Pediatric Nutrition in Practice

20 Zemel  Stallings

are increasingly being used to assess bone health
in children with chronic diseases. Other methods
of body composition and bone density measure-
ment are mainly research tools that are not read-
ily applicable to the clinical setting.

Resting Energy Expenditure

Estimating daily energy needs is particularly im-
portant in caring for children with varying pedi-
atric diagnoses that result in undernutrition or
obesity. Their energy needs are difficult to esti-
mate because of variations in metabolic demands
of illness and physical activity as well as the pro-
portion of the body composed of lean tissue. REE
accounts for 60–70% of total daily expenditure
and is used to estimate total energy needs in order
to achieve a specific clinical goal: weight mainte-
nance, loss or gain.
Prediction equations based on age, sex, weight
and length/height have been developed to esti-
mate REE when direct measurement is not pos-
sible. Unfortunately, these equations, derived
from measurements of healthy children, do not
perform well for children with serious health
conditions or altered body composition. The op-
timal approach is to measure REE using an indi-
rect calorimeter or metabolic cart that measures
oxygen consumption and carbon dioxide pro-
duction.
Accurate REE measurement by indirect calo-
rimetry requires standardized conditions such as
early-morning testing after a night of restful
sleep and an 8- to 12-hour (or age- or disease-
appropriate) fast. A 40- to 60-min test enables
initial environmental adjustment and exclusion
of measurements during episodes of movement.
During the test, the patient should be in a quiet,
awake and calm state, be in a supine position and
not have performed any physical activity or re-
ceived any medications known to change heart
rate (such as bronchodilators). Developmentally
normal children who are at least 5 years of age

typically do well while watching a movie. Infants

are evaluated while sleeping. Children with de-

velopmental delay often require sedation with a

short-acting oral agent.

Energy needed for growth or physical activity

or to support therapeutic growth acceleration

must be added to the REE to estimate total energy

requirements. Table 1 shows the dietary reference

intake prediction equations for estimated energy

requirements (kcal/day) and physical activity

factors for healthy infants and children [3]. For

hospitalized or ill children with less spontaneous

physical activity, a factor of 1.3–1.5 × REE is a

better estimate of energy needs. Additional cor-

rections are made for disease severity (such as in

children with cystic fibrosis) or malabsorption.

In patients who require ‘catch-up’ growth, addi-

tional energy may need to be factored into the

energy requirement estimation to achieve the de-

sired rate of growth.

Dual-Energy X-Ray Absorptiometry

DXA is a low-energy X-ray technique (radiation

exposure less than a day’s background exposure)

that measures body composition and regional

bone mass and density. DXA-based bone mineral

content (BMC; g) and density (BMD; g/cm^2 )

measurements are important in clinical care for

identifying children at risk of poor bone accrual

and osteoporosis [4]. Risk factors for pediatric

bone disease include immobility, malabsorption,

inflammation, endocrine disturbances and use of

medications known to affect bone health, such as

chronic glucocorticoid therapy.

BMC or BMD values of the lumbar spine and

total body (excluding the head) should be com-

pared with reference values for healthy children

of the same age and sex and expressed as a z-score

or standard deviation (SD) score. Adjustment for

height is recommended for children with altered

growth [5]. A z-score of 0 is equal to the median

value for the reference population of children of

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 19–22

DOI: 10.1159/000367867