What is a calorie in food – a unit of energy applied to both food and drink we take in. One calorie measures the amount of heat needed to raise the temperature of 1 kilogram (2.2lbs) of water by 1°C (1.8°F). Boiling a pot of water might use 100 calories on a cold day.
Calories in food and drink measure the amount of potential energy in that food. They are not the only thing our body needs. If our food is poor quality, we can find ourselves consuming a lot more calories to get a small amount of nutrition.
Different types of food have different amounts of calories for the same weight.
- 100 grams of carbohydrate has 400 calories.
- 100 grams of protein has 400 calories.
- 100 grams of fat has 900 calories
We use up this potential energy by metabolizing it. First, we break down the food into molecules.
- carbohydrates into glucose and other sugars
- fats into glycerol and fatty acids
- proteins into amino acids
Next, parts of our body use these molecules for building, repairs and fuel. We need different amounts of calories depending on our metabolic rate and the body weight we have to maintain. Someone with a high metabolic rate needs more calories than someone with a low metabolism does. It takes more energy to heat 20lbs of water in our pot than 10lbs.
What are they for?
We use a certain number of calories to keep our heart and other organs and processes functioning. We also need a certain amount to maintain our body temperature. We call the number of calories needed to maintain us our basal metabolic rate.
For physical activity
All activities use calories, even sleeping (about 77 per hour depending on body weight). Just moving around, walking, talking and thinking uses a certain number of calories.
To burn up a certain number of calories to boil our kettle is a lot of work if we’re trying to do it consciously. To actually burn that 500 calorie piece of chocolate cake requires mammoth effort if you think about it like this. For instance, if you are 130lbs, you need about 1 hr of high impact aerobics to burn 400 calories.
To digest calories
The food we eat needs a certain amount of energy to break down and digest. To put it another way we lose about 10% of foods energy in digestion.
What is a Calorie Excess?
If we take in more calories than we use up for maintaining our body and in physical activity, we will put on weight. If we take less in, we will lose weight.
The tricky part is that bodies adjust in the short term to the amount we intake and expend, by lowering or raising the rate of burning or metabolism and easing up on non-essential functions. It’s like having a certain amount of money to last the week. By the end of the week, you become very choosy about what you spend