How Contrast Therapy Activates Brown Fat (and Why That’s a Good Thing)
By Happi Sauna
You’ve probably heard that contrast therapy—alternating between hot saunas and cold plunges—is great for recovery, stress relief, and mental clarity. But did you know it also activates a special kind of fat in your body that actually burns energy?
Yep, we’re talking about brown fat—and it might just be one of the coolest (and warmest) things happening inside you when you step into the sauna-cold plunge cycle.
Let’s get into it.
First of All: What Is Brown Fat?
Most people think of fat as something we want less of. But not all fat is created equal.
There are two main types:
White fat: This is the typical fat we store for energy—too much of it, and it contributes to weight gain and metabolic issues.
Brown fat (or brown adipose tissue): This is the good kind. It’s metabolically active, packed with mitochondria, and its main job is to burn calories to produce heat. In other words, it turns energy into warmth.
Humans are born with a lot of brown fat (to help keep babies warm), but as we age, we tend to lose it. The good news? Certain activities—like cold exposure—can help us activate and even regrow it.
How Cold Exposure Activates Brown Fat
When you enter a cold plunge after the sauna, your body senses the sudden drop in temperature and kicks into action. One of its first responses is to activate brown fat to generate internal heat.
Here’s what happens:
Cold triggers your nervous system. Your body releases norepinephrine, a hormone that activates brown fat cells.
Brown fat starts burning fuel. It uses glucose and fatty acids to generate heat—raising your body temperature and boosting your metabolism.
You feel more alert and energized. The process not only burns calories but also increases dopamine, giving you that post-plunge high.
Over time, regular cold exposure (especially when paired with heat) can increase both the activity and amount of brown fat in your body—supporting better metabolic health.
What About the Sauna Part?
While cold is the main driver of brown fat activation, sauna use plays a key role too:
Prepping your body: Heat increases blood flow and primes your system for the cold.
Improving adaptation: Alternating hot and cold builds metabolic flexibility—helping your body switch between fuel sources more efficiently.
Helping recovery: Sauna use relaxes muscles, clears metabolic waste, and lowers inflammation—all of which support the benefits of cold therapy.
Together, heat and cold create a metabolic rhythm that your body thrives on.
Brown Fat Benefits (Beyond the Burn)
Here’s why you should care about brown fat—even if you’re not counting calories:
Improved insulin sensitivity
Better thermoregulation (you get less cold in winter!)
Boosted energy and mood
Lower risk of metabolic disorders
And the best part? You don’t need to do anything extreme. Just a few minutes in the cold after a sauna session can make a noticeable difference—especially with consistency.