New Reference Values for Energy Intake Open Access

The D-A-CH ‘reference values for nutrient intake' [1] are jointly issued by the nutrition societies of Germany, Austria and Switzerland (the abbreviation D-A-CH arises from the initial letters of the common country identification for the countries Germany (D), Austria (A) and Switzerland (CH)). Currently, the ‘reference values for nutrient intake' are being revised. Following vitamin D [2], calcium [3] and folate [4] the revised reference values for energy were published in February 2015.

For the determination of energy expenditure either the method with doubly labelled water (DLW) or the factorial method can be used. Using the DLW method it is possible to determine energy expenditure under everyday conditions. On the basis of the energy expenditure determined using this method (total energy expenditure (TEE), including energy expenditure for tissue synthesis during growth but not energy storage in developing tissue), regression equations are produced dependent on anthropometric variables [5]. The proportion of energy expended via physical activity cannot be shown separately using this method. However, since the reference values for energy intake for children, adolescents and adults are to be shown depending on physical activity, the predictive equations for calculating energy expenditure based on the DLW method are not used for these age groups. For infants, the reference values for energy intake are calculated on the basis of the prediction equations developed using the DLW method.

When using the factorial method, resting energy expenditure (REE) is multiplied by the physical activity level (PAL) in order to calculate energy expenditure. Here, REE for adults is calculated with the help of various equations based on a database on REE in Germany [6]. This contains data on body composition and REE on the basis of a random sample (n = 2,528) of healthy people aged between 5 and 91. The data were collected between 1985 and 2002 in Germany in various centres using a standardised and comparable method. Since the equations developed by Henry [7] are based on the largest available database for children and adolescents, they are used here for the purpose of calculating REE.

The PAL values within a population may vary greatly and may deviate from the desirable PAL values. Therefore, reference values that are based on desirable PAL values tend to suggest inappropriately high energy intake. Consequently, no mean PAL value for the general population or individual age groups established by means of studies is stated, but the energy expenditure for specific PAL values is presented [8,9].

The aim of reference values for energy intake is achieving an energy balance or an energy intake by means of which a body weight will be achieved, which in turn promotes health in the long term. Major differences in physical activity and in the anthropometric parameters lead to a very large coefficient of variation regarding energy requirement within the population. The reference values for energy intake are therefore stated as guiding values in terms of aids for orientation. They are not readily applicable to individual persons. Whether an individual's energy intake corresponds to energy expenditure or not can be roughly assessed through regular weight checks.

The additional energy expenditure for growth, pregnancy and lactation is calculated using data from well-nourished infants and children and women with a normal course of pregnancy and lactation.

The determination of the energy expenditure for infants is based on data obtained using the DLW method on full-term births and well-nourished infants [10] (online suppl. fig. S1; for all online suppl. material, see www.karger.com/doi/10.1159/000430959). The median body weight of infants that is needed to calculate energy expenditure is determined using the WHO child growth standards [11] (online suppl. table S1).

The determination of energy expenditure using the DLW method includes energy expenditure for tissue synthesis but not energy storage in growing tissue. Consequently, this has to be considered additionally when deriving the reference values for infants. Energy storage in developing tissue can be calculated using estimates from a multi-component model as well as an energy content of 5.65 kcal or 23.6 kJ per every 1 g of stored protein and of 9.25 kcal or 38.7 kJ per every 1 g of stored fat [12,13] (online suppl. table S2).

The guiding values for energy intake for infants that result in accordance with this approach are shown in table 1 (online suppl. table S3 for MJ/day and detailed calculation). The calculation of energy intake by means of energy intake via breast milk reveals comparable results.

As in infants, the energy expenditure for growth in children and adolescents is comprised of energy expenditure for tissue synthesis and energy storage in developing tissue. Energy expenditure for tissue synthesis is part of the calculation of energy expenditure using the equations developed by Henry as described earlier [7]. Energy storage in developing tissue still has to be added in order to determine TEE in children and adolescents. Energy expenditure for growth in this age group accounts for approximately 1% of TEE [12]. In line with the FAO/WHO/UNU approach [12], energy storage in developing tissue is taken into account by taking a coefficient of 1.01 as a basis when calculating TEE (REE × PAL × 1.01). Table 2 shows the guiding values for energy intake in kcal/day for children and adolescents for PAL 1.4, 1.6 and 1.8 (online suppl. table S4 for MJ/day and PAL-value 2.0).

The basis for the derivation of guiding values for energy intake for adults is an energy balance in a reference person of a certain height and weight corresponding to a BMI of 22 kg/m² (online suppl. table S1). The guiding values were calculated using a regression equation produced on the basis of data regarding REE from the database on REE in Germany [6] (online suppl. fig. S2). By means of multiplication with the PAL values, the guiding values for energy intake can be derived. Table 2 shows both the REE and the guiding values for adults for PAL values of 1.4 to 1.8 in kcal/day (online suppl. table S5 for MJ/day and PAL-value 2.0).

