Calories. We count them. We curse them.
Ask the average person to define ‘calorie’ and you’ll usually hear something like, “They’re things in food that if you eat too much of them, you’ll get fat.” Even though we think of them this way, calories aren’t really ‘things’ in food. You can’t see them, touch them, pick them out or push them to the side of your plate. Calories are actually a measure of the energy in your food, and no matter what activity your body is performing—whether it’s pumping blood or pumping iron—it needs energy in the form of calories to make it happen.
You probably think of your food as fuel—and it is. But the energy that your body needs – in the form of calories—is locked within the proteins, fats and carbohydrates that make up the food that you eat.
It’s not until you fully process that food that the energy is released and can be used to power activity within each and every cell of your body. A calorie is simply a way of expressing the amount of energy that can be released from the foods that you eat.
Putting food into your body is not unlike what happens when you put gasoline in your car. Simply having gas in the tank isn’t going to make the car move forward. The fuel has to go to the engine and ignite, which releases energy that allows the car to move. In much the same way, your digestive system acts as your body’s engine. It processes the fuel and releases energy from your food—and your body then uses that energy to perform virtually every function it undertakes.
The amount of energy (calories) in a given food depends on how much protein, fat and carbohydrate it has. Every gram of protein or carbohydrate in a food provides 4 calories of energy to the body. But fats pack more than twice as much—9 calories per gram—which is why fatty foods are often called ‘energy dense.’
When you think of calories as energy, it’s a bit easier to understand how calorie balance affects your body weight. If the energy available to your body (from the foods that you eat) is matched with the energy your body uses to carry out all its functions, then your weight should stay stable. But if there’s more food energy available then your body can use, you’ll stash it in your ‘reserve tanks’—those fatty deposits on your hips, belly and thighs.