It’s possible that shivering in the winter cold may have one positive effect… It could be pepping up our metabolism!

A new study, which was recently published in Cell Metabolism suggests that shivering in the cold wakes up a series of biochemical reactions deep within the body, that can alter fat cells and bolster metabolism… the way exercise does.

Scientists with several branches of the National Institutes of Health recruited 10 healthy men and women and had them exercise both intensely and gently while keeping the laboratory at 65 degrees. On their last visit, the researchers had each volunteer lie down for 30 minutes as the lab’s temperature dropped from about 76 to 53 degrees. Towards the end of the session the volunteers were shivering. Blood and other samples were gathered and compared to earlier samples. Specifically, the researchers wanted to see what was happening with the volunteers’ white and brown fat.

While previously it was believed that adult humans do not have brown fat, newer studies have found that brown fat stores in humans of all ages. Unlike white fat it burns calories and generates heat. Chubby babies have lots of brown fat which helps to keep them warm since they’re not very good at shivering. A 2012 study found that animals that made more of a hormone called irisin had more brown fat than other rodents. Irisin was made during muscle contractions, then traveled through the blood to white fat cells where it transformed those cells into calorie-burning brown fat. The study also found that exercise which involves muscle contractions brought on a huge surge in irisin production, and the conversion of white fat to brown fat.

The National Institutes of Health scientists wondered whether irisin production might originally have been brought on by a deeper, older biological process. And, they believe shivering might have been that spark. While the volunteer’s blood levels of an irisin marker were higher after exercise, the markers were just as high after the volunteers had laid quietly in the cold, not moving except to shiver. They concluded that the contraction of muscles, not the exertion of exercise seemed to matter, which happened during exercising and shivering.

So what does this mean? Dr. Francesco S. Celi, a professor at Virginia Commonwealth University, but who, as an investigator at the National Institute of Diabetes and Digestive and Kidney Diseases oversaw the experiments believes irisin originally was created by the muscular contractions that occur during shivering, and exercise increases irisin production not because it’s exercise, but because it’s basically an exaggerated form of shivering.

Dr. Celi adds that there is no indication that exercising in the cold expands irisin production and brown fat compared with working out in warmer temperatures. But, at the very least, if you can’t get to the gym, consider lingering outside in the cold for a few minutes shivering…….     nytimes.com     2/5/14

 

 

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