp (which I find that kids generally enjoy more than limp vegies).
  • Food that is broken down into fine or smaller particles, such as a smoothie, puree or soup will be more easily digested and absorbed, which has the effect of increasing the GI.

Tips for healthy low GI eating

  • Use a breakfast muesli based on nuts, seeds, or whole grains such as quinoa or rice bran
  • Use grainy gluten free breads such as those with quinoa, chia seeds or other seeds
  • Enjoy a range of fresh whole fruit and vegetables
  • Eat plenty of salad vegetables with a dressing of lemon or lime juice with extra virgin olive oil dressing
  • Eat a variety of carbohydrate containing foods. Try carbs such as lentils, legumes, basmati rice, GF pita breads or GF pasta instead of normal white bread, white wheat pasta, and potatoes
  • Reduce serving size of foods, rather than just focusing on the GI rating.

Who should eat low GI foods?
We all need to watch the GI of our day-to-day diet, but there are a few groups that it’s essential for, such as:

People with diabetes
Diabetics can’t control their blood sugar levels very well, so a healthy low-GI diet can help to keep blood sugar levels under control.

People with pre-diabetes
This is where your blood sugar is higher than normal, but not high enough to be classified as diabetes. Low GI food choices can improve blood sugar levels and reduce your risk of developing diabetes.

People who are overweight
There’s some evidence that lowering the overall GI of your diet by eating low GI foods may help you lose weight. However, some foods that are low GI could be high in calories/kilojoules, so don’t rely on GI value alone.

People with high cholesterol and heart disease
There is some good evidence that low GI diets may help improve heart disease.

People with hypoglycaemia
Use low-GI foods for snacks as they produce a less dramatic and more sustained blood sugar release which is useful for between meals.

Everyday foods and the glycemic index

Potatoes aren’t all created equal. Most potatoes have quite a high GI, with Desiree and Pontiac potatoes right up near the top of the GI scale. But the ‘Carisma’ potatoes have a lower GI, with a rating of only 55.

Pasta (including Gluten Free varieties)
When starchy foods are cooked the starch grains absorb water. This makes it easier for the body to get to the starch, and the higher the GI.

Different varieties of rice contain different types of starch, which is why jasmine rice is a very high GI, while basmati and other varieties of rice are high in amylose starch which have a medium GI rating.

Breads (including Gluten Free varieties)
Breads are mostly high GI. In both the regular white variety and even wholemeal breads, the grains are ground down with the outer coating of the grain broken so the digestive enzymes can breakdown the starch easily.

Very grainy multigrain bread and gluten free sourdough loaves are lower in GI due to the acidity of the sourdough and full grains of grainy bread. But at the end of the day these foods can still be an issue for most people – and have a high GL due to the high carb factor.

Most vegetables, except the starchy vegetables like potatoes, carrots, parsnips, sweet potato, pumpkin, and corn (which are quite high GI) don’t contain much carbohydrate, so their GI and GL are quite low.

Sugar, with a 65 GI score, is actually only medium GI. This is because each molecule of table sugar (sucrose) is made up of one molecule of glucose (which contributes to the GI) and one molecule of fructose. The fructose heads straight to your liver for burning as an ‘instant fuel’ and doesn’t change your blood sugar level unless eaten in excess.

Even though foods that contain sugar have a moderate GI, they are still not good foods choices as they add heaps of calories/kilojoules with little or no valuable nutrients and can still have an overall high GL effect on the body.

Fresh fruit is generally low GI, although a few such as cherries, apricots, pineapple, and rockmelon are medium range. The notable exception is watermelon, which has a high value, but a low GL. Dried fruits are mainly low or medium.

What can affect the GI of foods?

Any process that changes the form of the food may contribute to changes in GI. Cooking and processing foods can raise the GI because digestion is then quicker. Cooked pasta for example has a higher GI than raw (not that you would want to eat raw pasta). Fruit juice generally has a higher GI than a piece of fresh whole fruit.

Food combinations
GI values that you see written in tables are based on blood sugar levels for each individual food. However, many foods are eaten in combination with other foods, which can create a variation of the effect on blood sugars.

If you consume carbohydrate-based foods with other foods that are high in fibre, fat or protein, the overall GI of the meal may be reduced, but the meal may still end up producing a medium glucose response.

Not all low GI foods are healthy

Chocolate and ice cream both have a low GI, but they are not healthy foods and should only be eaten very occasionally. Even though these foods have lots of sugar in them, their high fat content slows the digestion time and results in a lower glycemic response. However, they are high in calories and fat which will contribute to weight gain and lifestyle diseases. Some high GI foods that provide valuable nutrients, such as fruits, should not be completely excluded from the diet purely based on their GI.

