The low GI diet favours certain carbohydrate foods over others and was originally designed for people with diabetes but is also promoted for weight loss.

Carbohydrate is a major component of many foods.

Foods that contain carbohydrates include grains (bread, breakfast cereals, rice, pasta, biscuits, cakes), legumes, fruit, vegetables (especially sweetcorn, potato), milk and yoghurt, confectionery, and added sugars.

Are some carbohydrates better than others?

When we digest food, the carbohydrates in them are broken down into simple sugars, mainly glucose.

The Glycaemic Index (GI) is a rating based on how rapidly the carbohydrate in a particular food is digested to glucose and absorbed into the bloodstream compared with pure glucose.

Carbohydrate foods with a low GI can provide a slower, steadier rise in blood glucose levels (the source of much of our energy).

This should give sustained energy and, hopefully, help us feel full for longer.

Foods with a high GI may cause blood glucose levels to spike — useful if you're about to undertake some physical activity, but if the high GI food is eaten on its own, the spike may be followed by a drop in blood glucose that could promote more eating.

Foods can only be assigned a GI value if they contain carbohydrate.

Meats, poultry, seafood, eggs, cheeses, and oils have no carbohydrate and some vegetables have too little carbohydrate to be given a GI value.

How does the low GI diet work?

The diet replaces high-GI carbohydrate foods with low-GI alternatives.

Low GI diets designed for weight loss also recommend meals and snacks that have fewer kilojoules than the usual diet.

Dieters divide their meals into one-quarter low-GI carbohydrate foods and one-quarter protein foods with the remaining half made up of fruit and vegetables.

The golden rules of this diet are:

Seven or more serves of fruit and vegetables a day;

Seven or more serves of fruit and vegetables a day; Low-GI breads and grain-based foods;

Low-GI breads and grain-based foods; More legumes, nuts, and seafood;

More legumes, nuts, and seafood; Lean meat sources;

Lean meat sources; Low-fat dairy products.

Low-GI carbohydrates (a GI rating of 55 or less) include most fruits, milk, yoghurt, legumes, vegetables such as peas and corn, genuine sourdough, wholegrain or multigrain breads, oats, barley, pasta, quinoa and some types of rice (for example basmati, Doongara).

High-GI carbohydrates (70-plus) include jasmine rice, most potatoes, most white bread, bagels, and most highly processed snack foods (such as biscuits and most crackers) and confectionery.

Sample low-GI menu

Breakfast: Muesli with yoghurt and fruit.

Snack: A piece of fruit, such as an apple.

Lunch: Wholemeal pita bread, falafel, hummus and tabouleh.

Snack: Carrot and celery sticks.

Dinner: Stir-fried prawns, vegetables, and Hokkien noodles.

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What do experts think of a low GI diet?

If you want a healthier diet, choosing better-quality foods, including healthy sources of carbohydrate, can help.

Low-GI carbs may have additional health benefits for those with type 2 diabetes.

For weight loss, research on low-GI diets is mixed. Some studies show a small benefit but many show no effect.

However, as most low-GI diets don't restrict any major food groups, they are likely to be nutritionally balanced.

The role of the GI in healthy eating is often misunderstood.

Some important points to consider are:

You shouldn't consider the GI in isolation.

You shouldn't consider the GI in isolation. Some foods with a low GI may be high in saturated fat or have little nutritional value, for example fructose (fruit sugar), soft drinks, cakes and ice cream may have a low GI but have little place in any weight-loss diet.

Some foods with a low GI may be high in saturated fat or have little nutritional value, for example fructose (fruit sugar), soft drinks, cakes and ice cream may have a low GI but have little place in any weight-loss diet. Also, if you choose foods with a high GI, such as potato, including a low GI food, such as pears will provide balance in that meal.

You still need to watch your overall kilojoule intake.

If you simply change jasmine rice for basmati, and white bread for wholegrain, or consume large bowls of pasta with a rich sauce, the kilograms are unlikely to budge.

Remember to consult your doctor before starting any new eating plan if you have an underlying health condition or history of an eating disorder.

This is general information only. For detailed personal advice, you should see a qualified medical practitioner who knows your medical history.

This story, which was originally written by Pamela Wilson and published by ABC Health and Wellbeing, has been reviewed by Dr Rosemary Stanton OAM, nutritionist and visiting fellow, School of Medical Sciences, University of NSW, and updated in 2019.