Story perspectives

1.9% of Americans: The Hidden Struggles of Constitutionally Thin

9/5/2025

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Summary

Story summary

Researchers estimate 1.9% of the population, or 6.5 million in the U.S., is "constitutionally thin."
These individuals maintain a normal diet but have a body mass index below 18.5, facing social stigma.
They typically have normal fat levels but reduced muscle mass, raising concerns like osteoporosis.
Some may lose up to 10% of ingested calories through fidgeting or increased excretion.
Ongoing research, including a study at the University of Copenhagen, explores metabolic and genetic factors.

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Story summary

Researchers estimate 1.9% of the population, or 6.5 million in the U.S., is "constitutionally thin."
These individuals maintain a normal diet but have a body mass index below 18.5, facing social stigma.
They typically have normal fat levels but reduced muscle mass, raising concerns like osteoporosis.
Some may lose up to 10% of ingested calories through fidgeting or increased excretion.
Ongoing research, including a study at the University of Copenhagen, explores metabolic and genetic factors.