Factors to consider with a low GI diet

Eating a diet that is low GI does not take into consideration other factors that may contribute to poor health or weight gain. GI is only a measure of the effects of carbohydrate-based foods on blood sugar levels and does not account for unhealthy foods that may contain little or no carbohydrate.

When choosing the best diet for your health, it is important to consider factors such as the fat, fibre and protein content, calories, portion size, and the value of the fibre, vitamins, and minerals they offer.

Tips to make a low GI diet work for you

  • Control the portion size of both high and low GI foods. Low GI foods can still have loads of calories, and even healthy choices can create weight gain if you eat too much of them.
  • Combine low and high glycemic index foods in the same meal or snack. Adding low GI foods helps to bring down the total glycemic index load of the meal. Adding some fat or protein to the meal also brings the score down, but don’t fool yourself into thinking that you can load up on fats if you eat a low GI diet.
  • Eat plenty of fruits and vegetables, even those with higher GI scores, as most fruits and vegetables are highly nutritious, and rich in fibre which helps to regulate blood glucose levels.
  • Add plenty of gluten free whole grains, legumes and beans to your diet which are generally low GI and supply protein as well as fibre.
  • Buy unprocessed, unsweetened, and unrefined food. Natural foods are always better for you – no matter what the GI is.
  • Replace snack foods that contain empty calories with nutritious snacks that are naturally sweet, such as fruit.
  • Use the Glycemic Index only as a guideline for your food choices and don’t obsess over the numbers. It is important to be eating a well-balanced diet that includes a variety of healthy foods, regardless of their GI scores.
  • Keep in mind that the glycemic load (GL) also makes a difference to how your meal affects your body.


Before you commence your diet, see your medical or health care professional for qualified guidance about what foods and supplements are best for your body. While on the diet do not stop any medications or supplements previously prescribed unless advised otherwise by your medical or health care professional.

During the early stages of a new diet, you may experience symptoms such as fatigue, headaches, or body aches, which may occur because your body is detoxifying. However, if you are unsure about a symptom at any time, check immediately with your medical or health care professional.

Case study: Low GI diet for dysglycaemia control

Client name and identifying information changed

Amanda wasn’t what you call sick, but she was a little overweight. Her main issue was that she would get loads of hypoglycaemia (low blood sugar) attacks that would leave her feeling wobbly, fatigued, with poor concentration and often emotional.

Amanda’s diet was all over the place; some days were good when she ate protein and salads or vegetables, and other days she would only eat carbs and then feel terrible for the next two days. This had been her roller coaster diet pattern for the previous 10 years or so.

On the days that Amanda ate loads of carbs her emotions were all over the place and she would get blood sugar irregularities – ‘low sugar attacks’ that gave her the above symptoms. When she felt this way she knew she needed to eat something sweet. It was an inbuilt mechanism of knowing what she needed to do to remedy the situation.

When we discussed how the body responds to sugar/carbs by releasing insulin to counter the surge of sugar in her blood, Amanda finally understood what was going on.

Amanda wasn’t previously aware that the way she started each day affected what she ate and how she responded for the rest of the day.

If she ate a sweet breakfast of toast and jam, or pancakes with maple syrup and fruit with coffee and sugar, then she would get the hypo attacks a couple of hours later.

This sent her into a frenzy, needing something sweet to counter the attack, or so it seemed, but of course this just spiked her blood sugar again, creating another spike in insulin and then another dump where she would feel terrible and had to eat carbs again.

It wasn’t until she ate a good protein-based meal for dinner that she would settle down and feel normal again but would be very tired from the stressful ups and downs during the day.

Amanda’s sleep was also affected by what she ate during the day, so she would wake tired and start the whole process again, needing something sweet to ‘kickstart’ the morning and then off on the roller coaster ride of carbs/sugar with spikes and drops.

On weekends she usually slept in and then eat a meal such as eggs and salad or eggs and bacon for breakfast and feel quite normal and stable all day.

Once this was brought to Amanda’s awareness the ‘penny dropped’ and she understood the mechanisms behind how she felt. She thought that she just felt good on weekends because she could sleep in and be more relaxed – but had not related how she felt to what she ate.

With her new awareness, Amanda chose foods that were more stabilising for her blood sugars. By eating low GI foods at the beginning and during the day, Amanda’s energy improved, her moods stabilised, she avoided the blood sugar attacks and feeding frenzies, and had better control of her weight in the process.

By changing her dietary patterns, it didn’t take long for Amanda to feel great.


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