Summary

  • Carbohydrates are essential for a healthy body and should not be removed from the diet.
  • Carbohydrates are the body's preferred energy source. The Australian Dietary Guidelines recommend 45–65% of energy needs to come from carbohydrates.
  • Choose better quality, wholegrain carbohydrates over refined carbohydrates.
  • A very low-carbohydrate diet combined with very high protein intake is not recommended.
  • Very low-carbohydrate diets tend not to lead to long-term weight loss.

Do we need carbohydrates in our diet?

Carbohydrates are essential for a well-balanced diet and healthy body. They are the body’s preferred energy source and fuel  vital organs – including the brain, central nervous system and kidneys. 

Carbohydrate is also an important energy source during exercise.  The digestive system breaks down carbohydrates into glucose and the pancreas secretes a hormone called insulin to help glucose move from blood into the cells.

Eating a potato, a bowl of pasta, or any type of carbohydrate-rich food won't automatically make you fatter. In fact, the Australian Dietary Guidelines recommend 45–65% of energy needs to come from carbohydrates.

Which foods contain carbohydrates?

Carbohydrates are found in a variety of foods, including:

  • grains
  • legumes (or beans)
  • dairy
  • fruit
  • starchy vegetables (such as potatoes, sweet potato, beans, corn)
  • processed or refined foods (such as white bread, white rice, hot chips)
  • sugary sweets (such as biscuits, cakes and lollies).

Some carbohydrates are healthier than others. Carbohydrates with lower glycaemic indexes (or GI) have a slower and flatter blood glucose response. They take longer to digest and can help us feel full. Lower GI foods are less refined (or processed) such as wholegrains, legumes and fruit.

What is a low-carb diet?

Low-carbohydrate (low-carb) diets are popular because they are based on claims that carbohydrates cause weight gain.

Although there are different variations, essentially low-carb diets restrict carbohydrate foods and replace them with foods usually high in protein and fat to lose weight.

There are many unhealthy misconceptions about weight loss and the claims that carbohydrates can make you fat are misleading.

Weight gain comes from an excess in overall kilojoules (or energy), which can come from any food source – including foods lower in carbohydrates and higher in dietary fat or protein.

Typical foods eaten on a low-carbohydrate diet include – beef, chicken, bacon, fish, eggs, non-starchy vegetables, and fats (such as oils, butter and mayonnaise).

Foods that are restricted include – many types of fruit, bread, cereals and other grains, starchy vegetables and some dairy products (other than cheese, cream or butter).

Restricting certain foods can affect your weight

If you are on a low-carb diet, and cutting out large groups of vegetables, fruits and grains, you may not be getting enough vital nutrients to manage your weight effectively. These types of diets can increase your risk of micronutrient deficiencies and constipation because of their low fibre content.

The Australian Dietary Guidelines suggests there is a likely link  between eating 3 to 5  serves of grain (cereal) foods each day (mainly wholegrain) and reduced risk of weight gain.

To maintain a healthy weight, combine a balanced diet with daily exercise. A recommended healthy diet includes:

Risks of low-carb diets

Very low-carbohydrate diets are unlikely to meet your daily nutritional needs.

Advocates of these diets advise people to consume kilojoules mainly from protein and fat sources – often recommending eating less than 100g of carbohydrate each day.

Many health professionals do not support these diets as they can have a high fat content (particularly saturated fat) and restrict important nutrients.

Very low-carb diets tend to restrict healthy food choices and may be:

Short-term health effects of low-carb diets

Initially, low-carbohydrate diets may contribute to rapid weight loss because they restrict kilojoules or energy.

The body begins to use stores of glucose and glycogen (from the liver and muscles) to replace the carbohydrates it is not getting from food. Around 3g of water is needed to release 1g of glycogen. Any weight loss at the beginning of a low-carbohydrate diet is mostly water, not body fat.

As carbohydrate stores are used up, the body begins to rely on other sources of fuel such as fat. This can lead to the development of ketones in the body, which can make the body acidic. It can also  contribute to metabolic changes, which may be dangerous for some with certain conditions (such as diabetes).

