Good Fat is BAT!

Good Fat is BAT!

Beige, Brite, Brown or White: If you thought all fat was white and wobbly, think again. Some fat depots are colored brown because they are rich in mitochondria– powerhouses of energy loaded with iron-containing cytochrome proteins (bottom panel in image). Beige/Brite fat cells are in between white and brown fat. Human infants have stores of this brown adipose tissue (BAT), up to 5% of their body weight, between their shoulder blades and in their neck, colored green in the MRI scan (top image). Hibernating animals stock up on brown fat too. Why? Because brown fat generates heat.

The Heat is On: Our mitochondria are factories that extract energy from food and store it in the form of a proton (Hydrogen ion) gradient across their borders. Like water cascading down a fall turns a turbine to generate electricity, this gradient of protons can run downhill through the ATP synthase, propelling it like a motor to capture energy from food by making a chemical compound called ATP. But if these protons ran downhill without doing any work, their potential energy would be lost as heat. The mitochondria in brown fat do just that. They make an uncoupling protein that short circuits the proton gradient to generate heat instead of ATP. This form of thermogenesis is important to newborns and hibernating animals who can’t use the shiver reflex to give off heat from their muscles.  

Better with BAT: Since brown fat burns calories, more BAT could counter obesity, cardiovascular disease and Type 2 diabetes. But adult humans lose most brown fat during adolescence. Fortunately, new studies show that we do have some, mostly deep inside our neck (lower image). One approach to increasing BAT is exposure to cold! Brrr … if that sounds uncomfortable, stem cells may boost your BAT. Curiously, brown fat cells share a common lineage, not with white fat cells, but with muscle cells. Recent research has revealed the presence of adult stem cells that can be coaxed into active BAT. The hope is to induce these cells to form calorie-burning brown fat in humans. Now that’s a healthier browning than a tan!   

◑ Images and Refs: (1) Evidence for two types of brown adipose tissue in humans.

(2) How brown is brown fat? Depends where you look. Nedergaard and Cannon Nature Medicine 19, 540–541 (2013)


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77 Responses to Good Fat is BAT!

  1. Norman M. says:

    Thanks for the information of BAT.

  2. Rajini Rao says:

    Norman Ma , believe it or not, white adipose tissue is called WAT. I had the urge to write WAT is that BAT? 🙂

  3. U-Ming Lee says:

    I knew it! Since I haven’t fixed my air conditioning, it’s been very warm and this has contributed to slowing down my metabolism which is why I’ve piled on the pounds.

    Overeating has nothing to do with it 😉

  4. DaFreak says:

    But does it taste just as good as the fat in our fatty foods? :p

    I don’t want to give up on fast food even though I am not particularly fond of animal slaughter and the knock on effects on climate. I want to keep eating but without the guilt so they really need to find a way to make it healthy for both me and the environment! 😉 

    So basically, if we can grow meat, couldn’t we just replace the bad fat with the BAT fat? Or would it taste like crap? If it’s related to muscle, I am thinking it might make meat much tougher and give it some properties that we mostly associate with rubber. :p

  5. Cynthia Bush says:

    BATS the truth !!!


  6. Rajini Rao says:

    U-Ming Lee , I read with surprised skepticism that experimental subjects who are in 15-17oC ambient temperature for a couple of hours actually increased their BAT and caloric burning. So get out of those grocery stores where the HFC drinks tempt (yes, I saw your post) and walk around the parking lot instead 🙂

  7. U-Ming Lee says:

    Rajini Rao Well, in these tropical climes, the ambient temperature in the parking lot is higher than in the grocery shop. 🙂

  8. Rajini Rao says:

    Now that’s a question to flummox a vegetarian scientist, Koen De Paus ! Since brown fat has smaller and fewer lipid droplets, I’m guessing it will taste more like muscle than fat as you’ve suggested. Muscles burn calories of course, but the BAT fat does so quietly in the background, when the temperature falls. 

  9. Rajini Rao says:

    Hah, right you are U-Ming Lee . Lucky you, I’ cold here. Unlike Gnotic Pasta I don’t exactly seek out chilly mountains 🙂

  10. Cynthia Bush says:

    I don’t believe it’s a matter of “tasting” the fat, but rather the type used by the body.

