Calories
All food supplies you with calories, the ‘fuel’ your body burns to produce energy and keep you alive.
The word calorie is actually a scientific term to describe the level of heat energy in any given amount of food. You’ll see this expressed on food packaging as kilojoules (kj) or kilocalories (kcal). For simplicity’s sake, this is generally shortened to the more familiar ‘calories’.
If you want to convert a calorie to a joule for any reason, however, it’s simple: one calorie is 4.2kj.
Each kind of nutrient provides a different amount of energy for its weight. That’s why some foods are higher in calories, and therefore more fattening, than others.
For instance:
- 1g carbohydrate supplies 4 kcal (17kj).
- 1g fat supplies 9 kcal (38kj).
- 1g protein supplies 4 kcal (17kj).
- 1g alcohol supplies 7 kcal (29kj).
You can see from the figures above that the calorie content of a food depends on what proportions of fat, carbohydrate and protein it contains. A high fat food is higher in calories than a carbohydrate rich one, for instance.
Calories and exercise
When food is digested, fat, protein and carbohydrate are released, broken down and then absorbed into the bloodstream. This then gets released into trillions of body cells where it’s used to keep your body alive, help carry out all your various bodily processes and fuel your muscles for sport and exercise. Energy from any food that you don’t need immediately is stored up as body fat, or glycogen, to be used later.
It’s a simple equation; burn more calories than you eat and you end up with less fat. Burn fewer calories than you eat and they get converted to fat and stored up for later. And you get larger!
Because exercise increases the amount of energy you use, it will increase the number of calories you burn. When those calories are all used up, your body will then start to use your reserves of fat, turning it into energy and helping you lose weight.
Even better than that, raising your metabolic rate (the speed at which your body consumes energy) by exercising means you increase the amount of calories your body needs to function for the rest of the day.
That’s why how active you choose to be is every bit as important in losing weight as what you choose to eat.