Energy needs from gestation and birth to older age

Before birth: two connected systems

The FAO/WHO/UNU report estimates additional maternal energy costs of about 85, 285 and 475 kcal/day across the three trimesters under its assumptions. These increments are not fetal kcal/kg requirements. Dividing them by fetal weight would mix maternal tissue change, maternal metabolism and fetal development. [1]

Birth and infancy

For combined feeding groups, FAO infant reference estimates are about 110 kcal/kg/day at month 1, 81 at month 6 and 80 at month 12, including growth. They are population estimates, not instructions to restrict milk intake. [2]

For healthy growing preterm infants, ESPGHAN distinguishes resting expenditure of approximately 60–70 kcal/kg/day from total enteral intake of 115–140 kcal/kg/day. Prematurity and feeding route prevent direct comparison with adult intake. [3]

Childhood, adolescence and adulthood

FAO reference values for boys/girls are 82.4/80.1 kcal/kg/day at 1–2 years, 74.5/71.5 at 5–6, 64.6/57.8 at 10–11 and 50.3/44.1 at 17–18. Growth and the reference activity assumptions matter; these are not age-specific minimums. [4]

Pontzer and colleagues found distinct developmental phases in body-composition-adjusted expenditure, with adult stability roughly between 20 and 60 before later decline. An adjusted statistical result is not a constant raw kcal/kg ratio. [5]

Body composition does not explain everything

Hsu and colleagues compared organ measurements and resting expenditure in children and young adults. Brain and liver mass improved their model but did not eliminate the contribution of age [7]. Developmental comparisons should account for both tissue proportions and possible differences in tissue metabolic rates. These resting measurements are distinct from the dietary requirement estimates above.

Older age and a testable comparison

ESPEN uses 30 kcal/kg body mass/day as an individually adjusted guide for older people. [6] EPK–010 brings these figures together while retaining their original populations and denominators. A useful analysis would compare like measurements within age groups before examining differences between groups. It would measure strength and mobility alongside energy intake, rather than assume low expenditure proves underfeeding.

Related working papers

Read the relevant PDFs: EPK–001 to 007 are the revised version 1.2 papers; EPK–008 to 010 are version 1.0 supplements. Earlier PDFs and DOI records remain on the paper archive.