At the yearly Rottnest Channel Swim in Western Australia, participants often smear their bodies with animal fat for insulation(36) the 70-degree water. But their own body fat also helps to keep them warm, like an extra layer of clothing (37) the skin. When scientists studied aspects of the event in 2006, they found that swimmers (38) a greater body mass index (BMI) appear to be at much (39)risk of getting hypothermia. Under certain conditions, though, overweight people might feel (40) than people of average weight. That’s because the brain combines two signals—the temperature (41) the body and the temperature on the surface of the skin—to determine when it’s time to constrict blood vessels (which (42) heat loss through the skin) and trigger shivering (which (43) heat). And since subcutaneous fat traps heat, an obese person’s core will tend to remain warm (44) his or her skin cools down. According to Catherine O’Brien, a research physiologist with the U.S. Army Research Institute of Environmental Medicine, it’s possible that the lower skin temperature would give (45) people the sense of being colder overall.
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