Research

Hormonal

Fasting and calorie restriction upregulate UCP2 and UCP3 mRNA expression in human skeletal muscle and adipose tissue, suggesting a metabolic adaptation to energy deficit.

When you restrict calories, your body increases the expression of specific mitochondrial proteins (UCP2 and UCP3) in muscle and fat. This is a normal adaptation to fasting, not a sign that your metabolism is permanently broken. This upregulation happens similarly in both lean and obese individuals, suggesting the regulatory machinery is intact even in obesity.

GoodSupportsHIGH confidence
Calorie restriction induced a similar 2–2.5-fold increase in UCP2 and -3 mRNA levels in lean and obese subjects.
L. Millet et al. · Journal of Clinical Investigation · 1997

Why this rating

Small sample size (n=14 for fasting, n=11 for clamp), but rigorous methodology (RT-competitive PCR, controlled diet).

Source

Increased uncoupling protein-2 and -3 mRNA expression during fasting in obese and lean humans.

L. Millet et al. · Journal of Clinical Investigation · 1997

DOI 10.1172/jci119811

mechanism_only · n=26Cited 354×
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DOI resolved against Crossref · corpus check 2026-06-10

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