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Metabolism Doesn’t Slow Down from Ages 20 to 60
In an August 2021 study published in the journal Science, researchers set out to measure the ebbs and flows of metabolic activity during our lifespans.
They evaluated 6,600 individuals from 29 countries who ranged in age from infancy to 95, measuring their average total daily energy expenditure during each phase of life.
The study—the most comprehensive of its kind—sheds a completely different light on when our metabolic activity peaks and when we burn the most and the least amount of calories during our lifespans.
Researchers found that metabolic activity for humans is the highest in infancy, during the first 12 months of life. In fact, the metabolic rate of babies is 50 percent higher than for adults after adjusting for size and weight. Then, after our first year, our metabolic activity slowly decreases by about 3 percent a year until age 20.
The findings are counter to the common perception that metabolic activity peaks during our early 20s, helping young adults feel invincible. While 20-year-olds can seemingly eat whatever, whenever, and as much as they want, without any undesirable consequences, it turns out it’s not because of an increase in metabolic rate.
Ayurveda and Metabolic Rates
Not surprisingly, this new metabolic map tracks perfectly with what Ayurveda laid out thousands of years ago—that childhood is the most active time, with the highest metabolic rates.
(Once again ancient Ayurvedic wisdom is backed by modern science!)
The Kapha Phase of Life
In Ayurveda, the first phase of life is called the kapha time of life, in which the heavy, calm, moist qualities of kapha (earth and water) predominate. In the same way spring is the kapha season, providing the moisture needed for seeds to germinate and grow, infancy to the late teens are the spring time of human life, in which metabolic activity is needed to grow.
Infants have an extraordinary amount of kapha energy, which makes them flexible enough to grow rapidly, and hungry enough to triple their birthweight in the first year. During the kapha time of life, we produce mucus (or kapha) for a living, making us vulnerable to congestion. We are elastic enough to endure high levels of physical activity, while quickly recovering from injury. As children burn off their baby fat and move into adolescence and the teens, the qualities of kapha begin to wane and the qualities of pitta, or fire, begin to increase.
The Pitta Phase of Life
According to the study published in Science, metabolic activity is stable from ages 20 to 60. There is not a major boost in metabolic activity or in the number of calories required when we’re in our 20s, suggesting that the appearance of a slower metabolism with aging may be more about stress and lifestyle than our metabolic clocks.
During the pitta phase of life, we are still active but stressors can compound, with many of us raising families and finding careers. In the same way, the summer months, or pitta season, have longer days that support a more active lifestyle in preparation for the dormancy of the winter to come.
The Vata Phase of Life
The new study also showed that after 60, metabolic activity slowly starts to decline at about 0.7 percent per year. By age 90, we are burning 26 percent fewer calories than the average middle-aged adult, suggesting that we simply do not need as much food as we get older.
From 60 years old and on is called the vata phase of life, in which the energy of air predominates. Vata, like winter, is dry. The moist kapha qualities that provoked growth in all of us in the first phase of life have run their course.
The biological clocks that regulate cellular aging have slowed down metabolic activity, allowing us to eat less.
At the same time, a lower metabolic rate increases vata, which in turn accelerates physical aging. The mucus membranes that line the inner skin of the digestive and respiratory tracts, as well as the outer skin, begin to dry out more rapidly.
The vata phase of life is like an endless winter. While during the first two phases of life, the body changes gracefully with each season (feeling congested in the spring and hot in the summer, for example), during the vata time of life, seasonal changes are more challenging as dryness, sensitivity and, yes, wrinkles prevail.
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