Calorie
The calorie is the unit used to measure the energy in food – packaging usually says kcal, short for kilocalorie.
Ausführlich erklärt
A calorie is a unit of energy – it tells you how much fuel a food provides for your body. Strictly speaking, one calorie heats one gram of water by one degree Celsius. Because that's tiny, food energy is measured in kilocalories (kcal): 1 kcal = 1,000 calories. When someone talks about “300 calories”, they almost always mean 300 kcal.
In the EU, packaging shows kilojoules (kJ) alongside kcal – the official unit under the EU Food Information Regulation. The conversion: 1 kcal is roughly 4.2 kJ. Both figures describe the same amount of energy – so you only need to keep an eye on one of them.
Where does the energy come from? From the three macronutrients: one gram of carbohydrate provides 4 kcal, one gram of protein also 4 kcal, and one gram of fat 9 kcal. Alcohol weighs in at 7 kcal per gram, fibre at around 2 kcal. Water, vitamins and minerals contain no calories.
Your body uses energy around the clock – for your heartbeat, breathing, thinking and movement. This requirement is called total daily energy expenditure. If you eat more than you use over a long period, your body stores the surplus as fat; if you eat a little less, it draws on these reserves. As a rough rule of thumb, a kilogram of body fat contains about 7,000 kcal – although energy use also drops slightly as your weight goes down.
Important for families: calories aren't the enemy, they're fuel. Children need enough energy for growing and running around – for them, what counts is the quality of the food, not counting. Adults who want to lose weight can glance at the calories to get a feel for portion sizes without weighing every bite.