When was a graduate student at the University of Michigan, he struggled through frigid, snowy winters. Shivering each time he ventured into the early evening darkness, he wondered: Why can animals like squirrels and bears seemingly adapt to cold environments, while he had to suffer?
This question set Kajimura on the hyper-specific path to becoming a leading researcher on cold exposure and energy metabolism. Through his decades of study, Kajimura that not only can humans adapt to the cold — they can thrive in it.
Other jibes with his work, suggesting cold weather can actually supercharge exercise and help people
- Burn energy more efficiently
- Cause “bad” white fat to act like metabolically beneficial brown fat
- Enable longer more efficient workouts.
Chilly activities also help people stave off the winter blues, get their dose of vitamin D, and enjoy nature.
“If you combine cold and exercise, it has an additive or even synergistic effect,” Kajimura tells Inverse. “But how this synergy works at the molecular level is not really clear.”
The science doesn’t encourage stripping down to a tank top and shorts in freezing temperatures — actions that can increase the risk of hypothermia. And if you have any risk of cardiovascular disease, cold-weather workouts also aren’t recommended, Kajimura cautions.
However, if you are healthy, stretch, and gear up appropriately, you don’t have to let the winter months lock you inside. Staying active in all seasons will spur positive side effects that last long after spring arrives.
Is it healthy to exercise in winter?
To fully grasp how humans deal with cold, you have to understand – the body’s built-in, self-regulation mechanism that maintains stable internal conditions optimal for survival.
Humans’ core body temperature is 37 degrees Celsius, or 98.6 degrees Fahrenheit. To keep our internal machines running smoothly and achieve homeostasis, the body favors operating at this temperature. In turn, when we’re overheated, we sweat. When we’re chilly, we shiver.
Sweating doesn’t dissipate energy — it’s just a way for our bodies to cool off. However, shivering requires energy and produces heat.
“In a cold environment, at rest, we burn more calories than we do in normal temperatures,” David Rogerson tells Inverse. is a sports nutritionist and strength conditioning expert at Sheffield Hallam University.
The science of fat burning — If you’re interested in increasing energy expenditure or losing weight, Kajimura says: “It makes a lot of sense to exercise in the cold.”
Why? For about the first 10 to 30 minutes of cold exposure, muscles shiver to make heat. But it isn’t possible to shiver indefinitely, because lactic acid builds up in the body.