Rapid growth demands immense energy from newborns. A landmark Duke University study, published in Science on August 13, 2021, reveals infants have a strikingly higher metabolism than adults—a direct measure of cellular activity that shifts across the lifespan.
Children often eat voraciously to fuel growth without excessive weight gain. Yet, lead researcher Herman Pontzer's analysis shows infants aged 9 to 15 months burn 50% more energy daily than adults, adjusted for body size—making their metabolic rate rival another species.
The team reviewed data from 6,600 participants aged one week to 95 years, using the gold-standard doubly labeled water method to precisely measure total energy expenditure, including physical activity and basal metabolic rate.
Babies start life with a metabolic rate matching their mothers', but it surges from 9 months onward. Between 9 and 15 months, they expend up to 50% more calories than adults, even as they triple their body weight—a factor that amplifies but doesn't fully explain the phenomenon.
Post-15 months, metabolism declines ~3% annually until age 20, then stabilizes through adolescence despite growth spurts. It begins a gradual drop around age 60 at 0.7% per year.
In infants, the spike likely stems from brain development, an energy-hungry organ. A 2014 study found the brain accounts for about 43% of total energy use in early childhood.