  11. Rajini Rao says:

    Did you say I’m fat, Gnotic Pasta ? :O


  12. DaFreak says:

    I guess this gives us all a reason to turn off the heater. Save both energy, money and planet while getting healthier in the process. Win-Win-Win-Win! Although I guess we’d become rather grumpy if we are constantly shivering so there’s a lose in there too. :p

  13. I guess I was quite wrong. I though fat was yellow!

    In fact, a couple of weeks ago there was a documentary on tv about forensic physicians and they showed human fat and it was yellow, if I don’t misremember.

  14. Cynthia Bush says:

    Rajini, now I’m heading for the “brown” ice cream…!

  15. Rajini Rao says:

    Koen De Paus , the beauty of BAT is that it is non-shivering thermogenesis. In other words, the temperature has to be cool but not cold enough to shiver, to activate all that calorie burning. 

  16. Rajini Rao says:

    Víktor Bautista i Roca most adult fat is whitish yellow (the yellow tinge comes from the mitochondria). Pure fat is white. We don’t have much brown fat as adults. 

  17. Cynthia Bush says:

    Viktor, the human fat one sees in surgery is generally yellow. This discussion is really about the often unknown brown fat present in infants & hypothetical uses for it – with a little humor mixed in !!!

  18. Rajini Rao says:

    Gnotic Pasta indeed there is more brown fat in people living in colder climates. Also, when brown fat is measured there are seasonal variations that match the outside temperature. I saw a study that used this to make the point that it was important to take seasons into account when monitoring brown fat in people. 

  19. Rajini Rao says:

    Gnotic Pasta , maybe I will!  From Anouk et al. 2013: “In recent years, it has been shown that humans have active brown adipose tissue (BAT) depots, raising the question of whether activation and recruitment of BAT can be a target to counterbalance the current obesity pandemic. Here, we show that a 10-day cold acclimation protocol in humans increases BAT activity in parallel with an increase in nonshivering thermogenesis (NST). No sex differences in BAT presence and activity were found either before or after cold acclimation. …… The observed physiological acclimation is in line with the subjective changes in temperature sensation; upon cold acclimation, the subjects judged the environment warmer, felt more comfortable in the cold, and reported less shivering. The combined results suggest that a variable indoor environment with frequent cold exposures might be an acceptable and economic manner to increase energy expenditure and may contribute to counteracting the current obesity epidemic.”

    Ref: J Clin Invest. 2013;123(8):3395–3403.

  20. Chad Haney says:

    Nice post Rajini Rao. Maybe I’ll write about the Dixon method which is often used to cancel the fat signal in MRI. Of course some researchers use it to enhance the fat signal. They did a really good job with segmentation. I hope people realize that the image shown is colorized, much like the SEM images that people get excited about. My former boss developed a method to image different types of fat with spectroscopy and not the Dixon method.

  21. Cynthia Bush says:

    Rajini, I have always been curious about the people who can tolerate intensely-cold situations such as climbing K-2.

    Do you have any references for this?

  22. Rajini Rao says:

    Cynthia Bush that’s an interesting question. I’m sure there is metabolic adaptation and some genetic influence on cold tolerance as well. If I find something, I’ll share it here, thanks! 

  23. Rajini Rao says:

    Chad Haney I forget the imaging method they used for BAT..something to do with glucose uptake? Let me check..

  24. Chad Haney says:

    Rajini Rao I skimmed the methods quickly. I think it was the Dixon method for fat suppression in MRI. Let me get a second cuppa and read more carefully.

  25. DaFreak says:

    Thanks for the tip Rajini Rao, I actually just turned down my thermostat by a few degrees to try and find my limit before shivers. 🙂 

  26. Rajini Rao says:

    Great thanks, Chad Haney . The beautiful baby image is from Liddell et al. Nature Medicine 19, 631–634 (2013). The analyis and imaging techinque is what got them into Nature, I believe. 

  27. Chad Haney says:

    A bit sad they are post mortem.

