Ever thought how winter
shivering can help you lose weight and
stay healthy? Yes, it is official – a new study suggests that shivering is as good as bouts of
moderate exercise when it comes to doing away with energy-storing
white fat in your body. In fact, it can trigger the conversion of white fat into energy-burning
brown fat, according to
endocrinologist Dr Paul Lee from
Sydney’s
Garvan Institute of Medical Research. He recently undertook the study at the National Institutes of Health (
NIH) in
Washington.
In case you still find it a bit difficult to digest, let’s get into the heart of the matter. Lee’s work has decoded how fat and muscle communicate with each other through specific
hormones and turn white fat cells into brown ones to protect us from cold. Around 50g of white fat can store more than 300 kilocalories of energy while the same amount of brown fat can burn up to 300 kilocalories a day.
The study, now published in
Cell Metabolism, shows that during cold exposure and exercise, levels of the hormone
irisin (produced by muscle) and
FGF21 (produced by brown fat) rise. In fact, around 10-15 minutes of shivering stimulates
irisin secretion in humans to a point that can only be reached after exercising for an hour on a bicycle at a moderate level. In the laboratory, irisin and FGF21 turn human white fat cells into brown fat cells over a period of six days.
A team from
Harvard University discovered irisin in 2012 through an NIH-funded research project. Irisin has been identified as a muscle hormone stimulated by exercise and it turns white fat in animals into brown fat.
Interestingly, researchers now think that exercise could be a shivering mimic as there is muscle contraction in both processes and exercise-stimulated irisin could have evolved from shivering in the cold.
“Excitement in the brown fat field has risen significantly over the past few years because its energy-burning nature makes it a potential therapeutic target against
obesity and
diabetes,” Dr Lee told the media. “White fat transformation into brown fat could protect animals against diabetes, obesity and
fatty liver. Also, glucose levels are lower in humans with more brown fat.”
All humans are born with brown fat around their necks – a natural protective layer that keeps us warm as infants. Earlier, scientists believed that brown fat would disappear after early infancy, but the notion has now changed. It has been found that most adults carry brown fat and the more you have, the slimmer you are likely to stay. Well, that’s not surprising as more brown fat means higher rate of white fat conversion within your body and more
calorie burning.
Although it is known that
cold temperature stimulates
brown fat formation, Dr Lee has undertaken the current study to pinpoint how the body signals that message to its cells and how the activation of brown fat happens.
The body can sense and relay environmental changes to different organs via nerves and hormones. Being an endocrinologist, Dr Lee has investigated the hormones that are stimulated by cold environments.
“We identified two hormones that are stimulated by cold – irisin and FGF21 – released from shivering muscle and brown fat, respectively. These hormones fired up the energy-burning rate in the laboratory, and the treated fat cells began to emit heat – a hallmark of
brown fat function,” he stated.
According to the
researcher, when we are cold, we first activate our brown fat because it burns energy and releases heat to protect us. When that energy is insufficient, muscles contract mechanically or
shiver, helping raise the hormone level. This, in turn, triggers white fat conversion into brown fat and the calories locked there burn to generate more heat. From a clinical point of view, irisin and FGF21 represent a cold-stimulated hormone system and could be further explored to
fight obesity through
brown fat activation.
Input: Garvan Institute and
Cell Metabolism
Image: Thinkstock Photos/Getty Images
