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Table 3 Energy values of macronutrients and specific carbohydrates in
foods (kJ/g) a
cIE DE ME NME
Macronutrients
Fat 39.3 37.4 37.4 36.6
Protein 23.6 21.7 16.8 13.4
Available carbohydrates b
15.7 15.7 15.7 15.7
‘Fibre’/NSP 17.0 7.7 7.7 6.0
Alcohol 29.6 29.6 29.0 25.8
Specific carbohydrates
Available carbohydrates
Glucose monohydrate 14.1 14.1 14.1 14.1
Glucose 15.7 15.7 15.7 15.7
Fructose 15.7 15.7 15.7 15.2
Lactose 16.5 16.5 16.5 16.3
Sucrose 16.5 16.5 16.5 16.3
Starch 17.5 17.5 17.5 17.5
Fibre
Fermentable ‘fibre’ 17.0 11.0 11.0 8.0
Non-fermentable ‘fibre’ 17.0 0.0 0.0 0.0
Resistant starch 17.5 11.4 11.4 8.8
Non-digestible oligosaccharides
General, conventional foods
Isolated/synthetic
17.0 11.1 11.1 8.4
Fructooligosaccharides 17.0 11.1 11.1 8.4
Synthetic polydextrose
(5% glucose)
16.9 6.6 6.6 5.2
Inulin (pure) 17.5 11.4 11.4 8.8
Polyols
Erythritol 17.2 16.6 1.1 0.9
Glycerol 18.0 18.0 18.0 16.6
Isomalt 17.0 11.6 11.2 8.9
Lactitol 17.0 11.1 10.7 8.2
Maltitol 17.0 13.4 13.0 11.5
Mannitol 16.7 12.3 8.1 6.3
Polyglycitol 17.1 13.5 13.2 11.6
Sorbitol 16.7 12.0 11.7 9.7
Xylitol 17.0 14.0 13.7 12.4
Abbreviations: cIE, combustible intake of energy; DE, digestible energy; ME,
metabolizable energy; NME, net metabolizable energy; NSP, non-starch
polysaccharides.
a Based on Livesey (2003a). The values for macronutrients have also been
reported in Livesey (2001), with some trivial differences in the values for
protein and alcohol. For available carbohydrates, see also Livesey and Elia
(1988) and Elia and Livesey (1992). For fibre see text.
b Available carbohydrate (as monosaccharide equivalents) measured by direct
analysis of sugars. When carbohydrate is measured ‘by difference’, the values
increase by 1 kJ/g.
tissues. The overall result is that DE, ME and NME values for
lactose, when there is lactose malabsorption, are lower than
cIE, and lower than the usual values assigned to it, which
assume that all lactose is absorbed from the small bowel
(16.5 kJ/g for cIE, DE and ME values, and 16.3 kJ/g for the
NME). However, this problem is likely to be a minor one,
since individuals with lactose intolerance do not normally
ingest large amounts of lactose because it can produce
undesirable bloating effects and diarrhoea.
European Journal of Clinical Nutrition
Physiological aspects of energy metabolism
M Elia and JH Cummings
The standard DE, ME and NME values obviously
overestimate the actual values in patients with malabsorption
disorders to an extent that depends on the
type of malabsorption disorder and its severity. In contrast,
the standard values may underestimate the actual
values when nutrients are given intravenously and made
directly available to human tissues. This problem is
addressed in detail elsewhere (Livesey and Elia, 1985,
1988). However, the energy value for glucose, which is
usually the dominant energy source for intravenous
nutrition, remains unaltered, but this may not be so for
other types of carbohydrates that may be lost in urine to a
variable extent.
Calculating energy balance
There is interest in estimating energy balance during growth,
development of obesity and undernutrition, as well as
during their treatment. The energy balance can be calculated
from changes in body composition (Fuller et al., 1992;
Heymsfield et al., 2005), which can provide estimates of fat
and protein mass, and in some cases carbohydrate (glycogen
stores are small, but can be measured accurately and
precisely using nuclear magnetic resonance; Taylor et al.,
1992; Casey et al., 2000). Energy balance can also be
calculated from classic balance studies, which involve
measurement of energy intake and energy expenditure. In
calculating energy balance, it is important not to confuse the
energy values of endogenous and exogenous fuels and also
not to confuse different food energy systems (combustible,
ME and NME systems; Table 4).
The ME and NME values of nutrients (kJ/g) that are
mobilized from body stores and used for oxidation during
weight loss are higher than the corresponding food energy
values (Table 4), mainly because digestibility does not apply
to the former but it does to the latter. For example, the ME
values of fat in food is 37.4 kJ/g compared to the value of
39.3 kJ/g of stored fat, and for food protein 16.8 kJ/g
compared to 18.4 kJ/g of tissue protein.
Using body composition techniques, the energy balance
equations is
Energy balance ¼Energy storestime point 2 energy storestime point 1
¼energytime point 2ðcarbohydrate þ fat þ proteinÞ
energytime point 1ðcarbohydrate þ fat þproteinÞ
The energy values for all macronutrients in this equation are
the endogenous food energy values and not the exogenous
food energy values (see Table 4 for combustible energy, ME
and NME values). The body composition approach is usually
only of value in long-term studies where there are large
changes in body composition, which far outweigh measurement
precision. In some such studies, the changes in
glycogen stores are small and therefore they are either be
ignored or estimated. The errors associated with this
approach have been assessed (Elia et al., 2003).