What is a kilojoule ( kJ )?

In Australia, we use kilojoules as a measure of energy.  Energy used to be measured in calories and sometimes still is.  One calorie is equal to 4.2 kilojoules.

We can measure or estimate the amount of energy (or fuel) our bodies use and how much energy is in food and drink. If we eat and drink fewer kilojoules than our body burns, we will lose weight. For example, to lose half a kilogram of fat, or ‘weight’ we need to consume about 2,000 kJ a day less than we use. If we consume more kilojoules than we use we will store the extra energy as fat and gain fat or ‘weight’. If these values match we will maintain our weight. It’s all about the balance between energy (or kilojoules) in and energy (or kilojoules) out.

Sometimes 8,700 kJ per day is used as an approximate figure for the ‘average’ Australian to maintain their weight. This can be a rough guide and can be useful for knowing how much room the kilojoules in a portion of food, found by using the nutrition information panel on food packages, would take up in your meal and snack plan. However, people’s bodies use varying amounts of kilojoules, depending on their age or life stage, height, weight, sex and physical activity. The best guide to your own kilojoule needs is what your weight is doing.

Energy ( kilojoule ) balance

Our bodies burn kilojoules on normal everyday processes like breathing and pumping blood, but also on physical activity. To lose weight we can either use more kilojoules, or eat fewer kilojoules. The way to use more kilojoules, is to be more physically active. To lose weight successfully, most people find that they need 60-90 minutes of moderate intensity activity, like brisk walking, on most days. However, increasing everyday activity like taking the stairs instead of the lift, parking further away, or trying to sit for less time is very helpful too.

The Australian dietary guidelines will help you reduce the kilojoules that you eat and drink. Kilojoules can be reduced by swapping discretionary foods for foods from the five food groups, reducing portion size and avoiding extra serves. Eating and drinking less fat, added sugars and alcohol and more fibre and water helps too. Fat, sugar and alcohol have more concentrated kilojoules while water has no kilojoules and fibre in food makes it less energy dense. Even small changes are worthwhile. Just reducing the kilojoules we eat and drink by 100kJ a day will lead to one kilogram of weight loss over a year.

The NSW Food Authority has lots of excellent information about kilojoules.

How much exercise do I need?

The National physical activity guidelines (2010) recommend at least 30 minutes of moderate-intensity physical activity on most, preferably all, days. A good example of moderate-intensity activity is brisk walking, that is at a pace where you are able to comfortably talk but not sing. Other examples include mowing the lawn, digging in the garden, or medium paced swimming or cycling.

The National physical activity guidelines (2010) note that the recommended 30 minutes (or more) of moderate intensity physical activity throughout the day, may be accumulated by combining short bouts of around 10 to 15 minutes each. These accumulated short bouts of physical activity are as effective as continuous activity at improving indicators of health such as hypertension and blood cholesterol. However, this level of activity appears to be insufficient for preventing weight gain or weight loss or weight regain in most people.

The evidence reviewed for the Australian dietary guidelines suggests that a minimum of 45-60 minutes per day is required for both cardiovascular health and weight maintenance.

The Commonwealth Department of Health and Ageing are currently reviewing the National physical activity guidelines (2010) and these are expected to be released in 2013.

What are processed foods?

When people talk about processed foods they are often thinking of ‘discretionary foods’ which are usually made up of a number of ingredients, often have added fats, added sugars and/or added salt and may have fibre removed. The higher saturated fat, sugar and salt content and lower fibre of discretionary foods is linked with excess weight and some chronic disease. This means discretionary foods should be chosen with care and limited to occasional and small amounts particularly if you are aiming to lose weight.

However, strictly speaking ‘processed’ foods are any foods that have undergone a process, even cooking. Often foods need some sort of processing to be edible or palatable. For example grains need to be ground, cooked or rolled, such as for making bread and pasta.

Some types of processing means we can have a greater variety of nutritious foods in our meals and snacks. For example, vegetables canned without salt, or frozen can give us more long shelf life options for quick and easy meals that include vegetables. Milk processed into yoghurt and packaged into snack size packages is a healthy, portable easy snack for lunchboxes or when travelling.

Processing can also make some foods better for us, like low fat and skim milk, where saturated fat has been removed.

So we don’t need to avoid all processed foods, but rather to focus on those that still contain all the fibre, like whole grains, whole fruits and vegetables, and avoid those where the fibre has been removed such as white bread and fruit and vegetable juices. We also need to be aware of processed foods when saturated fat, sugars or salt has been added and use food label reading skills to make better choices.

Fibre - why do we need it?

The Australian dietary guidelines encourage us to eat more foods high in dietary fibre like vegetables, especially legumes, fruit and wholegrain foods. We know that fibre is great for health, helps prevent many chronic diseases and helps us control our weight.

Fibre is only found in foods from plants. It is the part of what we eat that doesn’t get digested in the small intestine and so continues into the large intestine where it is helpful for good health in many ways.

Most of us don’t eat enough fibre. Part of the reason is that we eat too many discretionary foods that tend to be low in fibre and they take the place of some of the serves from the high fibre food groups. By swapping discretionary foods for high fibre foods, making sure we eat vegetables or salad with two meals a day, using fruit for snacks and desserts and adding legumes to our recipes we can make a real difference to our fibre intake.

There are three main types of fibre that help us stay healthy in different ways and avoid problems, and we need plenty of all three.

Insoluble fibre

Insoluble fibre is particularly good for our digestive systems. It is bulky and absorbs water so it fills us up for few kilojoules, keeps stools soft and bulky and our bowels regular. It also helps prevent some problems with our bowel like diverticular disease, haemorrhoids, constipation and bowel cancer.

Foods high in insoluble fibre are wholegrain breads and cereals, fruit and vegetables (especially the skins), and nuts and seeds. However, while vegetables and fruits are lower in kilojoules than many other foods, nuts and seeds are high and people aiming to lose weight still need to keep serve sizes small.

Soluble fibre

Soluble fibre works differently. It still makes us feel fuller but also helps people manage their blood cholesterol and blood glucose. High soluble fibre foods include fruits, vegetables, legumes, barley and oats.

Resistant starch

When resistant starch travels undigested to the large intestine it is helpfully processed by ‘good’ bacteria and the byproducts help keep the bowel lining healthy. Foods rich in resistant starch include under ripe bananas, cooked potato that has been cooled and firm cooked pasta.

Source: Dietitians Australia (formerly Dietitians Association of Australia).