Winter is almost here.

Despite what you may have heard from Christmas carolers, it’s not always the most wonderful time of the year: Iced-in cars, chapped lips, soggy shoes, and frozen fingers are what we can all look forward to over the next few months—and I live in California.

I would feel sorry for all you poor saps in the snow, but at least there might be a silver lining to eking out an existence in frigid temps: Cold could be a key to losing weight.

The theory isn’t exactly new. Cryotherapy—the latest “health” craze that promises customers the chance to freeze themselves thin by spending three-minutes in temperatures below -256 degrees Fahrenheit—adds to the tactics used by diet gurus and celebrities who have relied on cold for years.

Until now, though, there wasn’t much word from the scientific community about the validity or process. But, according to a new study published in the research journal Cell, cold can change your body composition—but it all comes down to microbes.

The tiny organisms that live in and on your body are symbiotically responsible for most bodily functions. Manipulating the microbiome—or, the communities of microbes—has been linked to all sorts of health benefits, from battling gut diseases to alleviating arthritis, but the science is complicated and researchers around the world are still working to understand the hows and whys.

In this study, led by Swiss physiologist Mirko Trajkovski at the University of Geneva, scientists used mice to determine how cold changes the microbiome and how that change impacts metabolism. Building on past research that showed altering the microbiome affects the body’s ability to regulate temperature, the team took microbial samples from the mice and then turned down the heat.

Living in 59 degrees Fahrenheit, the mice experienced a drop in body temperature. The researchers then collected stool samples and began measuring insulin and fat levels. They found that the cold mice had increased sensitivity to insulin, lower blood sugar levels and, sure enough, they began to burn more fat.

Meanwhile, their microbes were changing—especially one commonly associated with obesity and diabetes called Akkermansia muciniphilia, which was all but eliminated.

After about a week of being in the cold, however, the researchers found that the intestines in the mice had elongated, increasing the gut surface, and making caloric absorption more efficient.

The scientists tested the bacterial connection to these changes by transplanting a the microbiome from a cold mouse into other mice. After receiving the transplant, the mice dropped weight, their blood sugar lowered and, like their cold counterparts, their intestines extended.

“We found that these changes favored enhanced energy extraction during cold,” the researchers write. They explain in the discussion portion of the paper that the changes in the gut require more energy output and that A. muciniphilia may be an important microbe for energy regulation:

“All this suggests that this bacterium may act as an energy sensor that is abundant during caloric deficiency and is low when the energy is in excess, as a co-evolutionary mechanism enabling the energy uptake when available.”

The findings have shed light on one aspect of physiological adaptation to the cold—and on the role the microbe A. muciniphilia plays in obesity, which could lead to better treatments in the future. For now though, the science is still in development. The tests done in mice don’t necessarily confirm what might be happening in humans.

Still, doesn’t mean you can’t enjoy the winter, knowing that you might be shivering your way to that summer beach bod—just as long as you don’t get too carried away. As Elizabeth Pennisi writes in Science:

“Whether these results apply to humans is a big ‘if,'” Trajkovski cautions. “But you should not overdo it.”