Dr. Susanna Søberg's work cuts to something most cold exposure content glosses over: brown fat isn't just a curiosity. It's a metabolic organ. One that most of us have largely switched off through decades of climate-controlled comfort. Her core argument is that cold exposure doesn't just make you feel better — it reactivates a tissue your body is designed to use but rarely does in modern life.
That's a meaningful reframe. Most conversations about cold center on mental toughness, dopamine hits, or vague "resilience." Søberg grounds it in cellular biology. Brown fat is dense with mitochondria. When activated, it burns glucose and fatty acids to generate heat — thermogenesis. You're not just shivering through discomfort. You're running a metabolic furnace.
What Søberg adds that Huberman and Rhonda Patrick don't always foreground is the specificity around fat tissue transformation. We know from the sauna literature that heat can convert white fat to beige fat. Søberg's cold research is the other side of that coin — cold activates brown fat directly. Two different temperature extremes, two different mechanisms, both pushing toward a more metabolically active body composition.
The dopamine figure here — a 2.5x increase from cold immersion — aligns closely with what Huberman has documented. But what I find underappreciated is the duration of that effect. Unlike a caffeine spike that crashes, cold-induced dopamine elevates gradually and sustains. It's not a jolt. It's a shift in baseline mood and focus that carries through the day.
There's strong consensus that inflammation reduction is a key mechanism behind cold exposure's benefits — physical and psychological. Søberg's framing of "lower inflammation in the body, lower stress in your brain" is well-supported. The divergence tends to appear around dose and temperature. Some researchers argue brief, moderate cold (15°C for 11 minutes per week) is sufficient. Others push for more frequent, colder exposures. Søberg's own research suggests regularity matters more than heroics.
Three times per week, consistent water temperature below 15°C, two to three minutes minimum. End cold if you're using this in a contrast session — don't fight the rewarming effect. Let your body do the metabolic work of returning to equilibrium. That rewarming period is where brown fat earns its keep.
That statistic about 80% of physician visits being stress-related sits next to the obesity figures in this article, and the connection is rarely made explicit: chronic cortisol suppresses metabolism, drives fat storage, and blunts the dopamine system simultaneously. Cold exposure addresses all three pathways in a single protocol. It's not a treatment for stress or for metabolic dysfunction — but it's one of the few practices that meaningfully signals change to all of those systems at once. That convergence is what makes this worth taking seriously.