Newborns expend a lot of energy as they grow. A recent study also estimates that their metabolism is really high compared to that of adults. A witness to cellular activity, the metabolic rate is indeed subject to variations during our lifetime.
Thanks to their growth needs, most children eat in quantity without actually gaining weight. However, according to a study by Duke University (United States) published in the journal Science on August 13, 2021, they would have a higher metabolism . Infants aged nine to 15 months expend 50% more energy, study lead author Herman Pontzer finds over a day than adults in proportion to their body size. Moreover, these same children burn their energy so quickly that one could almost consider them as another species!
In order to reach this conclusion, the researchers analyzed the results of several studies regarding the average calories burned by 6,600 people, including age between one week and 95 years . The technique used for the analysis is that of doubly labeled water, which makes it possible to calculate the total energy expenditure, that is to say the physical activity as well as the basal metabolism.
Scientists say babies are born with the same metabolic rate as their mothers . On the other hand, this rate increases rapidly from the age of nine months. Between nine and fifteen months, babies burn up to 50% more calories than adults. During this period, children triple their weight , which represents a variable playing a certain role in this increase. On the other hand, even without this variable, the energy expenditure is much greater than what the researchers imagined.
After fifteen months, the metabolic rate drops by about 3% each year until the age of twenty. Then, it stabilizes until adolescence , a period that is also characterized by high growth. However, the researchers did not detect any particular increase in metabolism. Finally, the latter begins to decline around the age of sixty at a rather slow rate, namely 0.7% per year.
In toddlers, the acceleration of the metabolism could be explained by the changes occurring in the development of the brain, especially since this organ is particularly energy-intensive. Another study published in 2014 concluded that the brain consumes about 43% of all energy what individuals spend during their childhood.
