The ICEMAN study: How keeping cool could spur metabolic benefits

June 22, 2014, Garvan Institute of Medical Research

A new study being presented today at ICE/ENDO 2014, the joint meeting of the International Society of Endocrinology and the Endocrine Society in Chicago, demonstrates that ambient temperatures can influence the growth or loss of brown fat in people. Cool environments stimulate growth, warm environments loss.

Brown fat, also known as , is a special kind of fat that burns energy to generate heat. It keeps small animals and babies warm, and animals with abundant are protected from diabetes and obesity. How brown fat is regulated in people, and how it relates to metabolism, have been unclear.

Endocrinologist Dr Paul Lee from Sydney's Garvan Institute of Medical Research, recently undertook The Impact of Chronic Cold Exposure in Humans (ICEMAN) study at the National Institutes of Health (NIH) in Washington, funded as an NHMRC Early Career Research Fellow.

The study results, which clearly show the 'plasticity' of brown fat in humans, are published online today in the journal Diabetes to coincide with the ICE/ENDO meeting.

Lee's previous studies have shown that people with plentiful brown fat stores tend to be lean and have low . His studies have also shown – in the laboratory – that ordinary human white fat cells can change into .

For the ICEMAN study, 5 healthy men were recruited and exposed to four month-long periods of defined temperature – well within the range found in climate-controlled buildings – at the NIH Clinical Centre. They lived their normal lives during the day, and returned each night to the centre, staying for at least 10 hours in a temperature-regulated room.

For the first month, the NIH rooms were maintained at 24º C, a 'thermo-neutral' temperature at which the body does not have to work to produce or lose heat.

The temperature was then moved down to 19º C for the second month, back to 24º for the third month, and up to 27º for the fourth month.

At the end of each month, participants underwent a detailed 'thermal metabolic evaluation' in a whole room calorimeter. Measurements taken at the end of the first month represented 'baseline'.

In addition, cold-stimulated PET/CT scans measured brown fat, and muscle and fat biopsies revealed tissue metabolic changes.

Independent of the season during which the study was carried out, brown fat increased during the cool month and fell during the warm month.

Among the metabolic benefits of increased brown fat was heightened insulin sensitivity. This suggests that people with more brown fat require less insulin after a meal to bring their blood sugar levels down.

"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%."

"During the second thermo-neutral month at 24 degrees, the brown fat dropped back, returning to baseline."

"When we put the temperature up to 27 degrees during the fourth month, the volume of brown fat fell to below that of baseline."

Dr Lee sees promise in brown fat for people with diabetes, whose bodies have to work hard to bring sugar levels down after a meal.

"The improvement in insulin sensitivity accompanying brown fat gain may open new avenues in the treatment of impaired glucose metabolism in the future. On the other hand, 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," 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."

Explore further: Evidence that shivering and exercise may convert white fat to brown

Related Stories

Evidence that shivering and exercise may convert white fat to brown

February 4, 2014
A new study suggests that shivering and bouts of moderate exercise are equally capable of stimulating the conversion of energy-storing 'white fat' into energy-burning 'brown fat'.

Researchers identify specific causes of brown fat cell 'whitening'

April 9, 2014
Boston University researchers have learned new information about the consequences of overeating high-calorie foods. Not only does this lead to an increase in white fat cell production, the type prominent in obesity, but it ...

Key milestone for brown fat research with a ground-breaking MRI scan

April 17, 2014
The first MRI scan to show 'brown fat' in a living adult could prove to be an essential step towards a new wave of therapies to aid the fight against diabetes and obesity.

Newly discovered brown fat cells hold possibilities for treating diabetes, obesity

November 21, 2013
Obesity and diabetes have become a global epidemic leading to severe cardiovascular disease. Researchers at the University of Utah believe their recent identification of brown fat stem cells in adult humans may lead to new ...

Newly discovered human fat cell opens up new opportunities for future treatment of obesity

May 2, 2013
The body's brown fat cells play a key role in the development of obesity and diabetes. Researchers at Sahlgrenska Academy, University of Gothenburg, Sweden, have now discovered that we humans have two different kinds of brown ...

Reducing liver protein SIRT1 levels

January 22, 2014
A new study led by Boston University School of Medicine (BUSM) demonstrates that the abnormal metabolism linked to obesity could be regulated in part by the interaction of two metabolic regulators, called the NAD-dependent ...

Recommended for you

Genetic discovery may help better identify children at risk for type 1 diabetes

January 17, 2018
Six novel chromosomal regions identified by scientists leading a large, prospective study of children at risk for type 1 diabetes will enable the discovery of more genes that cause the disease and more targets for treating ...

Women who have gestational diabetes in pregnancy are at higher risk of future health issues

January 16, 2018
Women who have gestational diabetes mellitus (GDM) during pregnancy have a higher than usual risk of developing type 2 diabetes, hypertension, and ischemic heart disease in the future, according to new research led by the ...

Diabetes gene found that causes low and high blood sugar levels in the same family

January 15, 2018
A study of families with rare blood sugar conditions has revealed a new gene thought to be critical in the regulation of insulin, the key hormone in diabetes.

Discovery could lead to new therapies for diabetics

January 12, 2018
New research by MDI Biological Laboratory scientist Sandra Rieger, Ph.D., and her team has demonstrated that an enzyme she had previously identified as playing a role in peripheral neuropathy induced by cancer chemotherapy ...

Enzyme shown to regulate inflammation and metabolism in fat tissue

January 11, 2018
The human body has two primary kinds of fat—white fat, which stores excess calories and is associated with obesity, and brown fat, which burns calories in order to produce heat and has garnered interest as a potential means ...

Big strides made in diabetes care

January 5, 2018
(HealthDay)—This past year was a busy, productive one for diabetes research and care.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.