Brown fat, also known as brown adipose tissue, is the healthy alternative to white fat. It burns energy to generate heat, keeping animals and babies warm.
Having an abundant supply of brown fat is also said to protect people from diabetes and obesity. Which is what led endocrinologist Dr Paul Lee to investigate how brown fat could be stimulated in someone’s body.
It turns out being in a cool environment could influence the growth of brown fat, according to a new study led by Dr Lee, who is also a research fellow at Sydney’s Garvan Institute of Medical Research.
"We know brown fat can only be activated in the cold, because if the body is in a temperature-controlled environment it doesn’t need to burn energy to produce heat," he said.
Dr Lee’s past research has shown that people with abundant brown fat stores tend to be lean and have low blood sugar levels. Other studies have also suggested that ordinary human white fat cells can change into brown fat cells.
For this study, published in the journal Diabetes, Dr Lee recruited five healthy males to sleep in a climate-controlled building over a four month-long period. During the day, they lived their normal lives and returned to the building at night for at least ten hours.
Understanding of the role of brown fat – and how to stimulate its growth – could help those with diabetes or obesity.
For the first month, the rooms were kept at a comfortable 24°C, which meant the body didn’t need to work to create or lose heat. To see whether brown fat could indeed grow in cooler conditions, the participants were also exposed to 19°C rooms.
“The big unknown until this study was whether or not we could actually manipulate brown fat to grow and shrink in a human being,” said Dr Lee.
“What we found was that the cold month increased brown fat by around 30-40 per cent.”
However, when the participants stayed in 27°C rooms, their brown fat shrunk.
“When we put the temperature up to 27 degrees during the fourth month, the volume of brown fat fell to below that of baseline,” said Dr Lee.
Dr Lee said greater understanding of the role of brown fat – and how to stimulate its growth – could help those with diabetes or obesity.
He said modern day life, with its comfortable temperature-controlled environments, may well contribute to the obesity epidemic.
“The reduction in mild cold exposure from widespread central heating in contemporary society may impair brown fat function and may be a hidden contributor to obesity and metabolic disorders," Dr Lee said.
“Studies have been performed in the UK and US measuring bedroom, dining room and lounge room temperatures in people’s homes over the last few decades, and the temperature has climbed from about 19 to 22, a range sufficient to quieten down brown fat."
“So in addition to unhealthy diet and physical inactivity, it is tempting to speculate that the subtle shift in temperature exposure could be a contributing factor to the rise in obesity.”
