An international team of investigators has released the first-ever study examining total energy expenditure over the course of the human lifespan, shedding light on human development and aging.
The findings, published in Science, suggest that weight gain and development of obesity is largely due to increased caloric intake rather than a reduction in metabolism, said Robert Kushner, MD, ’80, ’82 GME, professor of Medicine in the Division of Endocrinology, of Medical Education and a co-author of the study.
The body consumes a certain amount of calories every day, which is essential for proper body functioning and development. Nonetheless, how total daily energy expenditure — the number of calories an individual burns in one day — changes over the course of one’s life has remained understudied, according to the authors.
To determine its trajectory, the investigators studied a database of total energy expenditure data from 6,500 men, women, children and newborns around the word, ranging in age from 8 days to 95 years of age. The data was captured using the doubly labeled water method — a non-invasive, isotope-based technique that estimates an individual’s caloric intake and expenditure as they go about daily activities.
After normalizing the data for fat-free mass — internal organs, bone, muscle, water and connective tissue, for example — the investigators found that change in total energy expenditure goes through four phases during one’s lifespan.
In newborns, total energy expenditure increased up to one year of age, and in children, it also increased from 1 to 20 years of age. In adulthood, however, it stabilized from ages 20 to 60 years and then declined in older adults ages 60 years and older.
The findings challenge a long-held belief that energy expenditure begins to decline in early or mid-adulthood, according to Kushner, adding that the data will also help healthcare providers create more informed and patient-centered nutrition plans and care strategies.
“The data strengthens our counseling goals of encouraging patients with obesity to consume a healthy diet that is calorie restricted. It also highlights the importance of recommending an active lifestyle and exercise to maintain healthy aging,” Kushner said.
This study was supported by the International Atomic Energy Agency, Taiyo Nippon Sanso and SERCON.
