We all need energy to grow, stay alive, keep warm and be active. Energy is provided by the carbohydrate, protein and fat in the food and drinks we consume. It is also provided by alcohol. Different food and drinks provide different amounts of energy.
The amount of energy (measured in units of calories or kilojoules) a food contains per gram is known as its energy density.
- Foods with fewer calories per gram such as fruits, vegetables, soups, lean protein- and carbohydrate-rich foods have a relatively low energy density.
- Foods with a high fat and/or low water content such as chocolate, fried snacks, nuts and crackers have a relatively higher energy density.
Having a diet with a low energy density overall can help to control calorie intake while helping to avoid feeling too hungry.
Carbohydrate is the most important source of energy for the body because it is the main fuel for both your muscles and brain. Sources of carbohydrate include starchy foods, e.g. bread, rice, potatoes, pasta, pulses and breakfast cereals.
Different people need different amounts of energy. This depends on your basal metabolic rate (BMR), which measures the amount of energy you use to maintain the basic functions of the body, as well as your level of activity.
Some activities use more energy than the others. The more active you are, the more energy your body uses up. Being physically active can increase your muscle mass and this means you will actually be using more energy all the time, even when you are resting.
Your weight depends on the balance between how much energy you consume from food and drinks, and how much energy you use up by being active. When you eat or drink more energy than you use up, you put on weight; if you consume less energy from your diet than you expend, you lose weight; but if you eat and drink the same amount of energy as you use up, you are in energy balance and your weight remains the same.
In the UK, the majority of adults are either overweight or obese, which means that many of us are consuming more energy than we need from food and drinks and need to try to reduce our energy intake in order to move towards a healthy weight.