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Updated: Feb 14, 2026

Infrared Thermography for the Detection of Changes in Brown Adipose Tissue Activity
Published on: September 28, 2022
Seasonal differences in brown adipose tissue density and pulse rate variability in a thermoneutral environment
Shinsuke Nirengi1, Naoki Sakane1, Shiho Amagasa2
1Division of Preventive Medicine, Clinical Research Institute, National Hospital Organization Kyoto Medical Center, 1-1 Mukaihata-cho, Fukakusa, Kyoto, 612-8555, Japan.
Background:
Brown adipose tissue (BAT) is sympathetically activated and induces thermogenesis during cold exposure, thereby influencing energy expenditure and body fat levels. The very low frequency (VLF) components of pulse rate variability could be a form of thermogenic sympathetic nervous activity, but no clear relationship has yet been reported between VLF activity and BAT density. We therefore aimed to evaluate the association between them.
Methods:
We enrolled 20 adults in winter and 20 matched adults in summer. We assessed BAT densities based on total hemoglobin concentrations ([total-Hb]) measured with near-infrared time-resolved spectroscopy. We calculated VLF activity from pulse rate variability measurements.
Results:
BAT density ([total-Hb]; winter 70.5 ± 17.0 μM, summer 57.8 ± 18.3 μM) and VLF activity (winter 6.7 ± 0.8, summer 6.1 ± 0.9) were significantly higher in winter than in summer (P < 0.05). However, there was no significant correlation between VLF activity and BAT density in either season.
Conclusion:
Each parameter exhibited seasonal variation, but we failed to observe any significant correlations.
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