Brown Fat Activation
Brown fat is not as localized in humans as commonly believed; its activation is influenced by overall body temperature regulation. Applying ice packs to the upper back may inadvertently signal the brain to initiate shivering instead of effectively stimulating brown fat. Continuous exposure to cold environments, such as jogging in Arctic conditions, could potentially increase brown fat levels, but the relationship remains under-researched.In this clip
From this podcast

Huberman Lab
Dr. Craig Heller: Using Temperature for Performance, Brain & Body Health | Huberman Lab Podcast #40
Related Questions
How does cold activate brown fat?
What is the effect of being in a cold environment for an extended period of time, rather than a warm one, on a person's brown fat storage as discussed in the episode Dr. Craig Heller: Using Temperature for Performance, Brain & Body Health | Huberman Lab Podcast #40 and the clip Brown Fat Activation?
When exposed to an ice bath and shivering, is it brown fat that gets activated in the episode Dr. Susanna Søberg: How to Use Cold & Heat Exposure to Improve Your Health | Huberman Lab Podcast and the clip Activating Brown Fat?