Dr. Susanna S. Berg is making a deceptively simple argument: cold exposure is a stressor your body was designed for, and we've spent the last century convincing ourselves otherwise. She's not selling extremism. She's reclaiming something ancestral. The research she's conducted puts numbers on what Wim Hof popularized through sheer will — that cold is a training ground, not just for the body, but for the mind.
What I find interesting about Dr. Berg's framing is how cleanly it aligns with what Rhonda Patrick has documented on the cardiovascular side. Patrick's work — drawing on those long-term Finnish cohort studies — shows dose-dependent benefits across metabolic health, mood, and longevity. Berg is arriving at the same destination from a slightly different direction: she's less focused on heat shock proteins and cardiac endpoints, more focused on the resilience cascade that cold specifically triggers. Same mountain, different trail.
The brown fat piece is where Berg adds genuine precision. We know from thermogenesis research that brown adipose tissue is metabolically active in a way white fat simply isn't. It burns calories to generate heat rather than storing them. And cold is the primary signal that wakes it up. People with higher brown fat concentrations have measurably lower BMIs and reduced type 2 diabetes risk — not because of willpower, but because of cellular identity. Cold changes what your fat actually does.
There's broad consensus on the metabolic and cardiovascular benefits at this point. Where you still see genuine disagreement is on timing and dose. Some researchers argue that cold immediately post-exercise blunts hypertrophy by suppressing the inflammatory signal that drives muscle adaptation. Others — and Berg leans this way — see the mental resilience benefits as sufficient justification regardless. The practical answer is probably context-dependent: cold for recovery is different from cold for adaptation.
Start with 30 seconds at the end of your shower. Not as a stunt. As a signal. Your body needs to learn that cold is survivable before it learns that cold is beneficial. Build to two minutes over three or four weeks. Consistency matters far more than temperature or duration. Three times a week, reliably, will outperform seven times a week for two weeks and then nothing.
Here's what I keep coming back to. Dr. Berg says cold is training for the mind, not just the physiology. And when you look at the stress response research — the norepinephrine spike, the dynorphin-endorphin cascade Huberman described — what you're really building is a lower threshold for discomfort tolerance. People who do cold exposure regularly report handling traffic, difficult conversations, and professional setbacks differently. Not because they're tougher. Because they've proven to themselves, repeatedly, that discomfort is temporary and manageable. That's not woo-woo. That's neurological conditioning. The cold is just the training ground.