What is a calorie? And why is this term important when we're talking about weight? A calories is the amount or measurement of heat necessary to raise the temperature of one gram of water one degree on the Celsius scale.
Excuse me? What does this have to do with why my pants won't fit?
A calorie is also the unit of measurement of energy produced by food when it is oxidized, or used, in the body. Calories are like fuel for our bodies. We need them for our bodies to run. But if we pump more fuel into our bodies than we need for the amount of activity we do, the excess fuel just sits there. Your body will store this excess, unused fuel. It may store it as muscle, if you perform enough physical, muscle-building exercises such as weightlifting, or it may store it as fat.
You need to maintain a balance between the amount of calories you take in (food) and the amount of calories you use (exercise). You "burn" your body's fuel - calories - when you perform physical activities, and you also burn calories just by sitting still, breathing and living each day.
If you perform enough physical activity, you may increase the amount of calories (or energy units) you burn each day and raise the amount of calories (or energy units) you need each day. So a person who is physically active can eat more calories each day without gaining weight, because this person uses the fuel he or she pumps in, instead of storing it as fat.
Each person is different when it comes to the amount of calories he or she needs each day. The amount of calories a person needs for fuel varies according to age, height, gender, amount of physical activity and other factors.