  28. Rajini Rao says:

    Oh, I did not realize they were post mortem, Chad Haney 😦

    But the imaging could be done with live subjects, no? 

  29. Rajini Rao says:

    That’s much too cold for me, Gnotic Pasta . I’m not even going to tell you what our thermostat is set at 😛

  30. Chad Haney says:

    Maybe Rajini Rao, remember my MRI headphone post? That was clever to image sleeping babies.

  31. Cynthia Bush says:

    Gnotic, you must have the counter-current heating system found in birds!!!

  32. Rajini Rao says:

    Yes, I’m blaming everything on my genes 😉 

    Cynthia Bush , our Dan sure is one for the chicks birds! 😀

  33. Cynthia Bush says:

    Wow, Gnotic, I didn’t know you have feathers…that would explain many things ○~))

  34. Chad Haney says:

    He has a flock, I don’t know about feathers.

  35. Clint says:

    Author Tim Ferriss covered this sort of thing in his book ‘The Four Hour Body’ where, from memory, he suggested placing a cold, damp towel across the back of your neck whilst doing sit down tasks, such as writing, working on a computer, watching television that sort of thing. The aim is to keep your temperature down, but not freezing, to help with fat burning. Much along the lines of what’s being discussed here.

    Seems there might well be something in it.

    Wonderful, informative thread, everyone.

  36. Rajini Rao says:

    Clint Fudge thanks for the information on the book. Here’s to staying cool 🙂

  37. Cynthia Bush says:

    As an addendum: I suggest sex for the rest of the day – it definitely burns a few calories…!!! 《♥》

  38. Only problem is how to get more BAT. Last I heard it helps if you live in a cold place… Brrr…

  39. Cynthia Bush

    Just how in shape are you that you can have a day long sex marathon?! 🙂

  40. Cynthia Bush says:

    Reading the Kama Sutra… will let you know •~)

  41. Rajini Rao says:

    fan tai that’s why I suggested stem cell therapy in lieu of the cooler temperatures. Hope we don’t accumulate too much white fat while waiting for the technology to catch up 🙂

  42. Cynthia Bush says:

    Rajini, this has been an informative and fun post!


  43. Rajini Rao says:

    Thanks for helping to make it so, Cynthia Bush . Enjoy the weekend 🙂

  44. Cynthia Bush


    Now, which page are we talking about?

    (Funny how a book on the philosophy of life is now primarily known as a sex manual :))

  45. Thanx 4 very informative post

  46. Excellent post, Rajini Rao! I’ve known about brown fat for years, and wondered about it when lying in bed, sweating, after eating a high-energy dinner too close to bedtime. 

  47. Rajini Rao says:

    I know that feeling David Archer . Why does a good meal leave us so sleepy anyway? 🙂

  48. Chad Haney says:

    Functional hyperemia?

  49. Rajini Rao I’ve always assumed that feeling tired after a heavy meal is the result of blood flow congregating in the hardworking viscera (reducing available energy to voluntary systems); and you’re now fed, so your brain doesn’t need to do anything much so it might as well get out of the way.

    (sub-note: I just learned something un-useful: the singular of viscera is viscus – useless, because no one uses the singular form, and if I do, people will be thinking about fluids and viscosity… hmmm).

  50. Rajini Rao says:

    So both David Archer and Chad Haney suggest that increased blood flow (hyperemia) to the digestive system after a heavy meal would trigger somnolence…because of less blood flow to the brain? 

    Hey, I did not know that the singular of viscera is viscus! Probably because viscera is always used in the plural 🙂

  51. Panah Rad says:

    Very nice presentation 🙂

  52. Jim Gorycki says:

    Rajini Rao thanks. exposure to cold can help burn calories as long as you don ‘t go into shock and / or hypothermia? What about sweating during the summer (avoiding heat stroke) ?

  53. Rajini Rao says:

    Jim Gorycki , that’s right- cold exposure can be mild enough to not trigger shivering, so that is not too bad. Sweating during summer cools us off, so it is an important means of thermoregulation. Brown fat is less active during the summer though. 

