Glycaemic Index

CHOICE investigates whether our national waistline can benefit from new research on the glycaemic index.
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  • Updated:2 Jun 2009

01.What is GI?

Low GI food

In brief

  • Low-GI diets have been shown to help people with diabetes and pre-diabetes, but they may also help those who need to lose weight.
  • Low-GI foods aren’t necessarily healthy in themselves, so look for healthy foods that also happen to be low GI.

The Glycaemic Index (GI) is a measure of how the carbohydrate in a food affects your blood glucose levels as it’s digested, absorbed and metabolised. If this happens quickly, there’s a rush of glucose into the bloodstream followed by a quick fall – the food is higher in the GI scale. If it gives a slower and gentler rise and fall in blood glucose, the GI is lower.

It’s a way of ranking carbohydrates and their effect on blood sugar, by comparing their effect against pure glucose. It’s this slower rise and fall in blood sugar that has led to claims low-GI foods give you longer-lasting energy – they keep blood sugar at a moderate level for a longer time than the sharp peak and fall of high-GI foods. Don’t confuse this with your personal energy levels or your get-up-and-go: the two things aren’t the same.

When CHOICE last visited this topic in 2004, a healthy, low-GI diet was thought to be most helpful for people with diabetes, but evidence has since emerged to suggest a much wider group of people may benefit, including those who need to lose weight. Not only are Australians getting fatter, but more importantly, it’s estimated as many as one in every four Australian adults has diabetes or pre-diabetes – both of which can be managed with a low-GI diet.

Please note: this information was current as of June 2009 but is still a useful guide today.

Who should be eating low GI?

  • Diabetes People with diabetes cannot control their blood sugar levels well. A healthy, low-GI diet has been shown to keep blood sugar levels under control.
  • Pre-diabetes This is where your blood sugar is higher than normal, but not high enough to count as diabetes. Since it’s only diagnosed by a glucose tolerance blood test, most people don’t realise they have pre-diabetes unless it develops into diabetes.
  • Low-GI healthy eating may improve blood sugar control and reduce the risk of developing the disease.
  • Overweight While not all experts are convinced, there’s evidence that lowering the overall GI of your diet by selecting low-GI foods may help you lose weight – see Can a Low GI Diet Fight Flab?.
  • Cholesterol and heart disease This is also debated, but there’s some good evidence low-GI diets may help improve heart disease risk factors.
  • Hypoglycaemia Many people may think they suffer from low blood sugar, but experts believe hypoglycaemia isn’t as common as people assume. Low-GI foods give a less dramatic and more sustained blood sugar release, so some people may find them useful to get them through between meals.

How to follow a healthy low-GI diet

The basics of healthy eating invariably include plenty of fruit, vegetables and wholegrain cereals; lean meats; fish a few times a week; watching the bad fats (saturated and trans) while getting in some of the good ones (nuts, seeds, olives, avocado); consuming low- or reduced-fat dairy foods; and going easy on salty and sugary foods.

So while GI isn’t the only factor to worry about, for many people it’s useful to finetune your healthy diet by swapping high-GI for low-GI carbohydrates. Choose a lower GI rice variety (such as basmati) or go for pasta instead; and swap white or wholemeal bread for a grainy seed bread. Of course, some foods – such as chocolate bars, ice-cream and cake – are not healthy choices, no matter how low their GI. Equally, you shouldn’t necessarily avoid otherwise healthy foods such as watermelon because of its high GI. As always, moderation is the key.



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