Are formulas such as Harris-Benedict reliable?

These are estimates of basal metabolism, to be multiplied by an activity level. In its 2016 work, ANSES considered that none of the five equations usable in adults (including Harris-Benedict and Mifflin) is preferable to the others. They provide an approximate figure, which may differ from your actual expenditure.

Do requirements increase during pregnancy?

Yes. EFSA adds to the requirement of a non-pregnant woman approximately 70 kcal per day in the first trimester, 260 kcal in the second and 500 kcal in the third, as well as approximately 500 kcal per day during the first six months of breastfeeding. For personalised monitoring, consult your doctor or midwife.

How many calories per day? Official guidelines

What is energy requirement?

Energy requirement is the amount of energy the body needs each day to function. It is expressed inkilocalories (kcal), or in kilojoules (kJ): 1 kcal is approximately equal to 4.19 kJ. In everyday language, people simply say "calories".

According to ANSES, a person's total energy expenditure, and therefore their requirement, depends on three components:

Basal metabolism: the energy expended at rest to keep the body alive (breathing, circulation, temperature regulation, etc.).
Thermogenesis: the energy expended to digest and utilise food.
Postural and physical activity: standing, walking, working, exercising. This is the most variable component, and therefore the most adjustable.

The ratio between total expenditure and basal metabolism is called thephysical activity level (PAL). In the French population, ANSES indicates that physical activity accounts for an average of 35 to 40% of total energy expenditure, which corresponds to a moderate PAL of approximately 1.65 times basal metabolism.

Official reference values for an adult

There is no single figure. EFSA (2013) calculatedaverage requirementsby multiplying basal metabolism by four activity levels: 1.4 (inactive, sedentary), 1.6 (moderately active), 1.8 (active) and 2.0 (very active). The calculation assumes a weight corresponding to a BMI of 22. Here are the values for ages 18-29, converted to kcal (rounded; the conversion is ours):

Inactive (1.4): 9.8 MJ, i.e. approximately 2,340 kcal for a man, 7.9 MJ, i.e. approximately 1,890 kcal for a woman
Moderately active (1.6): 11.2 MJ, i.e. approximately 2,680 kcal for a man, 9.0 MJ, i.e. approximately 2,150 kcal for a woman
Active (1.8): 12.6 MJ, i.e. approximately 3,010 kcal for a man, 10.1 MJ, i.e. approximately 2,410 kcal for a woman
Very active (2.0): 14.0 MJ, i.e. approximately 3,340 kcal for a man, 11.2 MJ, i.e. approximately 2,680 kcal for a woman

The same table shows that requirements decrease with age. At a moderate activity level (1.6), they fall for example from 11.2 to 10.8 MJ (approximately 2,580 kcal) in men aged 30-39, then to 9.6 MJ (approximately 2,290 kcal) at 60-69 years. In women, from 9.0 to 8.7 MJ (approximately 2,080 kcal), then to 7.8 MJ (approximately 1,860 kcal).

ANSES, in its 2016 work to update PNNS guidelines, carried out a similar exercise using INCA2 survey body sizes, a BMI of 22 and a median activity level of 1.63. The result: a requirement of approximately2,600 kcal per day for men aged 18 to 69 and 2,100 kcal for women aged 18 to 59(averages across several formulas). These are orders of magnitude, not individual recommendations.

Common estimation formulas

To estimate basal metabolic rate, prediction equations are used that take into account sex, age, weight and height. The best known are those ofHarris and Benedict (1919)and ofMifflin and colleagues (1990), whose formula is known as Mifflin-St Jeor. The result is then multiplied by an activity coefficient, such as NAP.

These formulas remain approximations. In its report, ANSES, supported by EFSA, considered that none of the five equations usable in adults (including these two, as well as those of Schofield, Müller and Henry) is preferable to the others, and it used the average. Depending on the equation chosen, the difference between formulas reaches, for example, approximately 250 kcal per day for men aged 50-59 in its tables.

