A calorie is a unit used to measure energy.
In terms of weight management it usually refers to either the energy we take in from food and drink or the energy we use up through keeping our body working or being physically active.
All weight loss programmes aim to shift the energy balance so that the energy going in is less than the energy going out. We can do this by:
However, doing both at the same time is the best way to lose weight and keep it off for good.