Sleeping metabolic rate in early infancy
Date
2016
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
In the United States, nearly two-thirds of infants receive infant formula by 3
months of age, either in combination with or fully replacing breast milk, the gold
standard for infant nutrition growth. Studies have shown that formula fed infants, the
majority of whom are fed cow’s milk formula (CMF), gain weight more rapidly than
breastfed (BF) infants. Accelerated weight gain in early infancy is of concern as
numerous studies have found an association between rapid infant weight gain and
increased risk for overweight and obesity later in life. Not all infant formulas are
alike in terms of composition and growth outcomes. Infants fed an extensive protein
hydrolysate formula (EHF), which is comprised mainly of free amino acids and small
peptides and has a slightly higher protein content than cow’s milk formula (CMF),
have been found to gain weight similarly to BF infants. The energy balance
mechanisms underlying the differences in weight gain by infant formula type are not
known. However, it is possible that the different protein composition of the infant
formulas (CMF versus EHF) impacts energy expenditure via differences in metabolic
rate. This study had two overarching aims. First, we sought to determine the effect of
formula type (CMF vs. EHF) on sleeping metabolic rate (SMR) in healthy,
exclusively formula-fed infants. Second, we sought to utilize the measures of SMR
to determine which of several available empirical equations for the calculation of
metabolic rate in infants, was most accurate. ☐ A total of 141 mother-infant dyads were recruited from the greater
Philadelphia area. At 0.75 months of age (baseline) when all infants were receiving
CMF and again 3.5-months old, when all infants had been receiving their randomized
formula for nearly three months, SMR was measured via indirect calorimetry. There
were 102 infants with successful SMR at 0.75- months and SMR did not differ
(p=0.148) by eventual formula randomization group. Eighty-three infants had
successful SMR measurements at 3.5 months and formula type did not have a
significant effect (p=0.9633) on SMR. At 0.75 months, we found that the Schofield
weight only performed best for at the individual level at 0.75-months; it had the
highest R2, suggesting good individual level agreement. At 3.5-month, the Schofield
weight only and Oxford weight only equations performed best at the individual level.
Since clinicians aim to calculate energy needs of individual patients, these analyses
suggest the Schofield weight only is most accurate for estimating energy needs of
0.75 and 3.5 month old infants. These results are preliminary and will be repeated
when the data set is complete.