Calories, calorific value and energy needs: What the numbers mean

In short: The calorific value shows how much energy a food provides (kcal or kJ); daily needs depend on age, height, activity and body and can only be estimated roughly.

In more detail: Energy is neither a “good” nor a “bad” quantity: the body needs it. What matters is the ratio between intake and expenditure and the quality of food. This is general information and does not replace medical advice. With complaints, illnesses, pregnancy or medication, ask a doctor or pharmacist.

In Depth

Units and nutrients

kcal (kilocalories) and kJ (kilojoules): 1 kcal ≈ 4.184 kJ. On packaging the calorific value is given per 100 g/ml (and partly per portion). Per gram provide:

• Fat: 9 kcal
• Alcohol: 7 kcal
• Carbohydrates: 4 kcal
• Protein: 4 kcal
• Fibre: about 2 kcal Energy density (kcal per 100 g) is high for oil, nuts, sweets and low for vegetables, fruit and soups.

How much is needed?

The basal metabolic rate is the energy the body uses at rest (roughly 1,200 to 2,000 kcal/day depending on the body). Add exercise and daily life (activity expenditure). The total need of adolescents and adults is often between about 1,800 and 3,000 kcal a day, active teenagers and athletes more. Formulas and calculators give only estimates; individual differences are large. Growing adolescents need sufficient energy and nutrients; diets are problematic at this age.

Counting calories: benefits and limits

Counting can create awareness of amounts, but figures are imprecise (packaging data may deviate, cooking changes things), and composition (fibre, protein, processing) influences satiety and health. Constant counting can lead to disordered eating. More important are meal rhythm, vegetables, wholegrain, protein, few sugary drinks and exercise.

Help with eating problems

Whoever is strongly preoccupied with weight and calories, skips meals, fears eating or experiences binge eating should seek help early (family doctor, counselling centres, helplines for eating disorders). These are serious, treatable illnesses. Comparisons with images from social media distort body image.

See also: Reading the nutrition table, Nutri-Score, Trans fats and saturated fats, Hidden sugar