All About Calories
A calorie is what we consume each time we drink or eat. We need these units of energy to help us go about our daily tasks, breathing, moving, thinking etc. What we need to establish is how many calories we need per day without doing any other activities other than the basic functioning. We can then amend our consumption based on what our bodies require.
When we overeat we are simply taking on too many calories that our bodies cannot burn off again and therefore begin to store the extra as fat which will over time result in weight gain.
This is a direct result of taking on board too many calories for our system, they therefore do not get used up and are stored as fat.
Our system can either burn calories or store them. Hence we work out because it makes us feel good (releasing endorphins) and it stokes the system to go into burn mode. When we work, undertake activities and our body fulfills its function we are burning fuel. There are many factors that can affect the effective thermodynamics but the basic rule of thum is to consume the amount of calories our body can burn each day.