What are calories?
Calories (kcal) are the units used to measure the amount of energy in foods and drinks.
Our bodies need energy to function - everything we do, from breathing to being active, requires energy.
We get energy from the foods and drinks we consume. But if we eat and drink more energy than we need, our bodies tend to store the extra energy as fat.
This is important because, after choosing not to smoke, staying in shape is the most important way we can reduce our risk of cancer.
Being a healthy shape and weight can also help to reduce the risk of other diseases like heart disease and Type 2 diabetes.
How many calories do we need?
On average, women need roughly 2,000 calories a day and men need roughly 2,500.
Younger people and people who are very physically active may need more calories, and people who are older or less physically active may need less.