THE ROLE OF BROWN FAT ACTIVATION IN CALORIC EXPENDITURE

Abstract

Brown adipose tissue (BAT) plays a crucial role in non-shivering thermogenesis and energy expenditure, making it a promising target for obesity intervention. This study aimed to evaluate the metabolic and molecular effects of cold-induced BAT activation on caloric expenditure and related physiological markers in healthy adults.
For four weeks, participants were evenly assigned to two groups: the first spent all their time in 24°C and the second spent two hours daily in a cooler 16°C.  An indirect calorimeter was used to determine REE and DEXA was chosen to determine body composition.  Blood levels of norepinephrine, FGF21 and retinoic acid were measured using ELISA. From a small group, samples of subcutaneous adipose tissue were taken to identify thermogenic genes (UCP1, PGC-1α) and look at mitochondrial respiration by measuring it.  The findings were examined with T-tests and Pearson’s correlation coefficients.The rise in REE was far bigger in the cold group compared to the control group (mean +180.5 kcal/day, p < 0.05, compared with +42.1 kcal/day in controls).  Serum norepinephrine and FGF21 were markedly higher in the cold group (552.4 pg/mL and 251.2 pg/mL, respectively) than in the control group (388.9 pg/mL and 180.6 pg/mL, p < 0.01).  While mitochondrial respiration improved more than 50% in the cold group (181.3 vs. 120.7 pmol O₂/s/10⁶ cells), the levels of UCP1 and PGC-1α almost tripled.  Every difference reported was meaningful and found to be connected to people consuming more calories.  When it’s cold, BAT becomes active which increases how much energy we use, supports our mitochondria and shifts thermogenic gene function.  The study results strengthen the belief that turning on BAT could be useful in fighting obesity naturally.