Understanding calories

The amount of energy in an item of food or drink is measured in calories.

When we eat and drink more calories than we use up, our bodies store the excess as body fat. If this continues over time we may put on weight.

As a guide, an average man needs around 2,500kcal (10,500kJ) a day to maintain a healthy body weight.

For an average woman, that figure is around 2,000kcal (8,400kJ) a day.

These values can vary depending on age, size and levels of physical activity, among other factors.

You can check whether you're a healthy weight by using our BMI healthy weight calculator.

Calories and energy balance

Our bodies need energy to keep us alive and our organs functioning normally. When we eat and drink, we put energy into our bodies.

Our bodies use up that energy through everyday movement, which includes everything from breathing to running.

To maintain a stable weight, the energy we put into our bodies must be the same as the energy we use by normal bodily functions and physical activity.

An important part of a healthy diet is balancing the energy you put into your bodies with the energy you use.

For example, the more physical activity we do the more energy we use.

If you consume too much energy on one day, don't worry; just try to take in less energy on the following days. 

Burning calories

The amount of calories people use by doing a certain physical activity varies, depending on a range of factors, including size and age.

The more vigorously you do an activity, the more calories you will use. For example, fast walking will burn more calories than walking at a moderate pace.

Find out how the body burns calories in How can I speed up my metabolism?
If you're gaining weight, it could mean you've been regularly eating and drinking more calories than you've been using.

To lose weight, you need to use more energy than you consume, and continue this over a period of time.

The best approach is to combine diet changes with increased physical activity. Find out more about how much physical activity you should be doing.