Brown fat: MRI scan breakthrough may lead to weight loss ‘holy grail’

For the first time, researchers have identified brown fat in a living human – a find that could lead to development of future weight loss treatments.

Using magnetic resonance imaging (MRI) scans, researchers from Warwick Medical School, University Hospitals Coventry and Warwickshire (UHCW) NHS Trust in Britain, identified the presence of brown fat tissue in a human adult. The existing method, positron emission tomography (PET), identifies active brown fat, but the team’s MRI research shows presence of the actual tissue.

This finding is significant as brown fat may aid future weight loss strategies.

“What most of us imagine is ‘fat’ is actually white fat, which stores [excess] energy and increases in size, [leading to] obesity. But there is another type of fat: brown fat,” study author Thomas Barber, an associate professor in endocrinology and honorary consultant endocrinologist at Warwick Medical School and UHCW NHS Trust, told “What it does is the complete opposite. Instead of storing energy, it actually burns off energy, and in that process, it releases heat.”

When an individual intakes food, most of those calories are used to keep the body functioning – but excess food can’t be destroyed and ends up stored in white fat, or adipose. When brown fat is active, it burns off this excess energy from white fat and creates heat, leading to weight loss.  Temperature, exercise, and elevations of adrenaline and thyroid hormone may lead to activation of brown fat, but, because this is still an emerging field, scientific understanding is still incomplete, Barber said.

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“It’s been estimated that a sugar cube size of brown fat, if activated maximally for a year, could burn its way through 6.6 to 8.8 pounds of white fat during that time,” Barber said. “[You] don’t need to have abundant amounts…if you could find a way of activating the brown fat reserves you have.”

While a PET scan is able to identify active brown fat, the tissue is not always active. The MRI scan findings make way for further research into assessing how to take advantage of brown fat’s function. According to researchers, the MRI scans can potentially be used as indicators for how much brown fat is in an average human adult, once the technology is further developed. Additionally, this research could be utilized for developing new therapies to increase an individual’s brown fat levels.

“It’s real clinical interest is in the fact that this potentially can represent a completely novel mechanism whereby someone can lose weight,” Barber said. “The key, really, is to work out ways of activating the brown fat reserves you have. That’s the question.”

It’s not known how many adults actually have brown fat in their bodies; estimates range from 5 to 50 percent of adults. Until recently it was believed to only be found in babies, between the shoulder blades, and to disappear during early childhood. When brown fat has been identified in adults, it predominantly occurs around the neck and thoracic cavity, within or near white fat. The mechanism by which brown fat develops in a human adult isn’t known, Barber noted.

Currently, there are no existing weight loss therapies that focus on activating brown fat.

“We could now have a potential treatment here, enhancing brown fat activity… which is effectively like taking an exercise pill and using a treatment to enhance metabolic activity…[It’s] literally just burning off excess calories and releasing heat in the process, without actually doing exercise,” Barber said. “It’s almost like the holy grail of the field, to develop such a therapy.”

The research was published in January in The Journal of Clinical Endocrinology & Metabolism.