What is Energy?

image: boy jumping

Energy is an incredible thing. You can't see it, touch it, smell it or hear it, yet it is used everyday by many things. Energy comes in many shapes and forms and can be used in many ways. The energy needed for a car is petrol, energy for a fridge or a washing machine is electricity. For us Humans,  our energy comes from the food and drinks that we consume. The unit of measure for this energy is usually expressed in calories.

What are calories?

Calories are a measure of how much energy food or drink contains.

The amount of energy you need will depend on:

  • your age: for example, growing children and teenagers may need more energy 
  • your lifestyle: for example, how active you are
  • your size: your height and weight can affect how quickly you use energy 

How is energy used in our bodies: Normally you think of using energy when you are running around, riding your bike or swimming - have you ever noticed how hungry you are after swimming? The more active you are, the more energy you will use. It is food and drink that gives you the energy you need for all this activity ! But what you might not think of is that what you eat and drink gives your body the energy it needs for the important processes of life, like breathing or growing. It even uses energy to keep your body temperature at just the right level.

Your body uses a lot more energy when you are very active, and less if you are sitting down or watching the television. It even uses energy when you’re sleeping as your body repairs and renews itself! When you exercise or play games, your heart and muscles  have to work much harder. Next time you're running or skateboarding, see what happens to your heart rate, breathing and temperature.

How much energy do you need every day?

Some people lead very active lives, exercise a lot and are not still except when they are sleeping. These people use a lot of energy so they need to eat more food to give them that energy.

Other people are not so active, preferring to read or watch TV. They need less food because they use less energy.

Energy requirements are related to age, gender, body size and level of activity. Therefore it is difficult to give recommendations for a general calorie intake. Energy requirements tend to increase up to the age of 15 -18 years, because children and youths are active and growing rapidly. On average, boys have slightly higher requirements than girls and this persists throughout adulthood. After the age 18 years energy requirements tend to be lower, but this also depends on the individual's level of activity. By the age of 50 years, energy requirements are even lower, partly due to a reduction in the basal metabolic rate and to a reduced level of activity.

The recommendations given for a daily calorie intake refer to an adult person with moderate activity. For women it should be around 2000 and for men 2500-2800 calories (kcal) each day. Toddlers need about 1300 calories each day. For children aged 7 to 10, the estimated average requirement of energy is 1970 kilocalories a day for boys and 1740 kcal for girls. But this is only a guide; many children will need more than these estimates and some will need less, depending on a number of things, including how physically active they are (Based on: Food Standards Agency - http://www.food.gov.uk).