This narrative review discusses low-intensity RF-EMF exposure, primarily from mobile phones, with a focus on thermoregulation and energy homeostasis. It reports that many rodent studies at 900 MHz describe cold-like thermoregulatory and behavioral responses and molecular findings suggestive of WAT browning, while BAT transcriptional changes typical of cold exposure were not observed. The authors indicate short-term adaptations may not disrupt homeostasis, but emphasize uncertainty about long-term consequences and call for further research, including at 5G-relevant frequencies.

This animal study measured core body temperature in free-moving male and female Sprague Dawley rats during and after 3-hour exposure to 1.95 GHz RF-EMF at multiple whole-body average SAR levels. A measurable thermal response was reported at 4 W/kg, while lower SAR conditions showed smaller or no significant temperature increases. The authors note that temperature dropped quickly after exposure ended, implying post-exposure measurements may underestimate peak heating.

In a rat experiment (n=59), a single 40-minute whole-body 28 GHz exposure at near-threshold WBA-SAR levels was evaluated under normal and heat conditions with restraint. After accounting for sham-related restraint stress, exposure was associated with increased serum-free corticosterone 1–3 days later, especially when rectal temperature rose by >1°C. Urinary catecholamines suggested an immediate inhibitory effect on stress response (notably noradrenaline), with heat amplifying effects and linking noradrenaline to tail surface temperature.

This animal study exposed juvenile and young adult Wistar rats to 5G (3.5 GHz) or 2G (900 MHz) radiofrequency fields (1.5 V/m) for 1–2 weeks and measured brown adipose tissue-related gene expression by RT-qPCR. The abstract reports significant downregulation of PRDM16 and C/EBP mRNA after 5G exposure, while UCP1-dependent thermogenesis markers were not significantly changed at the transcriptional level. The authors interpret these findings as a potential partial disruption of brown adipocyte differentiation and raise EMF safety concerns, while calling for further confirmatory research.