Good fat is the brown type, while the fat nobody likes is the white type. Brown fat keeps us warm by burning energy, white fat on the other hand, stores energy and widens waists and thighs and enlarges our bottoms.

A group of scientists at The University of Texas Health Science Center is carrying out research into brown fat with the aim of tackling obesity.

At the molecular level, distinguishing brown from white fat is difficult for researchers, making it harder from them to make any meaningful scientific progress into really understanding the mechanisms of obesity.

Senior investigator, Mikhail Kolonin, Ph.D., and colleagues set out to see whether they could find a way of telling brown fat from white fat rapidly in the human body. Ultimately, so that doctors could help devise more effective treatments for obesity.

According to a report published in the journal Nature Communications, they successfully developed a brown fat detection method in an animal model.

Dr. Kolonin explained:

Brown adipose tissue (fat), responsible for heat generation, has high importance in the context of metabolic diseases. Brown fat is more common in children but has recently been discovered in adult humans. However, measurement of its body distribution has remained technically challenging. We report a peptide probe that zeroes in on brown fat and can be used for localization of this tissue in mice by whole body imaging.”

The study authors believe that if this brown fat detection method works in human studies, it would help doctors calculate their patients’ brown-to-white fat ratios and devise targeted treatments based on individual cases.

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Brown fat (brown adipose tissue) is especially abundant in newborns.

Kolonin said “This is the first targeted imaging approach for the detection of brown fat.”

Kolonin and Eva Sevick-Muraca, Ph.D., a medical imaging researcher, together developed a near-infrared fluorescence imaging probe that binds to the brown fat in the blood stream. It emits tiny amounts of light that penetrate through the skin and can be picked up by ultra-sensitive cameras.

The probe is a peptide, a series of amino acids linked together in long molecular chains. After trying out several different peptides, the team found one that could selectively localize to brown fat when administered into the blood stream.

The researchers then added a dye to the peptide so that it could be detected during whole body scans.

In an Abstract in Nature Communicaitons, the authors concluded “Finally, we demonstrate that this probe can be used to identify brown adipose tissue depots in mice by whole-body near-infrared fluorescence imaging.”

Brown fat, also known as brown adipose tissue (BAT), is one of two types of fat mammals (including humans) have. The other type is white (yellow) fat.

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Brown fat is concentrated in the upper chest and neck.

White fat builds up around the thighs and waist, while brown fat is concentrated in the upper chest, and the front and back of the neck.

Obese individuals and patients with type 2 diabetes have a lower percentage of brown fat than other people.

Newborn babies and mammals in hibernation have high levels of brown fat. Approximately 5% of a human newborn’s body weight is made up of brown fat. As the baby gets older, the percentage drops.

Brown fat has one main function – to generate body heat, to keep us warm. However, scientists emphasize that our knowledge about what brown fat does is limited – brown fat probably has several functions we do not know about yet.

White fat cells (adipocytes) have a single lipid (fat) droplet, while brown adipocytes have many lipid droplets. Brown adipocytes have many iron-containing mitochondria. Brown fat’s high iron content gives it its dark red or tan color.

Brown fat consumes more oxygen than white fat, hence it has more capillaries.

Should we try to raise brown fat levels? – according to researchers, nobody knows whether raising brown fat levels in humans is possible, or even recommendable.

Researchers at the Universite de Sherbrooke in Canada found that when people were exposed to cold temperatures, their brown fat cells ‘turned on’. They also found that people whose brown fat cells were active were burning calories at a much higher rate.