Why we need calories, carbs and company.

Calories aren't bad, because they give us the energy we need to live. Find out what calories really are and learn about their composition and how to calculate caloric requirements.


Calorie is an old unit for measuring energy, i.e. the amount of heat. One kilocalorie is the energy that is needed to heat one litre of water from 14.5 to 15.5 degrees Celsius. Calorie also defines the energy that we take in with our food as well as the energy that our body needs to carry out all its functions.

Calorie or joule?

The international energy unit is really joule (kJ). The energy value of food, however, is given in both units. We generally talk about “calorie”, but the correct term would be “kilocalorie”, in short: kcal.

Kilocalories (kcal) converted into kilojoule (kJ)

1 kcal = 4,184 kJ
1 kJ = 0,239 kcal

Calories and nutrients in our food

The nutrition table provided on the packaging of all food products gives the calories per portion and the nutrients such as carbohydrates (sugar) fat, salt, protein, etc. The Swiss Food Composition Database provides detailed nutritional values.

Kalorien Freund oder Feind Grafik

Example of a nutrition table: Nutritional information for potato crisps.

Calculating the caloric requirements

The nutrition table also shows the calories as a percentage of the daily requirement. This is just a guideline, because caloric requirements are very individual. They not only depend on physical activity, but also on biological factors such as gender, age, size, and genetics. You can calculate how many calories someone would need per day, for example, with the calorie calculator “My caloric requirements” (only German and French) of the Swis Society for Nutrition. Calorie tables and other calorie calculators, for example for calculating the calories needed during sports or the BMI are offered by yazio.com.

Energy suppliers essential to life

Protein, carbohydrates and fat are the main nutrients in our food and they provide our bodies with energy.

Protein is the building material for cell and tissue renewal and serves to transport substances such as vitamins and iron. Recommended daily allowance for adults: 0.8 g protein per kg of body weight, slightly more for sportsmen. A chicken breast weighing 100 g contains around 25 g of protein.

Our brain and red blood cells exclusively obtain energy from carbohydrates and convert around 180 g glucose per day. All excess carbohydrates are stored in the body as fat deposits.

1 g fat has more than twice as many calories (9 kcal) than carbohydrates (4 kcal) and protein (4 kcal). We need fat to protect our organs, to keep us warm and to absorb fat-soluble vitamins. Fat is also an important flavour carrier and helps us to feel satiated. Saturated fatty acids primarily supply the body with energy, but we need very little of these. Polyunsaturated fatty acids, however, are essential: our bodies cannot produce these on their own and we have to take them in through our food (e.g. flaxseed oil).

Small calorie glossary

Different foods deliver a different number of calories per gram. Cheese and nuts, for example, are very energy dense. The same volume of vegetables or fruit contains considerably fewer calories.

We speak of “empty” calories if, aside from energy, a food contains very little in the way of essential nutrients such as vitamins and minerals. Empty calories are found in sweets, baked goods, chips, fast food, fizzy drinks and alcohol.

As good as this may sound, there is no such thing as negative calories. There is nothing we can eat that burns more energy during the eating and digestive process than it adds to the body.

Further information


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