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Brown Fat, White Fat, Good Fat, Bad Fat

Posted on by Dr. Francis Collins

Photo of adipocytes in white adipose
Caption: Brown fat cells (stained brown with antibodies against the brown fat-specific protein Ucp1) nestled in amongst white fat cells.
Credit: Patrick Seale, University of Pennsylvania School of Medicine

Fat has been villainized; but all fat was not created equal. Our two main types of fat—brown and white—play different roles. Now, two teams of NIH-funded researchers have enriched our understanding of adipose tissue. The first team discovered the genetic switch that triggers the development of brown fat [1], and the second figured out how the body can recruit white fat and transform it into brown [2].

Why would we want to change white fat into brown? White fat stores energy as large fat droplets, while brown fat has much smaller droplets and is specialized to burn them, yielding heat. Brown fat cells are packed with energy generating powerhouses called mitochondria that contain iron—which gives them their brown color. Infants are born with rich stores of brown fat (about 5% of total body mass) on the upper spine and shoulders to keep them warm. It used to be thought that brown fat disappeared by adulthood—but it turns out we harbor small reserves in our shoulders and neck.

In mice, brown fat does something remarkable: it burns more calories when mice are overfed, protecting them from obesity. (Don’t you wish eating a plate of fries did that for you?) Furthermore, mice genetically predisposed to have with extra brown fat are actually leaner and healthier. In humans, there is evidence that more brown fat is associated with a lower body weight. So, how might we increase our brown fat production?

The team led by the University of Pennsylvania figured out the switch for creating a brown fat cell—a protein called early B cell factor-2 (Ebf2). Comparing the active genes in brown and white fat cells, they discovered Ebf2 is present in larger quantities in brown fat. This protein seems to mark which genes will later be turned on to transform certain types of precursor cells into brown fat. When the team engineered mice lacking this protein, the animals had white fat cells on their upper back and spine rather than the typical brown. When the team expressed high levels of Ebf2 in white fat, these cells turned brown and consumed more oxygen—a sign they were producing more heat.

The second team, led by Harvard’s Joslin Diabetes Center, noted that mice have two types of brown fat: constitutive brown fat, which they have from birth, and “recruitable” brown fat, scattered throughout the muscles and white fat. When researchers engineered mice lacking a protein called Type 1A BMP-receptor (BMPR1A)—which is needed for the correct development of brown fat—the mice were born with just a tiny bit of constitutive brown fat on their back.

You would think that these mice would be terribly cold. Surprisingly, they kept a normal body temperature. How did they manage this feat?

The lack of brown fat apparently sends a signal via the brain to the recruitable fat cells, telling them to make the switch and transform into brown fat. The mice stayed warm, and the recruited brown fat even protected them from obesity.

In humans, too much abdominal white fat promotes heart disease, diabetes, and many other metabolic diseases. It would be potentially therapeutic if we could transform some of our white fat into brown. Determining which genes control the development of white and brown fat may be the first step toward developing game changing treatments for diabetes and obesity.


[1] EBF2 determines and maintains brown adipocyte identity. Rajakumari S, Wu J, Ishibashi J, Lim HW, Giang AH, Won KJ, Reed RR, Seale P. Cell Metab. 2013 Mar 12

[2] Brown-fat paucity due to impaired BMP signalling induces compensatory browning of white fat. Schulz TJ, Huang P, Huang TL, Xue R, McDougall LE, Townsend KL, Cypess AM, Mishina Y, Gussoni E, Tseng YH. Nature. 2013 Mar 13

NIH support: the National Institute of Diabetes and Digestive and Kidney Diseases; and the National Institute of General Medical Sciences


  • Mary Szabo says:

    Extremely interesting article given the increase prevalence of obesity. It would also be interesting to see whether lifestyle can have any influence on the expression of these genes once when they are being identified.
    Will definitely stay tuned.