What influences energy requirements

Age: requirements decrease from the age of thirty, as shown in EFSA tables.
Sex: at equal age and activity levels, reference values are higher for men.
Height and weight: a larger body expends more energy at rest.
Physical activity: at equal weight, the requirement of a very sedentary person is significantly lower than that of an active person. For sport, seeNutrition for athletes.
Pregnancy and breastfeeding: EFSA adds 0.29 MJ per day in the first trimester (approximately 70 kcal), 1.1 MJ in the second (approximately 260 kcal) and 2.1 MJ in the third (approximately 500 kcal). For a woman who breastfeeds during the first six months, the supplement is 2.1 MJ (approximately 500 kcal).

Forchildren and adolescents, requirements depend strongly on age and growth. EFSA publishes values by age and sex in the same summary table, starting from 7 months. It is better to refer to these, or to seek a paediatrician's advice, than to apply adult guidelines. For special situations, a healthcare professional is the appropriate person to consult.

How energy is distributed between proteins, fats and carbohydrates

Calories come from three families of nutrients. In European labelling, the conversion factors are4 kcal per gramfor carbohydrates and proteins,9 kcal per gramfor fats, 7 kcal for alcohol and 2 kcal for fibre.

For a healthy adult, ANSES (2016) recommends the following ranges, expressed as a proportion of total energy intake:

Proteins: 10 to 20%
Fats: 35 to 40%
Carbohydrates: 40 to 55%

Children, the elderly and highly active individuals have specific guidelines. EFSA, for its part, adopts ranges of 20 to 35% of energy for fats and 45 to 60% for carbohydrates in adults. The quantities in grams are detailed inHow much protein per day?andSugar, salt, fats, carbohydrates and fibre: daily guidelines.

Reading calories on a label

EU Regulation on consumer information (Regulation No 1169/2011) stipulates that the mandatory nutrition declaration must begin with theenergy value, followed by fats, saturated fatty acids, carbohydrates, sugars, proteins and salt. It is expressedper 100 g or per 100 ml, which allows comparison between two products. It may also be indicatedper portionor per consumption unit, provided that the portion size is mentioned nearby and the number of portions per package is specified.

The label displays energy in kJ and kcal. The reference intake for a typical adult, used to calculate percentage reference intakes, is2,000 kcal (8,400 kJ). This is a labelling guideline, not your personal requirement.

Pitfalls: liquid calories and portions

Beverages: a glass of soda, juice or smoothie does not satisfy hunger like a meal, and it is easy to drink them without thinking. The ANSES expert committee (2016) considers that sugars, particularly in liquid form (sodas, nectars, fruit juices, smoothies), contribute to weight gain, with a level of evidence described as "convincing".
Portions: values per 100 g do not reflect what you actually eat. A package may contain several portions: multiply by the amount actually consumed.

On Yumiq, the product sheet indicates the number of additives detected (harmless, to monitor or at risk), and the Yumiq-Score penalises additives flagged by EFSA (risk of overexposure) or ANSES in the Open Food Facts taxonomy: a way to look beyond calories alone.

Estimating your own value

To obtain a personal estimate, you can use Yumiq's "Daily Calorie Calculator" page, which applies this type of estimation. It is an approximation. If you wish to change your diet,Dietary rebalancing: where to start?proposes a gradual approach. For a restrictive diet or a medical condition, consult a doctor or dietitian.

Key takeaways

Official estimates for a healthy adult: approximately 2,600 kcal (men) and 2,100 kcal (women) according to ANSES; EFSA provides details by age and activity level.
Estimation formulas provide an approximation, not an exact value.
ANSES guidelines: 10 to 20% protein, 35 to 40% fat, 40 to 55% carbohydrates.
On the label, compare products per 100 g, then calculate what you actually eat, including beverages.
Pregnancy, children, illness, weight goals: seek advice from a healthcare professional.

How many calories per day?