With regard to energy expenditure, men and women aged above 65 represent a particularly heterogeneous group. This applies both to REE as well as to energy expenditure for physical activity. REE varies due to different physical composition, which in turn is dependent on age and activity levels. Here, with regard to physical activity, we find people on the one hand with PALs comparable to those of younger persons and on the other hand, this group also includes those people who are clearly impaired with regard to mobility and activity [14]. In individual cases, energy expenditure can therefore deviate greatly from the guiding value.

Body weight gain during pregnancy represents the main determinant for additional energy expenditure during pregnancy. In agreement with the WHO [15] and the European Food Safety Authority (EFSA) [8] a gain in body weight of approximately 12 kg is used here for the derivation of reference values for the energy intake for pregnant women (given a pre-pregnancy BMI of 18.5-24.9 kg/m²), which is associated with optimum health of mother and fetus [15]. According to the FAO [12,] this corresponds to an increase in protein mass of 597 g and in fat mass of 3.7 kg for the whole pregnancy (online suppl. table S6).

The storage of energy in developing tissue is not distributed evenly throughout the entire pregnancy. Protein storage takes place in the second (20%) and third (80%) trimesters. Assuming that the percentage of fat storage follows the same pattern as the increase in body weight, 11, 47 and 42% of the fat is deposited in the first, second and third trimesters respectively [10,16] (online suppl. table S6).

Using DLW data sets and assuming a gain in body weight during the pregnancy of 12 kg, the FAO [12] derives an increase in energy expenditure totalling 38,560 kcal. This is distributed across the first, second and third trimesters as 20, 85 and 310 kcal/day, respectively. By adding the energy expenditure for energy storage in developing tissue during pregnancy it is possible to establish the additional energy expenditure in the pregnancy. Additional energy expenditure for the pregnancy amounts to 76,530 kcal and is distributed across the first, second and third trimesters (online suppl. table S6). The additional energy intake of 70 kcal/day for the first trimester calculated in this way is negligible and to be disregarded. As guiding values for additional energy intake for pregnant women +250 kcal/day for the second trimester and +500 kcal/day for the third trimester are stated. The guiding values for additional energy intake are valid only given normal weight prior to the pregnancy, a desirable weight development during the pregnancy (weight gain of 12 kg by the end of the pregnancy), as well as undiminished physical activity. For overweight women and in cases of reduced physical activity during pregnancy, the additional energy requirement is less, which means that the amount of additional energy intake needs to be adapted in order to prevent undesired weight gain.

Energy expenditure during lactation is increased depending on the intensity and duration of breastfeeding. In agreement with other professional bodies [8,12,17] the guiding values for energy intake during lactation were determined using the factorial method. Accordingly, it is possible to calculate energy expenditure in the lactation period using the quantity of milk produced, the energy content of the breast milk and the energetic efficiency for the milk production.

An exclusively breastfed infant will receive approximately 500 kcal/day [18,19] via the breast milk in the first 4-6 months given a liquid intake of 750 ml [20]. Taking the energetic efficiency for milk production of approximately 80% into account (according to [21] from [12,22]), energy expenditure amounts to 656 kcal/day.

During the lactation period, in the first 6 months after birth, 170 kcal/day may be released from the fat reserves accumulated during the pregnancy (this corresponds to a loss in body weight of 0.8 kg/month) (according to [21] from [12,22]) and may contribute toward meeting the increased energy expenditure during the lactation period. Consequently, for exclusive breastfeeding during the first 4-6 months, the guiding value for additional energy intake is 500 kcal/day.

Upon introducing complementary feeding (from the start of the 5th month or at the latest the start of the 7th month), it is possible to continue partial breastfeeding. The average amount of milk produced then falls to around 600 ml/day [20]. Taking the energetic efficiency for milk production of approximately 80% into account, energy expenditure amounts to 525 kcal/day. This approximately corresponds to the additional energy expenditure for exclusive breastfeeding for 4-6 months. However, since energy expenditure is dependent on the intensity and duration of the breastfeeding, no guiding value for additional energy intake is specified for partial breastfeeding after 4-6 months in agreement with other professional bodies [8,12,17].

An adequate supply of energy is ensured by means of a level of energy intake which over a long period of time is associated with a body weight that promotes health.

The energy density of food is an important factor influencing weight gain as well as successful weight loss and weight maintenance and therefore is of major significance, given the backdrop of high prevalence of overweight within the population. Current scientific data indicates a positive association between the energy density of food consumed and body weight. When viewed in conjunction with nutrient density, energy density is a useful concept for assessing food other than drinks [23].

In realising an energy balance, which over a long period of time is associated with a body weight that promotes health, it is important not only to have an adequate level of energy intake via a balanced wholesome diet but also an appropriate level of energy expenditure through exercise and sport. It is recommended to engage in moderate physically activity for at least 30-60 min per day [24,25,26].