Mitochondria (shown above) are tiny structures inside eukaryotic cells that create adenosine triphosphate (ATP), the main source of energy for the cell. That’s why they’re often called “The Powerhouse of the Cell.”
Recent research published in Science suggests that metabolism reaches its peak much earlier in life and declines much later than previously understood. To grasp the significance of this discovery, it’s helpful to define a few important terms.
METABOLISM
Metabolism encompasses all the chemical reactions in the body that sustain life. In humans, this includes transforming energy from food into the fuel needed for essential functions such as breathing, blood circulation, cell repair and growth, digestion, and waste elimination.
BASAL METABOLIC RATE
Basal metabolic rate (BMR) is the minimum energy required to perform these critical processes while the body is resting and fasting. BMR can be estimated using various online tools that consider factors like age, height, weight, and sex. It is sometimes referred to as resting metabolic rate (RMR).
TOTAL ENERGY EXPENDITURE
Total energy expenditure (TEE) is the sum of BMR, energy used for physical activities, and energy required for digesting food—a process called dietary thermogenesis. For adults with a sedentary lifestyle, BMR usually makes up 50% to 70% of total energy expenditure, dietary thermogenesis accounts for 10% to 15%, and physical activity contributes the remaining 20% to 30%.
What Affects Metabolism and What the Latest Study Reveals
Factors like age, sex, body size, body composition, physical activity, and health conditions all play a role in energy expenditure. However, a groundbreaking study with participants from around the globe has provided new insights into how metabolism changes over the course of a lifetime. The results challenge long-held beliefs about how our bodies use energy as we age.
Who Took Part in the Study?
The research involved 6,421 individuals, 64% of whom were women, ranging in age from just 8 days old to 95 years. Participants came from 29 different countries, ensuring a diverse and comprehensive dataset. See What Harvard Scientists Discovered To Be A Shocking New Cause Of Slow Metabolism… And It’s Not What You Think. Watch This 3-Minute Video. CLICK HERE…
The Photo (right) is an x-ray image of an overweight woman with low mitochondria levels compared to a fit woman with high mitochondria levels.
What Did the Study Involve?
To measure total energy expenditure (TEE), researchers used doubly labeled water, a gold standard method for assessing energy use. They also factored in body size, age, and reproductive status using additional datasets and mathematical models. This approach allowed them to identify four distinct phases of energy expenditure over the human lifespan.
What Were the Findings?
The study identified the following key phases of energy use:
Infancy (1 month to 1 year): During the first month, infants’ energy use was comparable to that of adults after adjusting for size. By 9-15 months, energy use surged to nearly 50% higher than adult levels, peaking around 0.7 years old.
Childhood and Adolescence (1 to 20 years): While total energy use and fat-free mass grew steadily with age, size-adjusted energy expenditure declined throughout this period. Interestingly, there was no spike in adjusted energy use during puberty (ages 10-15). By around 20.5 years, energy use stabilized at adult levels.
Adulthood (20 to 60 years): From ages 20 to 60, energy use—including both total and basal metabolic rates (BMR)—remained steady. Even during pregnancy, adjusted energy use stayed consistent, with any increases linked to weight gain. The decline in adjusted energy use began at around 63 years for TEE and 46.5 years for BMR, although fewer BMR measurements make this estimate less certain.
Older Adulthood (60+ years): At around 60, TEE and BMR began to decline alongside reductions in fat-free and fat mass. However, energy declines outpaced what would be expected from body composition alone. By age 90, adjusted total energy use was approximately 26% lower than in middle-aged adults, with annual declines of about 0.7%
What else Did Their Research Find?
The researchers focused on how physical activity and tissue-specific metabolism influence energy use throughout life. Tissue-specific metabolism refers to how some organs, like the brain and liver, consume more energy than others and make up a larger proportion of body weight in younger people. Using various models, they found that changes in activity levels and organ-specific metabolism contribute to total energy expenditure (TEE) at different stages of life. Higher tissue-specific metabolism during early life may support growth and development, while lower energy use in older age may signal a decline in organ-level metabolic function.
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So What is the Take-Home Point of This Study?
This study challenges previously held beliefs that metabolism correlates closely with organ-specific metabolic activity throughout growth and development. Simply put…Havard Scientists have discovered a “6 Second Purple Hack” resulting in rapid weight loss.
As we age, it becomes clear that metabolic changes tied to aging might have a greater impact than we once thought. Interestingly, the findings suggest that weight gain in middle age might not be as closely tied to a slowing metabolism as we often assume.
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