In this post, we’ll break down what happens inside your body when you get cold and how it might help you feel and function better.
What Is Cold Therapy?
Cold therapy means using cold temperatures to help the body in different ways. This can include ice baths, cold showers, or just spending time in chilly weather.
At first, it might seem like something to avoid. But when your body feels cold, it starts working harder. This extra work affects your muscles, fat, hormones, and nervous system. All of these things play a big part in how your body uses energy.
Brown Fat: Your Body’s Built-In Heater
Brown fat, also called brown adipose tissue, is different from the white fat most people think of.
Brown fat burns energy to make heat. It does this using a protein called UCP1. This protein helps your cells burn fat and sugar without making energy (ATP). Instead, the energy turns into heat.
Cold is the main way to turn on brown fat. When your skin senses cold, your nervous system sends out a signal. This signal tells brown fat to start working. The result is more calories burned and better blood sugar control.
Turning White Fat Into Beige Fat
Most fat in the body is white fat. It stores extra energy and doesn’t do much else.
But cold therapy can change how some of that white fat works. Under the skin (subcutaneous fat), white fat can start acting more like brown fat. This is called beiging.
When this happens:
- White fat creates more mitochondria
- It starts to burn more energy
- It produces more heat
- It supports better insulin function
That’s a big shift. Your body turns stored energy into heat, helping you stay warm while also using up fuel.
Muscle and Shivering: Moving Without Exercise
If you get cold enough, your muscles will start to shiver. This is called shivering thermogenesis.
Shivering makes your muscles contract and relax quickly. That takes a lot of energy, mostly from sugar (glucose). It’s like your body is working out, even though you’re not moving much.
Muscle also releases a hormone called irisin during shivering. Irisin tells fat cells to burn more energy, too. So muscle and fat are working together to warm you up and improve your metabolism.
Cold-Triggered Hormones That Help Your Metabolism
When your body gets cold, it releases hormones. These hormones help your tissues communicate and work better together.
Here are a few important ones:
- Irisin – Comes from muscle. Activates brown fat and helps white fat become beige.
- FGF21 – Comes from muscle and fat. Increases fat burning and improves insulin sensitivity.
- Adiponectin – Comes from fat. Lowers inflammation and helps your body use insulin better.
These hormones play a big role in how your body handles food, especially sugar and fat.
Cold Exposure and the Nervous System
Your nervous system has two main parts when it comes to stress and recovery:
- Sympathetic (fight or flight)
- Parasympathetic (rest and digest)
Cold therapy wakes up your sympathetic system. It raises your heart rate and helps you burn fat. But with regular practice, cold can also boost your parasympathetic system. That helps you recover and stay calm.
This balance between the two is called nervous system flexibility. It’s important for overall health and stress control.
Best Ways to Try Cold Therapy
Not all cold methods are the same. Some are easier to do. Others have stronger effects.
Here are a few common types, listed from least to most effective for metabolism:
- Face in cold water – Calms the nervous system, but not much metabolic change
- Cold shower – Easy, but short-lived effects
- Being outside in the cold – Helps if you start to shiver
- Cryotherapy chambers – Expensive and short exposure, with moderate results
- Cold water immersion (ice bath) – Most effective method for activating brown fat and shivering
If you’re just starting, a cold shower or a walk in cool weather is a simple place to begin. For the biggest changes, full-body cold water immersion works best.
Final Thoughts
Cold therapy helps your body use energy in smart ways. It can:
- Burn more calories
- Improve insulin sensitivity
- Boost hormone function
- Strengthen your stress response
Even short cold exposure can make a difference, especially if done regularly. As with any health practice, start slowly and see how your body responds.