Unraveling the Complexities of Energy Expenditure Across the Lifespan
In this blog post we delve into a groundbreaking study that unravels the mysteries surrounding energy expenditure across the lifespan.
Before we begin, what is metabolism again?
At its core, metabolism refers to the total of all the chemical reactions necessary to sustain life, occurring within each of the ~37 trillion cells in our bodies. It involves converting nutrients from the food we consume into energy, creating the building blocks of cells, and eliminating of waste products.
Understanding metabolism involves recognizing the two components of energy balance:
Caloric Intake: This is the energy we get from the food and beverages we consume, measured in calories, which serve as fuel for our bodies.
Total Daily Energy Expenditure (TEE): This accounts for the total amount of energy expended by an individual in a day, encompassing basal metabolic rate (BMR), activity, and digestion.
Unraveling the Complexities of Energy Expenditure Across the Lifespan
Understanding the dynamics of energy expenditure throughout the human lifespan is crucial for tailoring nutrition and health strategies. Recent research by Calorify’s Scientific Advisor, Dr. Herman Pontzer, utilizing the doubly labeled water method, sheds light on distinct changes in TEE and BMR across different life stages (Pontzer et al. 2021). Pontzer and the research team found four distinct stages in human metabolism (controlled for differences in weight).
Fat-free mass– and fat mass–adjusted TEE over the life course (Pontzer et al. 2021).
Infants (birth to 1 year)
Infants exhibit energy expenditures similar to adults in the first month of life but undergo substantial increases in TEE and BMR within the first year. Adjusted metabolic rates peak at approximately 150% of adult levels between 9 and 15 months.
Juveniles (1 to 20 years)
TEE and BMR continue to steadily rise with age, reflecting the growth and development process (surprisingly, so significant increase was found during puberty). Adjusted expenditures decline after 20.5 years, before stabilizing at adult levels.
Adulthood (20 to 60 years)
TEE, BMR, and fat-free mass remain stable during this phase, even during pregnancy. This busts the myth that people experience a metabolic slowdown (and corresponding weight gain) during middle-age!
Older Adults (>60 years)
Both TEE and BMR decline, along with fat-free mass and fat mass. Adjusted expenditures decrease by almost 1% per year, reaching 26% below middle-aged adults for those aged 90 or older.
Implications for Nutrition and Health
Developmental Considerations
Accelerated energy expenditure during the infant and juvenile phases likely relate to the demands of growth and development.
Stable adult expenditures, even during pregnancy, suggest a consistent metabolic rate throughout middle-age, challenging assumptions of age-related weight gain due to declining metabolism.
Aging and Weight Management
The decline in TEE and BEE in older adults highlights potential challenges in weight management.
Understanding metabolic changes in this phase could inform strategies to mitigate the risk of weight gain.
Individual Variability
Interindividual variation in energy expenditure remains considerable, emphasizing the need for personalized approaches in health and nutrition interventions (hence Calorify’s mission of brining these measurements to all!)
As you can see, the insights provided by this doubly labeled water research not only contribute to our understanding of energy expenditure throughout life but also pave the way for more effective and personalized strategies in nutrition and health management.
