Low-GI foods: How the glycaemic index affects your carbs

If you find yourself in the bread aisle of the grocery store and feel like you need a food science degree to pick a loaf, you wouldn’t be alone.

Whether you’re reading low FODMAP or low GI, the acronyms and abbreviations can leave even the most nutritionally-minded among us confused, but understanding what these terms mean is important because they can impact the choices you make about your diet, particularly if you’re trying to lose weight.

The glycaemic index, also known as GI, might even be something you've heard of before in the context of diabetes management, but low glycaemic foods can offer some health benefits beyond that.

So, let's look at what the glycaemic index is, what its relationship is to carbohydrates, and how it can (and can't) help you in your healthy eating plan.

What is the glycaemic index (GI)?

When you eat food or drink liquids, your body breaks them down into carbohydrates, fat, and protein in order to use them. While all of these serve different, vital functions, carbohydrates are one of the most important as they are your body’s preferred source of energy [2].

The glycaemic index (GI) is a way of sorting these carbohydrates based on how quickly they can raise your blood sugar levels [1], making it a vital way of understanding both digestion and how our bodies give us energy.

What are low-GI foods?

Low GI foods are foods that contain carbohydrates that break down slowly, releasing glucose into your bloodstream at a slower and flatter rate. This helps to prolong digestion and has been found to help you feel fuller for longer, potentially aiding you in maintaining a healthy diet.

By comparison, high GI foods contain carbohydrates that break down fast and raise your blood sugar quickly, making them particularly important to track for people with diabetes [2].

What makes a food ‘low’ vs ‘high’ GI?

The glycaemic index is often discussed on a three-category scale: low GI, medium GI and high GI.

Low GI foods such as oats and lentils contain a GI level of less than 55, while medium GI foods such as honey and whole grain bread contain a GI score between 55 and 70, and high GI foods such as white bread and potatoes contain a GI level of over 70.

Understanding the GI value of food can help you understand how the food can contribute to feelings of fullness and energy levels.

Low-GI food list

Low GI foods include:

• Most fresh fruit and vegetables, particularly starchy vegetables like sweet potatoes, sweet corn, raw carrots and beans
• Legumes such as lentils, chickpeas and kidney beans
• Whole or steel-cut oats; and
• Unsweetened and low-fat dairy

High-GI food list

High GI foods include:

• White bread and bagels
• White rice
• Rice cakes and most types of crackers
• Cakes, doughnuts and pastries
• Most types of fruit juice
• Most packaged breakfast cereals; and
• Potatoes

Is a low-GI diet good for you?

A low-GI diet can be a great way to monitor your blood sugar levels, but there’s more to a healthy diet than that, especially considering some low-GI foods are also processed foods and high in saturated fats, such as chocolate and ice cream.

Taking a holistic approach to healthy eating is always better than limiting yourself to any one particular type of diet, and you can do this by considering not just a meal’s GI, but:

• The total number of kilojoules
• The protein and dietary fibre content
• The sodium and saturated fat content, and
• Any added sugar [1]

Having a rounded diet that includes a variety of foods from all five food groups is vital not just for weight management but your broader health, like your blood pressure and cholesterol levels.

Does eating low-GI foods help with weight loss?

While it’s long been hypothesised that low-GI diets can promote weight loss and decrease the risk of obesity, numerous studies have found that it has a pretty minimal effect on weight loss, if they do at all [4]. In other words, while it might help with your blood sugar levels and keep you feeling fuller for longer, it’s unlikely to help with the number on the scales.

What is glycaemic load?

Like any meal, how much you consume is as important as what you consume. You might grab some low-GI wholegrain bread rolls to go with your soup for dinner, but eating three of them will still cause your blood glucose levels to rise more rapidly than if you had one. This is called the glycaemic load (GL).

The idea, as a result of the glycaemic load, is that smaller portions of high-GI foods will have the same impact on your blood glucose levels as a larger portion of a low-GI food, making the benefits of eating foods with that low glycaemic index pointless.

As a result, calculating how much GI is in what you’re eating is essential if you want to follow a low GI diet [2].

How to calculate glycaemic load

Luckily, there’s a pretty straightforward way to do that. The GL calculation is a matter of multiplying the GI by the amount of carbohydrates (in grams) in a serving of food and dividing it by 100.

The Victorian Department of Health offers a clear example with white wheat pasta on their website:

• GI of a standard white wheat pasta, boiled to al dente texture = 43
• The carbohydrate content of a standard 180g serve = 44g
• GL = 43 x 44/100 = 19g

If a half portion of pasta was eaten, though, the GL would also halve:

• GI of a standard white wheat pasta, boiled to al dente texture = 43
• The carbohydrate content of a half portion 90g serve = 22g
• GL = 43 x 22/100 = 9.5g [2]

If you're unsure what the GI content of what you're eating is, resources such as the University of Sydney's Glycaemic Index Research search tool can help you to navigate low GI carbohydrate foods and high glycaemic foods in a convenient, straightforward way.

Balanced, sustainable weight loss with Juniper

Sustainable weight loss and weight management are never about any one thing. It takes time, and a balance of making healthier food choices, committing to regular exercise, getting the recommended amount of sleep, and making holistic lifestyle changes that support your body to look and feel its best.

The Juniper Programme ensures you don't have to do this alone. Led by dieticians who can help you design meal plans based on nutritional quality, with medically-backed treatment and a community ready to offer advice and support, this program can help you to not just reach your body weight goal but maintain it long into the future.

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