Which age has the highest metabolism?
Short answer: Infants—especially newborns—have the highest metabolic rate per unit of body weight. Metabolism is also elevated during childhood and puberty for growth, then gradually declines through adulthood as lean mass and growth-related energy needs fall.
Explanation
Basal metabolic rate (BMR) is highest per kilogram in infancy because rapid growth, high brain energy use, thermoregulation, and a large surface-area-to-volume ratio increase energy needs. Childhood and adolescence show elevated total and resting energy expenditure during growth spurts and puberty, particularly in boys who develop more lean mass. After the late teens and into the twenties, BMR typically decreases slowly due primarily to reduced growth and a gradual loss of muscle mass; hormonal changes and lower physical activity further lower metabolic rate with age. Individual metabolism also depends on sex, genetics, body composition (lean mass raises metabolic rate), climate, health conditions, and medications.
Tips
- Preserve or increase lean muscle with regular resistance training to support a higher resting metabolic rate.
- Eat adequate protein to maintain muscle and support metabolic function, especially with age.
- Stay physically active—both aerobic and strength activities raise total daily energy expenditure.
- Get enough sleep and manage stress; sleep loss and chronic stress can lower metabolic efficiency.
- Avoid prolonged extreme calorie restriction, which can reduce resting metabolic rate.
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