Francesco Celi of Virginia Commonwealth University was the lead writer of a report about the study. He says irisin has another important role.
Indeed the purpose of brown fat is maintaining the core temperature, so the temperature of the body whereby all the vital functions can be active and normal.
Dr. Celi worked with researchers at the US National Institutes of Health, in Bethesda, Maryland. They already knew the body produces irisin when we do physical exercise. When we exercise, our muscles contract, or change in size, like they do when we shiver. The NIH researchers believe human ancestors developed the ability to shiver as a way to survive cold weather.
This is the last ditch before going into hypothermia and having severe metabolic and life-threatening consequences.
The researchers studied hormonal changes and how the body uses energy in a group of volunteers who exercised. The volunteers were then asked to lie under cooling blankets -- where temperatures were slowly reduced to 12 degrees Celsius.
Most of our volunteers shivered at that time and the shivering was anywhere between five and 10 minutes, not more. And, again we drew the blood before and after the study.
The volunteers bodies produced irisin, but with some surprises.
The amount of increase in irisin was almost identical to what we observed after one hour of exercise. This first set of experiments validated our initial hypothesis, whereby the maximum stimulation of irisin is probably shivering.
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