A Guide to Carbohydrates

“Carbohydrate” is a word hot on everyone’s lips, and not usually in the friendliest sense. In fact, carbohydrates seem to be the latest evil scapegoat, blamed for everybody’s extra kilos. But the idea that carbs are somehow “bad” for you is unfounded, unwise, and misleading. Carbohydrate foods in their more natural forms are a very important part of a healthy diet. They provide energy, fibre, vitamins, minerals, protein and water, all of which are crucial for a fit and happy body.

Discover different types of carbohydrates and the roles they play in your body, learn how to incorporate carbs into your diet and find out whether carbs really are fattening…

What are carbohydrates?

Carbohydrate foods are an important part of any healthy diet.

In technical terms, a carbohydrate is an organic compound made up of carbon, hydrogen and oxygen atoms. In food terms, carbohydrates are found in many foods such as cereals, grains, fruit, legumes, fruit juices, vegetables, milk, sugars, jam, honey, confectionery and soft drinks.

At a rudimentary level, carbohydrates can be described as either simple or complex:

  • Simple carbohydrates are the most basic carbohydrates found in foods such as sugar, honey, jam, confectionery and soft drinks. These contain very little in the way of nutrients other than carbohydrates.
  • Complex carbohydrates come from plants, and are found in foods such as grains, breads, cereals, vegetables, legumes and seeds. Unlike simple carbohydrates, these foods contain other essential nutrients, such as vitamins, minerals and dietary fibre.

Technically speaking, however, carbohydrates are classified by the number of single sugar molecules they contain. All carbohydrates are made up of one or more basic sugar molecules binding together to form monosaccharides, disaccharides, and polysaccharides.


Monosaccharides contain just one sugar molecule. These are sugars in their most simple form. The most important monosaccharides are glucose, fructose and galactose.

Glucose Also known as dextrose or grape sugar. This is the major form of sugar in the blood and ultimately provides energy for all cells in your body. Your body converts the carbohydrates in your food to glucose. It’s also present in some foods such as honey.
Fructose Also known as fruit sugar or levulose. This is present in fruit and honey and in small amounts in vegetables.
Galactose This is formed during the digestion of milk sugar (lactose).


Disaccharides contain two sugar molecules joined together. The most important disaccharides are sucrose, lactose and maltose.

Sucrose This is made up of glucose and fructose. It’s found mainly in sugar cane. Small amounts of sucrose are found in some fruits and vegetables such as peaches, apricots, pineapple, peas and sweet corn.
Lactose This is made up of glucose and galactose. It’s the sugar naturally present in milk.
Maltose This is made up of two glucose molecules, and is found in malt and malted milk.


Polysaccharides can contain up to 10,000 glucose or sugar molecules linked together like a strand of pearls. The most important polysaccharides are starch and glycogen.

Starch This is found in legumes, grains and cereal products such as rice and wheat, and in vegetables, especially root vegetables such as potatoes.
Glycogen This is a carbohydrate form stored in your liver and muscles; it’s like a ‘savings bank’ of carbohydrates for your body. Glycogen stored in the liver is used to replenish blood sugar levels, particularly between meals. Glycogen stored in the muscles is the most readily-available source of glucose used for energy when you’re exercising.

What are carbohydrates for?

Carbohydrate foods provide your body with the energy it needs to carry out every day functions and more!

Carbohydrates play numerous roles in your body, and their importance cannot be overstated. Carbohydrates are like the building blocks for many of the body’s crucial functions, including:

  • Energy! The main function of carbohydrates is to supply your body with energy. Energy is necessary to keep you alive and active in body and mind. Carbohydrates are the most important source of energy for your body. Each gram of carbohydrate gives your body four calories of energy. Carbohydrates need to be supplied regularly and at frequent intervals in order to meet the energy needs of your body. Insufficient stores of carbohydrates in your body results in low blood sugar levels, which can lead to poor concentration and fatigue.
  • Protein-sparing effect. One of the most important jobs of carbohydrates is to allow protein to keep to its primary functions such as muscle, hormone, and enzyme building. Protein is considered an “expensive” form of body fuel because it has more important jobs to do than just providing energy. However, if there aren’t enough carbohydrates in your diet, your body is forced to convert protein to glucose to supply you with energy. If this process of “protein burning” continues for too long, your body eventually eats up muscle tissue along with body fat. Muscle supports your metabolism – the more lean muscle you have, the faster your metabolism should be. It’s also good to remember protein is used more efficiently when it’s eaten in tandem with carbohydrates. In other words, a sandwich with a lean meat filling is better than just eating lean meat on its own.
  • Fat metabolism. Carbohydrates are necessary for fat metabolism. If you’re eating insufficient carbohydrates, then your body relies on consuming larger amounts of fats than you’re equipped to handle for energy. Although the use of fats for energy might sound like a good idea to those wanting to lose weight, it results in ketosis. Ketosis disturbs your body’s normal acid-base balance. This can lead to the loss of sodium & fluids, causing dehydration and sodium imbalance. The ketones produced by ketosis are actually toxic substances which can cause headaches, nausea, lightheadedness, bad breath and body odour. Large amounts of ketones can lead to kidney damage; and even to coma and death for people with untreated diabetes.
  • Brain food. Carbohydrates are the primary and preferred source of energy for almost all of your brain. Without adequate carbohydrates, your body is forced into ketosis to feed your brain. Ketosis is sometimes claimed to help with rapid weight loss, but it has many negative side effects including problems with clarity of brain function.
  • The central nervous system. Simple carbohydrates in the form of blood glucose are also the main source of energy for your central nervous system. They alone maintain the correct functioning of the nervous system.
  • Red blood cells. Red blood cells can only use glucose and other simple carbohydrate forms for energy.

