The purpose of this research study is to understand how infants metabolize different meals and to develop clinical tools which identify infants as having two different phenotypes. The phenotypes are the 1) metabolic "thriftiness" and 2) the metabolic flexibility.
Aged 2 weeks to less than 17 weeks at screening
Being fed human milk as a primary source of food
Be willing to consume one meal of infant formula
Be willing to complete a DXA measurement
Unable to complete the screening visit and two clinic visits within 14 days
Born with health conditions that would render procedures unsafe
Born earlier than 35 days and 0 weeks gestation
Eating supplemental foods
Up to 40 infants who are less than 17 weeks will be recruited to participate in this study.
Other
Prospective
Meal Test - Human Milk
Other interventionInfants will be fed a mixed meal test (meal challenge test) of human milk from his/her human milk donor (e.g., mother). Since all infants enrolled in the study consume human milk as a primary food source, this meal challenge test represents their standard meal, at a larger size. The meal test is provided inside a metabolic chamber to measure energy expenditure (VCO2 and VO2) before and after the meal. The amount of human milk that the infant is fed is estimated using the age and sex specific equations from the 2023 DRI for infants aged 0-2 years. Infants will be provided 20% of their predicted energy needs, which is equivalent to between 4-6 ounces of food for most infants of this age. The caloric content for human milk is be estimated at 20 kcals/ounce.
Meal Test - Infant Formula
Other interventionInfants will be fed a mixed meal test (meal challenge test) of ready-to-feed infant formula. Since all infants enrolled in the study consume human milk as a primary food source, this meal challenge test represents a meal different from their habitual food intake and is a standard meal that all participants receive. The meal test is provided inside a metabolic chamber to measure energy expenditure (VCO2 and VO2) before and after the meal. The amount of infant formula that the infant is fed is estimated using the age and sex specific equations from the 2023 DRI for infants aged 0-2 years. Infants will be provided 20% of their predicted energy needs, which is equivalent to between 4-6 ounces of food for most infants of this age. The caloric content for the ready-to-feed infant formula is 20 kcals/ounce.
Energy expenditure difference from baseline to postprandial
Percent difference from baseline to postprandial energy expenditure
Energy expenditure difference from baseline to postprandial (2)
Absolute difference between baseline and postprandial energy expenditure
Thrifty and Spendthrift Phenotypes
Number of infants with a thrifty and spendthrift phenotype
Metabolic flexibility
Difference in respiratory exchange ratio from baseline to postprandial
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