Kilojoules, calories and energy
Kilojoules and calories
Kilojoule (kJ)
The kilojoule is a measurement of energy. It can be used to work out how much energy we get from the food we consume or how much energy we expend when we exercise.
Calorie (kcal)
Calories are another measurement of energy. One calorie is equal to 4.18 kilojoules. Many people think that energy is good while calories are bad. But really, one is just a measure of the other.
Just how many calories do I burn?
If you’re of average size, when at rest, you use energy at about 1,500 kcal a day. This is equivalent to 1 kcal a minute.
An average person is thought to eat about 2,000 kcal a day.
If you stand up, your body’s energy requirement increases by about 20% to say, 1.2 kcal a minute.
If you walk slowly at 2 km/hour this will double your energy output – 2 kcal a minute.
Walking at 4 km/hour uses four times as much as resting, ie 4 kcal a minute. Now you’re reaching moderate physical activity – which means that you’ll start to have health benefits even if you don’t lose weight!
The World Health Organisation recently recommended one hour (60 minutes) of moderate activity every day to improve health and prevent obesity. You don’t have to be active all at one time – a few minutes here and there all add up over the day.
- Take the stairs instead of using the lift
- Park the car further away from your destination and walk
- Have meetings walking in the corridor
- Stand up and walking around while talking on the phone
Fuelling the body
Although we need energy to function, an energy-dense diet will promote weight gain. You need a healthy balanced diet combined with exercise. See below for some examples of how much energy is in different foods and which foods you should eat in moderation only.
Energy density relates to the amount of fat, sugar and water in a food.
Food sources and energy density
One avocado (150g) contains 22g of fat, 30% of the average daily fat requirement (but is a good source of fibre).
One meat pie (170g) contains 32g of fat, 40% of the average daily fat requirement.
Soft drinks contain 11g of sugar per 100ml. A can is 340ml which is 8tsp of sugar.
Milk shakes contain 25g of sugar per 100ml. A 300ml shake (usual serve) contains 15tsp of sugar.
Fruit juice and cordials contains 10g of sugar per 100ml. A 250 ml drink (usual serve) contains 5tsp of sugar.