Symptoms that may be experienced from a low-carbohydrate diet, include:

Long-term health effects of low-carb diets

The long-term health effects of a diet very low in carbohydrates but high in saturated fat is still uncertain. Further research is needed to determine the safety of these diets.

Possible long-term effects may include:

  • Weight gain – when a normal diet is resumed, some muscle tissue is rebuilt, water is restored, and weight quickly returns.
  • Bowel problems – restricted intake of antioxidants and fibre from fruits and vegetables can increase a person’s risk of constipation.
  • Dieting problems – such as the ‘yoyo’ effect (where people lose and regain weight many times over a long period, rather than sustaining weight loss).
  • High cholesterol, obesity and obesity-related disorders – diets high in protein and fats are associated with conditions, (such as heart disease, diabetes and cancer). This can occur if the you have a diet high in fat, especially from fatty and processed meats (such as salami, sausages and bacon).
  • Kidney problems – can occur in people with impaired kidney function or diabetes.
  • Osteoporosis and related conditions – due to loss of calcium from the bones.

Healthy way to lose weight

A healthy diet high in fruits and vegetables, wholegrains, legumes and low-fat dairy products, and moderate in fat and kilojoules balanced with daily physical activity, is the best way to lose weight and keep it off.

Vegetarians and people who consume generally plant-based diets are generally slimmer and have much lower rates of obesity, heart disease and cancer, than those  who eat meat. This supports current thinking that diets high in unrefined carbohydrates help to maintain a healthy weight.

Watch your energy (kilojoule) intake

Ultimately, to avoid weight gain, energy intake should not be more than energy output.

Avoiding large portion sizes and limiting intake of saturated fats and added sugars will help to keep your energy intake in check.

Regular exercise is also critical for long-term weight loss success.

If you are not sure where to start or finding it difficult to manage your weight,  seek help from a dietitian. Dietitians can guide you to a healthy way of eating that is based on the latest research and tailored to suit your health and lifestyle. 

What foods meet our nutritional needs?

For most adults, suggested daily serves may include:

Recommended servings  One serve is equivalent to 
4-6 serves of grain (mostly wholegrain) foods  • 1 slice of wholegrain bread
•  ½ cup of cooked porridge
• ½ a cup of cooked grains (such as pasta, brown rice, quinoa, polenta)
 
2 serves of fruit 

• 1 apple, orange or banana
• 1 cup of canned fruit (no added sugar)
• 4 dried apricot halves (dried fruit should only be consumed sometimes because it is a concentrated source of sugar, increasing risk of tooth decay)            

5 serves (women) or 6 serves (most men) of vegetables. • 1 cup of salad vegetables
• ½ cup of cooked dried beans or legumes
• ½ a potato
• ½ cup of other cooked vegetables (broccoli, spinach, carrots)
2½ serves of milk, yoghurt, cheese and alternatives   • 1 cup of milk
• 2 slices (40g) of cheese
• 1 small tub (200g) of yoghurt
2-3 serves of meat or meat alternatives • 65g cooked lean beef, lamb, veal or pork
• 80g cooked chicken
• 100g cooked fish
• 1 small can of fish
• 2 large eggs
• 1 cup of canned beans
• 170g tofu
• 30g nuts or seeds

Select carbohydrates, proteins and fats carefully

If you choose to follow a low-carbohydrate diet, do not avoid carbohydrates completely – you need some in your diet for fuel and to metabolise fat.

Choose carbohydrate-rich foods that are unrefined or unprocessed (including wholegrains and fruit), rather than refined and energy-dense forms (such as cakes, sweets and soft drinks). Have a variety of vegetables daily.

Select a variety of protein-rich foods that are also low in saturated fat, for example:

  • lean cuts of red meat
  • fish (including fatty fish)
  • lean chicken and pork.

You could also select protein-rich foods that are plant based, for example:

Choose healthy unsaturated fats from plant sources (such as, olive, canola, peanut or soy oil) rather than from animal sources (butter or meat fat).

Where to get help

References

More information

Weight management

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This page has been produced in consultation with and approved by: Deakin University - School of Exercise and Nutrition Sciences

Last updated: December 2020

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