Understanding calories

The amount of energy in food or drink is measured in calories. When we eat and drink more than we use up, our bodies store the excess as body fat.

A man needs around 2,500 kcals a day to maintain a healthy body weight and a woman around 2,000 kcals. These values can vary depending on age, size and levels of physical activity.

Our bodies need energy to keep us alive and keep our organs functioning normally. The body uses that energy through everyday movements from breathing to running. For a stable weight, the energy we put into our bodies must be the same as the energy we use through normal bodily functions and physical activity.

Knowing the calorie content of food and drink can help ensure you’re not consuming too much. The calorie content of many foods is stated on the packaging as part of the nutrition label. A “kilocalorie” is another word for what is commonly called a “calorie”, so 1,000 calories will be written as 1,000 kcals.

The label will usually tell you how many calories are contained in 100 grams or 100 millilitres of the food or drink, so you can compare the calorie content of different products.

Many labels will also state the number of calories in “one portion” of the food.

But remember that the manufacturer’s idea of “one portion” may not be the same as yours, so there could be more calories in the portion you serve for yourself.