Could Being Cold Actually Be Good for You? Researchers are exploring the health benefits of literally chilling out.

Other labs around the world have tried to figure out if brown fat matters in other ways. In rodent studies, activating brown fat with cold temperatures has been found to regulate fatty acid and glucose levels. That led some researchers to suspect that the tissue can help protect against dysfunctional glucose processing in diabetes and fatty acid processing in obesity. So far, some studies in adult people have linked brown fat’s presence to leanness and normal blood sugar. (In 2013, WIRED covered an independent researcher’s quest to harness brown adipose for weight loss.) But it’s not as simple a proposition as braving a little cold, tacking on some brown fat, and then losing weight. The story is a bit more complicated. After the brown fat discoveries in 2009, Joris Hoeks, a diabetes researcher at Maastricht University in the Netherlands, was curious about its role in controlling blood sugar. His team recruited people with type 2 diabetes for a cold acclimation study. An important hallmark of type 2 diabetes is insulin resistance, in which organs take up less sugar from the blood. Participants endured six hours of cold, right on the edge of shivering, for 10 days. Their sensitivity to insulin, a key hormone in controlling blood glucose, improved by 43 percent on average—a boost comparable to the effect of a 12-week workout program. “We thought, ‘OK, that's a great result,’” Hoeks recalls. The cold seemed to have caused the change in insulin response. But there wasn’t a clear connection to brown fat activity. “It was stimulated by the cold, but not much,” he says. So Hoeks’ team doubled down. In a study published in March 2021, they repeated the test but took precautions to avoid all shivering by raising the temperature and giving the subjects extra clothing if needed. In these conditions, mild cold acclimation caused no improvements in glucose regulation or fat metabolism. Instead, the results from this pair of studies point to changes in muscle as more important for diabetes than brown fat. Muscle cells change in the cold. Proteins responsible for transporting glucose fuel into muscle cells appear to migrate toward the outside of the cell. Hoeks thinks that change may help the body process more glucose, either because of mild or unnoticeable shivering contractions, or some other muscle process altogether. “We don't know what it is,” he says. “Cold works, it really works. But it’s not going through brown fat” to make diabetics more sensitive to insulin, Hoeks says. Other studies have shown that muscle is in fact responsible for metabolizing about 50 times more glucose than brown fat because muscle is so much more prevalent in the body. And Haman agrees that muscle cells are likely very important in regulating blood sugar. “If I'm doing this, all day,” Haman says, flexing his bicep with a couple of quick curls, “I'm likely using way more glucose and fatty acids than what brown fat would be.” So far, the evidence seems to support Haman and Hoeks’ hunches that cold acclimation is good for people—but there’s still much more to learn. For Haman, the next step is to try to factor in dietary restrictions. In the future, he’d like to figure out how cold exposure and calorie restriction affect weight loss. One group will restrict their diet, another will do that in the cold, and another will just be cold. The study will track how much weight they lose. But, of course, Haman says, recruiting volunteers will be a slog: “How easy do you think it's going to be to recruit the people that are just going to do cold exposure for nine weeks?” https://www.wired.com/story/could-being-cold-actually-be-good-for-you/