New research shows that shivering may be more effective than exercise when it comes to burning fat, raising the possibility that people determined to lose weight need only go outside without a jacket to achieve their goal.
Dr. Paul Lee, an endocrinologist at the Garvan Institute of Medical Research in Sydney and lead author of a new study, said in a press release that the new findings build on previous research into so-called brown fat — a type of fat tissue that essentially burns energy instead of storing it. Whereas 50 grams of white fat stores 300 calories, the same volume of brown fat can burn 300 calories in one day. “Excitement in the brown fat field has risen significantly over last few years because its energy-burning nature makes it a potential therapeutic target against obesity and diabetes," he explained. "White fat transformation into brown fat could protect animals against diabetes, obesity, and fatty liver.”
The study, which is published in the journal Cell Metabolism, shows that this fat transformation may be achieved without access to weights or treadmills. By exposing volunteers to cold temperatures and measuring their production of hormones associated with brown fat activation, the researchers found that 10 to 15 minutes of shivering yielded the same increase in production as one hour of moderate exercise. "We identified two hormones that are stimulated by cold — irisin and FGF21 — released from shivering muscle and brown fat respectively,” Lee explained. “These hormones fired up the energy-burning rate of human white fat cells in the laboratory, and the treated fat cells began to emit heat — a hallmark of brown fat function."
Aside from illuminating a potential weight-loss method, these findings also expand the current knowledge of the body’s own heating mechanism. "When we are cold, we first activate our brown fat because it burns energy and releases heat to protect us,” Lee told reporters. “When that energy is insufficient, muscle contracts mechanically, or shivers, thereby generating heat. However, we did not know how muscle and fat communicate in this process."
Shiver, Burn Fat
The current study dovetails with a paper from Maastricht University published earlier this year, in which researchers show that lowering your thermostat may help you burn excess fat continuously throughout your day. According to the authors, it follows that a nationwide move toward lower indoor temperatures may have a tremendous impact on the national health profile. With obesity rates on the rise, an intervention of this scope may prove to be an invaluable service to public health.
While many factors may account for the health benefits of shivering, Lee and his colleagues believe that it all comes down to the fact that heat generation and exercise follow the same physiological rules. "We speculate exercise could be mimicking shivering — because there is muscle contraction during both processes, and that exercise-stimulated irisin could have evolved from shivering in the cold."
Source: Lee P, Linderman JD, Smith S, et al. Irisin and FGF21 are cold-induced endocrine activators of brown fat functions in humans. Cell Metabolism. 2014.