  • Jorge Luis Prosperi says:

    How could we transform some of our white fat into brown?
    Thanks for your answer and warm regards,
    Jorge Luis Prosperi

    • Moderator says:

      Thanks for your question, Jorge Luis. The work highlighted by Dr. Collins involved genetically engineered mice. So, more research needs to be done before we can consider transforming white fat into brown fat in humans.

  • James Apesos, MD says:

    So liposuction removes white fat? Is that good? Seems to me that your article does not tell us how to get more brown fat.

    • Moderator says:

      Good question, James! Because the studies mentioned in this blog post were done in genetically engineered mice, they tell us very little, if anything, about the health effects, good or bad, of liposuction in humans.



  • Lawrence Zendle says:

    Looking for a ‘game changing’ treatment for diabetes and obesity? You don’t have to wait for any pie-in-the-sky gene therapies, either. Rather, you can read right now the study that was published May 2009 in The American Journal of Clinical Nutrition, Dr. Neal Barnard as principal investigator, entitled ‘A low-fat vegan diet and a conventional diabetes diet in the treatment of type-2 diabetes; a randomized, controlled 74-week clinical study:

    • Moderator says:

      Thanks for sharing this study, Lawrence. For anyone who might be interested,the study’s conclusions were as follows:

      Both diets were associated with sustained reductions in weight and plasma lipid concentrations. In an analysis controlling for medication changes, a low-fat vegan diet appeared to improve glycemia and plasma lipids more than did conventional diabetes diet recommendations. Whether the observed differences provide clinical benefit for the macro- or microvascular complications of diabetes remains to be established. This trial was registered at as NCT00276939.

    • Leigh says:

      I know someone who did that diet and ended up in the hospital with glucose at 800. Protein is critical.

  • Irene Skibinsky says:

    My brother and sister-in-law have been on the Dr. Atkins Diet for almost two years, now on the maintenance portion. Both have eliminated body fat, high cholesteral levels and abdominal fat! She has reduced her dependence on insulin, now considered non-diabetic. At 67, they are both healthy. How can this be explained?

    • Leigh says:

      Protein, veggies, complex carbs. It’s very good, some people call it Paleo. Oh, and GOOD fats like olive oil.

  • kalpana parekh says:

    nice to know about brown fat , would like to know more on how to make white fat to brown fat ASAP, please inform.

  • Michael Gregory says:

    Interesting, nice lunch time read, as I stuff my face with bacon cheeseburger and fries.

    Question: anyone know if Ebf2 interacts with Swi/Snf, as Ebf1 does? Just curious.

  • Tony Kelly says:

    Some people take ice baths and cold showers to (try to)activate brown fat and boost the metabolism. … (others try) exercise and intermittent fasting … (to) convert WAT to BAT.

  • detoxify says:

    This is a smart blog.

  • Ehsan Ali says:

    Great source of information!Extremely interesting article given the increase prevalence of obesity.

  • Jean says:

    Does the thyroid also come into play? I know it touches on weight as well as temperature regulation. Could it be a contributing factor in the balance between white and brown?

  • poul says:

    obesity is the main problem nowadays. And Dr. Francis Collins your all articles are wonderful and interesting.

  • Aravindan says:

    Very excellent article. Only now do I realize that this many types of fats are in us.

  • George says:

    One meal, with a soda, can stack up to be over 1,500 calories. That’s just about the daily limit for the day and it may not even fill you up for long.

  • Bea Cherry says:

    This is very interesting post indeed! If I understand this correctly, brown fat is the good fat. So does that mean we need more of it in our body in order to get the benefits from it?

  • Tamara says:

    Wondering if the reduction of brown fat over years or, its reverse, building up brown fat, can help regulate body temperature in the aging population? This would seem useful for older people that struggle to stay warm. Interesting long term applications….

  • Kel says:

    I would be interested in how they are going to go forward with their research. Is the next step human studies or do they go onto other mammals? I guess it will be a long time before we get any firm findings, but I would definitely love to hear more about it. Although I do think that obesity and heart disease can be controlled by healthier eating in general.

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