  54. Tom Lee says:

    Nice post again Rajini Rao. BAT, FAT and ATP . Please bring more on! 🙂

  55. Jean Liss says:

    Hmmm, I wonder if there is any difference in obesity when corrected to birth date for people growing up in environments that have extremes in temperature.

  56. I just want to point out that while I can get sleepy after a meal, especially if I don’t have enough sleep…

    I haven’t had such issues in the past 2 years due to my standing desk at work. One day, I had to sit down to do some work after lunch… My god the yawns and sleepy eyelids…

  57. Rajini Rao 

    Body temperature seems to be important in other respects. I found this today:

    …”results, just published in the Proceedings of the National Academy of Sciences, revealed that the tumors in the mice caged in the cooler environment showed a typical rapid rate of growth” 

  58. Rajini Rao says:

    John Condliffe temperature is certainly important as that story on cancer growth shows, but understanding the mechanism is complex because our body temperature  (or that of the mice) is likely the same whether is is chilly outside or toasty. After all, we regulate our temperature tightly. But our stress levels must be different and this must indirectly alter our metabolism and immune response. It’s a fascinating finding, thanks for the link. 

  59. Rajini Rao says:

    Jean Liss it would be hard to control for all the differences in lifestyle, diet, etc. but I’m guessing there are some correlations out there between obesity and latitude/temperature. It would be easier to do a study with mice 🙂 A quick check on PubMed found quite a few hits for obesity and temperature, like this one correlating temperature at the time of conception (huh?) and BMI:

    But wait, cold temperature correlates with higher cardiovascular disease…I guess we can’t win?! 🙂

  60. Jean Liss says:

    I was thinking of how the BAT is used early in life (baby born in January may need more heating than one born in April). How would early use (or lack of use) impact obesity later in life. I suppose you would need to look at populations actually exposed to weather. I would think that if the study is large enough, each group would have enough of each lifestyle category. Just a thought…

  61. Rajini Rao says:

    Good point, Jean Liss . One way early environments could have an impact on events later in life could be by epigenetic modifications that alter our gene expression for the long term. 

  62. Rajini Rao I should have said ambient, not body temperature, but it’s your fault, Rajini. My head is spinning with your bats wats, fats,etc – not to mention those bat cats on Wall Street – gave me a dose of semantic hives, just when I was learning how, not wat to write good.

  63. Rajini Rao says:

    John Condliffe , my bad to dwell on a fad that was a tad too mad. 

    I did get that the study was on the effect of ambient temperature. What I was trying to say was that our body temperature is constant despite the ambient temperature. So any biological effect must be the indirect result of ambient temperature, not direct.  

  64. Chad Haney says:

    Tit for tat about BAT and WAT?

  65. There are no winners in the tit-for-tat rat- or bat-race. Just rats or bats.

  66. Cynthia Bush says:

    May I point out in this post with a life of it’s own, that often in assisting couples patients wishing to lose weight that the male will almost always lose more & at a higher rate than the female secondary to the added muscle mass of the male.

    Saves many arguments over who’s doing the “best” job!

  67. Cynthia Bush says:

    P.S. Look at the studies on Eskimos.

  68. Rajini Rao says:

    Cynthia Bush now my curiosity is aroused! Eskimo men lose weight faster than women and does this have something to do with the Arctic temperatures? 🙂

  69. Cynthia Bush says:

    Still believe it goes back to gender-related muscle mass, although the Eskimos have a unique environment as well as lifestyle.

  70. Marta Rauch says:

    Rajini Rao thanks for the interesting post!

  71. Rajini Rao says:

    Glad that you liked it, Marta Rauch 🙂

  72. Marta Rauch says:

    Rajini Rao we always look forward to your engaging posts. You always pick such interesting topics, and you present them so well. 🙂

  73. Rajini Rao says:

    Aleksandr Ivanov it was pointed out in one of the earlier comments that brown fat probably tastes more like muscle than fat 🙂

  74. Einstein was right, again, breaking atoms is easier than changing people’s minds…instead of giving up french fries and moving our body a little bit, we look for a gene or cell therapy…

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