Research

Hormonal

In humans, circulating FGF21 exhibits a circadian rhythm with a nocturnal rise peaking in the early morning, and this pattern is driven by oscillations in free fatty acids (FFAs) which stimulate hepatic FGF21 expression via PPARα activation.

This paper establishes that FGF21, a hormone regulating energy metabolism, rises naturally at night in humans, driven by free fatty acids. For obese individuals, this natural nocturnal rise is blunted. While this paper does not prescribe a specific intervention, it suggests that maintaining healthy fatty acid levels (via diet/exercise) may support this natural circadian rhythm, which is disrupted in obesity.

GoodSupportsHIGH confidence
These findings support the role of FGF21 as an important metabolic regulator that integrates the circadian rhythm with energy homeostasis in humans. Diurnal rhythms of circulating FGF21 could be partly caused by the oscillation of free fatty acids.
Haoyong Yu et al. · Clinical Chemistry · 2011

Why this rating

The study uses a rigorous 24-hour sampling protocol (every 30 mins) in humans, combined with in vitro validation, though the sample size is small (n=36).

Source

Circadian Rhythm of Circulating Fibroblast Growth Factor 21 Is Related to Diurnal Changes in Fatty Acids in Humans

Haoyong Yu et al. · Clinical Chemistry · 2011

DOI 10.1373/clinchem.2010.155184

cohort · n=36Cited 166×
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DOI resolved against Crossref · corpus check 2026-06-10

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