Better fat for a better body


A diagram od Da Vinci's Vitruvian Man, with brown fat hotspots highlighted.

Calorie-burning brown fat is largely clustered around the head and neck.


In the wake of recent studies, a number of Canadian and international scientists are turning to an unlikely weapon in the fight against obesity, fat. Specifically, they’re looking at brown fat, or brown adipose tissue ( BAT)  that is created when the body shivers, and actually burns energy instead of storing it.

While many scientists have long understood brown fat’s potential benefits, Dr. Paul Lee, of Sydney Australia’s Garavan Institute, took this research a step further earlier this month. Published in Cell Metabolism, Lee’s study shows that by producing brown fat, 15 minutes of shivering may have an equal health benefit to 30 minutes spent on an exercise bike.

Dr. Paul Lee examines results in his Sydney Lab.

Dr. Paul Lee examines results in his Sydney Lab. Lee is the head researcher in the team that discovered the link between the hormone irisin and brown fat and brown fat production.

As unpleasant as a quarter hour of shivering might sound, Lee is quick to point out that he does not mean a fifteen long minutes of straight shivering.

“It’s a continuum,” says Lee from his Sydney office. “When a person started shivering is quite arbitrary. We were looking at the continuous physiological response to cold, and 10 to 15 minutes was sufficient to transform ordinary fat into healthy brown fat.”

During the study, Lee and his team observed ten men and women in a temperature controlled environment. They incrementally dropped the room’s temperature from 27 C to 12 C and gauged how the subjects’ bodies reacted. When they took blood samples, the researchers found that the subjects’ bodies were producing the hormone irisin, which they determined is a direct contributor to brown fat production. A similar test they performed on mice in even lower temperatures showed that the rodents had larger hormone spikes when they shivered more severely.

At the same time, lowering the temperature to an uncomfortable level might be unnecessary. Dr. Lee noted that subjects’ bodies often began releasing brown fat hormones at 19 C, only a few clicks away from room temperature on most thermostats.

To confirm irisin’s connection to brown fat, Lee and the other researchers injected the hormone into lab-grown human fat cells. Soon after, the researchers confirmed that the cells were beginning to produce brown fat.

“The ultimate study would be to administer these hormones to healthy volunteers,” says Dr. Lee. “But of course, we are very far from developing a drug which can mimic those results.”

Brown fat may be grown in muscles as well

There may, however, be another route scientists can take to artificially grow brown fat in the human body. Last year, a team of Canadian scientists led by the Ottawa Hospital Research Institute’s Dr. Michael Rudnicki discovered a way to grow brown fat inside of muscles. This is accomplished by reducing a gene regulator called micro RNA-133 in the muscle’s stem cells, a process that the group has already achieved in mice.

Dr. Lee's team used infrared cameras to detect brown fat in lab tissue

A graphic demonstrating how Dr. Lee’s team used an infrared camera to detect brown fat cells in human tissue. Because brown fat is hotter than white, the temperature sensitive camera is able to detect it.

“We are pretty sure that the mechanics will work in humans,” says Dr. Hang Yin, an OHRI researcher who worked with Dr. Rudnicki on the project. As confident as Dr. Yin is, he admits that humans are much more complicated than mice, and says that “we have to answer a lot of questions before we really think about the application of this.”

Another issue Rudnicki’s team could run into, is that while people probably wouldn’t mind losing some of their excess fat to its calorie burning cousin, the muscle stem cells they would be transforming are important to bodily function. However, Dr. Yin notes that it doesn’t take much brown fat to produce a change. If he were to guess how much brown fat the average human has, Yin puts it below 100 grams, enough to fit in a measuring cup.

Fitness pros use extreme cold to stimulate brown fat growth

Although both of these approaches to growing brown fat have pharmaceutical potential, fitness gurus like Tim Ferriss may have been harnessing its potential for years, without even knowing it. Ferriss is the author of bestseller The 4-Hour Body. In his book, the fitness entrepreneur advocates for daily cold showers and even ice baths to stimulate weight loss.

While Ferriss’ stories may have convinced hundreds, if not thousands, to lower the temperature of their morning showers, Dr. Paul Lee says we need to approach these claims with a grain of salt.

‘There’s no doubt that cold exposure can increase our fat-burning rate and the release of potentially beneficial hormones’ —Dr. Paul Lee

“I would love to say that yes this is a solution,” says Lee. “There’s no doubt that cold exposure can increase our fat-burning rate and the release of potentially beneficial hormones…but the complicating factor is that the body is very good at compensating for lost energy.” In other words, suddenly immersing yourself in ice regularly will likely make you eat more, or cause your body to conserve calories in subtler ways.

“Just like you would not ask an untrained person to run a marathon,” Lee says, “You would not ask a person who is not used to cold to jump into an ice bath.”

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