How many carbohydrates should you eat?

Carbohydrates are your body’s main fuel source and should therefore make up a large portion of your daily energy intake (calorie intake), mainly in the form of whole grains, vegetables, legumes and some fruit. Exactly how many carbohydrates you need depends on a number of factors, the most important being your daily calorie intake. At Food.com.au, we recommend around 45 – 65% of your total calories come from carbohydrates. Variations on this rule are shown in the table below.

Other factors also influence your recommended carbohydrate intake, such as:

  • Body weight. More specifically, the amount of body muscle. The greater your muscle mass, the more carbohydrates you need.
  • Gender. Males generally require more carbohydrates due to their greater muscle mass.
  • Training level. Elite athletes will have greater needs than a recreational athlete who goes to the gym three times a week. The more active you are, the more carbohydrates you’ll need.
  • Type of sport. Endurance-type sports, such as long-distance running, require more carbohydrates than “short-energy burst”’ sports, such as a 100-metre sprint. Any aerobic sport also requires substantial stores of carbohydrates.
  • Diabetes. Although most people with diabetes can include a moderate amount of carbohydrates in their diet, individual health will affect particular dietary needs.
  • Carbohydrate-sensitivity, grain allergies, digestive disorders. If you have any of these conditions, you may only be able to include a gradual and moderate amount of selective carbohydrates in your diet.

* You should discuss your recommended calorie and carbohydrate intake with your doctor or dietitian.

Daily Total Calories Daily Total Carbohydrates Percent of Carbohydrate Calories
1200 cals 120g 40%
1500 cals 170g 45%
2000 cals 250g 50%
2500 cals 345g 55%
3000 cals 450g 60%

From Allan Borushek’s Pocket Calorie, Fat & Carbohydrate Counter, 2005 edition.

Are carbohydrates fattening?

There’s so much confusion over whether or not carbohydrates are fattening. Some people say not to eat pasta, bread, or potatoes because they’re fattening, but others say you should eat more carbohydrates because they’re so good for you.

The truth is carbohydrates are an essential part of any diet. However, too much of anything, including carbohydrates, can be fattening. It’s best to develop a good understanding of how many carbohydrates you need so as to be sure you don’t eat too many or too few.

Here are some points to keep in mind when considering the relationship between carbohydrates and weight loss:

  • No carbs means no real weight loss. When you don’t eat carbohydrates, you break down your muscle tissue along with body fat. If you lose weight as a result of this, you also lose your muscle. And chances are, any weight loss caused from restricting carbs is actually due to water loss. When you start adding carbohydrates back into your diet, you quickly gain the weight back.
  • Food is a complex mixture of many nutrients, so it’s impossible to say just one type of food is fattening. The nutrients which provide energy are carbohydrates, fats and proteins, and most foods contain all of them. This energy is measured in calories or kilojoules.
Energy Values Per Gram of Food    
Carbohydrate 4 calories 17 kilojoules
Protein 4 calories 16 kilojoules
Fat/Oil 9 calories 37 kilojoules
Alcohol 7 calories 28 kilojoules

As indicated by the chart, different nutrients contribute a different amount of calories. Fats provide over twice as many calories as carbohydrates.

  • We usually eat carbohydrates and fat together. For example, spaghetti bolognese has a sauce made with oil and minced meat and is topped with cheese. These ingredients contain a lot of fat, and therefore contribute many calories. Pasta alone contains very little fat and is made up mainly of carbohydrates, which contribute fewer calories. This pasta meal is fattening more so because of the sauce than the pasta.
  • Too much of anything is fattening! If you eat too much of anything, it’s going to add excess weight. As a recent World Health Organisation report points out: “It’s important to state excess energy (calories) in any form will promote body fat accumulation, and excess consumption of low-fat foods, while not as obesity-producing as excess consumption of high-fat foods, will lead to obesity if energy expenditure (exercise) is not increased.” When more carbohydrates are eaten than is good for your body, most of them are stored in the liver and muscles as glycogen; the remainder is stored as fat.
  • Carbohydrates are more filling than fat. The fibre content of most carbohydrates swells in the digestive system, which makes you feel full faster than other foods do. Also, the conversion of dietary fat to body fat requires very little energy compared to carbohydrate conversion; in fact, only 3% of energy intake is required in this process. Compared to carbohydrates, it can be easy to eat too much fat because foods high in fat are generally low in dietary fibre; therefore it takes more of those foods for us to feel full.

Which carbohydrates are better for you?

When considering which carbohydrate foods to include in your diet, it’s best to think in terms of refined and unrefined carbs.

Those from the unrefined group make far better choices. Unrefined carbohydrates provide your body with energy for a longer period of time. They also keep your blood sugar levels stable, and provide fibre to support your digestive system. Foods high in fibre fill you up quickly and are generally harder to overeat.

Good sources of unrefined carbohydrates include whole grain bread, brown rice, beans, vegetables, nuts and seeds.

Refined carbohydrates provide short bursts of energy to your body. This may cause your blood sugar levels to spike and then drop, leaving you feeling hungry and drained again a short time after eating. It can be easy to eat too many refined carbohydrates.

Examples of refined carbohydrate foods include lollies, biscuits and soft drinks.

So don’t cut carbohydrates from your diet, but do choose wisely and stick to unrefined carbohydrates whenever possible. And as with all foods, watch your portion size!


This article was compiled in consultation with health experts and in reference to the following sources:

World Health Organisation, ‘Carbohydrates in Human Nutrition – Interim Report of a joint FAO/WHO Expert Consultation,’ 1997

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