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‘Efficiency savings’ may spark energy expenditure declines during puberty
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Both boys and girls experience a decline in resting energy expenditure during puberty, with girls experiencing a greater reduction, according to results from a 10-year longitudinal study.
“The decline in absolute [resting energy expenditure] at a time of rapid growth ... is counterintuitive because body mass is deemed the single most important determinant of [resting energy expenditure],” Mohammod Mostazir, MSc, a research fellow in medical statistics within the Biomedical Informatics Hub of University of Exeter, and colleagues wrote. “However speculative, we believe that the decline in intrinsic energy expenditure shown here may represent a period of programmed energy conservation (‘efficiency savings’), which has evolved to [ensure] the extra energy needed for adolescent growth.”
Mostazir and colleagues analyzed data from 347 children participating in EarlyBird, a nonintervention, longitudinal study of healthy school children reviewed every 6 months as a single cohort from age 7 to 16 years in Plymouth, United Kingdom. Researchers measured voluntary energy expenditure as physical activity recorded by accelerometer, involuntary energy expenditure as resting energy expenditure (REE) indicated by oxygen consumption, BMI and body composition via annual DXA scans. Researchers used mixed-effects modeling to analyze trends in REE and its relationship to BMI, lean mass, fat mass, age, physical activity and pubertal stage.
Researchers observed a progressive decline in physical activity from age 7 to 16 years in both sexes that accelerated with age, with a greater decline observed in girls.
In an unadjusted model, REE rose in children until age 11 years, after which it fell in girls and boys until age 15 years, when it rose again, according to researchers. The fall coincided with a period of pubertal growth from age 11 to 15 years, they wrote, during which girls gained fat mass and boys gained more lean mass.
The researchers noted that the decline in REE could not be explained by fasting insulin, adiponectin, leptin, luteinizing hormone or follicle-stimulating hormone levels.
“Metabolism falls sharply during puberty, which could explain why adolescents are particularly vulnerable to weight gain,” Terence Wilkin MD, professor of endocrinology and metabolism at the University of Exeter Medical School, told Endocrine Today. “The fall in metabolism may be a throwback to earlier times when energy conservation was important to [ensuring] pubertal growth. Understanding its mechanism could mean it might be prevented pharmacologically at a time when calories are plentiful.” – by Regina Schaffer
Disclosure: The researchers report no relevant financial disclosures.
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