Fat Cell

Fat Cell

Meet the adipocyte or fat cell, the first in an occasional series of #excyting cell types. Each cell, marked by the blue nucleus, is loaded with fat droplets stained in green. 

Why we need fat: Adipocytes have three important jobs: they store energy in the form of fat, they secrete hormones and they respond to insulin to meet the immediate energy needs of our bodies. Obese people who carry out these three functions are metabolically healthy and actually have 38% lower mortality risk. If fat is stored elsewhere, it leads to metabolic disease.

Good fat, bad fat, white fat, brown fat: Not all fat cells are equal. While white fat stores energy, brown fat burns energy to produce heat. Babies and hibernating animals use brown fat to keep warm. The brown color comes from being packed with iron-rich mitochondria. In brown fat, these powerhouses are “uncoupled”: they use energy from fat to pump protons across their membrane but the protons run backwards in a wasteful exercise in futility that generates heat.

Fat is plastic: white fat cells can convert to brown fat by a process induced by cold temperatures. This is a good thing: animals with more brown fat are more resistant to diabetes and obesity.

Fat cells are constant: It is generally believed that the number of fat cells is nearly constant, beyond childhood. Rather, it is the size of the cell that changes. When mature, an adipocyte may be 10 or 20 times its original size.

Image: 3T3-L1 derived adipocytes stained for lipid droplets (green) and DNA (blue). Finalist, GE Healthcare cell imaging competition, 2012 ▶ http://goo.gl/hkzBE Inset, colored scanning electron micrograph of a fat cell. Most of the adipocyte’s volume is taken up by a large lipid (fat or oil) droplet. Fat accumulation starts with a few small lipid droplets which coalesce to make one large droplet. Magnification: x10,000 when printed at 10 centimetres wide.  ▶ http://goo.gl/sZ6hp


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78 Responses to Fat Cell

  1. Naoaki Maeda says:

    Why fat cells are so beautiful 🙂

  2. Rajini Rao says:

    Pretty, aren’t they 🙂

  3. Rajini Rao says:

    Marty Bluet , I just looked it up: cellulite is found in ~90% of females and almost never in males O_o

  4. Does brown fat make babies more resistant to cold that adults?  I ran across an article recently that talked about how babies in Scandinavia are often left to nap outside.  http://www.treehugger.com/culture/let-sleeping-babies-lie-chilly-temps-build-tough-nordic-tots.html

  5. Rajini Rao says:

    Shannan Muskopf , yes, that is right. Babies need the protection of a heat generator because they are so small and their surface to volume ratio is high. Brown fat was designed to keep babies warm. That said, those Nordic tots must be tough 🙂

  6. Rajini Rao says:

    But they are still lurking, Shaker Cherukuri , waiting to inflate again 😉

  7. Rajini Rao says:

    I believe you are right, Marty Bluet , although the process can carry risks (as with other surgery and anesthetic procedures).

  8. Good point Rajini Rao

    I can attest that Nordic tots are tough. The outside napping custom is very old and still prevalent.

  9. Rajini Rao says:

    I wonder if it has something to do with sleeping better at lower temperatures? Most people turn down heating at night to a more comfortable level for sleep.

  10. Rajini Rao says:

    The euphemism is love handles Shaker Cherukuri . Hopefully, someone loves them us 🙂

  11. Rajini Rao says:

    Thex Dar , haha..you turned out great so she must have done it right!

  12. Thanks for that link Shannan Muskopf

    My three boys (youngest going on 28) all napped outside even in cold weather when they were small. Difficult to explain to United States parents that we feel no anxiety about this. We want tough, unanxious, self reliant kids. We live in communities where it would not occur to anyone to drive kids 500 meters to school.

  13. Arun Shroff says:

    Rajini Rao “Babies and hibernating animals use brown fat to keep warm.” What about adults (of the non-hibernating kind :)? 

  14. Rajini Rao says:

    Arun Shroff , we have some too! Although not enough to burn off those high calorie food we eat 🙂

    There is research directed at converting white to brown fat.

  15. I heard Finnish people have more brown fat than others do.

  16. Arun Shroff says:

    Rajini Rao Interesting – so people with more brown fat are likely more resistant to cold weather?  I knew someone who could walk around in freezing temperatures with just a T-Shirt on – and not get sick! 

  17. Rajini Rao says:

    David Bennett , there are ethnic/racial differences in adult brown fat. One paper noted differences among Asian children of different ethnicities. Another, more interesting from a scientific point of view, showed correlations between gene variants (alleles) of the uncoupling protein (the one that wastes energy in brown fat) in women of different races. 

  18. Rajini Rao says:

    Arun Shroff , I’m guessing so, but I bet there are other differences as well. I’ll search the literature for more factors. 

    Anyway, theoretically, colds are caused by viruses and not exposure to cold temperatures although that does lower body temp (particularly in the nasal/chest cavities) and allows the rhinovirus to thrive 🙂

  19. Rajini Rao says:

    A swimmer explains the science behind getting used to the cold of the English Channel: http://dailynews.openwaterswimming.com/2012/01/staying-warm-with-brown-fat.html

  20. Arnav Kalra says:

    Awesome post.

    So, excess of fat is riskier for me when compared to a person living in colder climates?

  21. Rajini Rao “.. there are ethnic/racial differences in adult brown fat..” Do you mean in the amount? Or are there different varieties of brown fat?

  22. Rajini Rao says:

    David Bennett , in the amount for sure, but possibly in the genetic variants of the brown fat mitochondria.

    Arnav Kalra , what a tricky question. I think the risk level is determined by the ratio of your white to brown fat, rather than whether you live in cold or warm climate.

  23. Arnav Kalra says:

    I believe that ratio would depend on the temperature. During summers temperatures easily cross 40-45 degrees Celsius so i think my body doesn’t really need those brown cells. However, I’ve observed that my tolerance for cold is much more than my mom’s , my grandmother’s or any other family member.

    I’ve also read somewhere that for the same body weight a Caucasian will have a greater muscle mass when compared to an Asian.

    BTW are you interested in fauja Singh?

  24. Thex Dar 

      I came minus 20˚C in Finland one December to minus 1˚C in London – and London felt colder. I put it down to the damp London air.

  25. Arnav Kalra says:

    Hmm, i should go move to a colder place. North India is too hot and I’m not used to cold. I get skin problems due to exposure to ~0 degree temperature but my body isn’t affected by it. 

  26. Rajini Rao says:

    Arnav Kalra , those fat cells don’t disappear but they shrink or fill with fat. If your body fat changes with the weather, then its the cell size that is changing not the number. 

    Muscle mass is linked to diet and genetics. There are genes that contribute to muscle mass..Se Jin Lee at my University discovered one by following a particularly robust family of body builders whose baby was unusually muscular 🙂 I’ll find the link, quite extraordinary! 

    Most Indian (particularly vegetarians) are pretty skimpy in the muscle department (as in my family) 🙂

  27. Rajini Rao says:

    Joe Dunlavy , are you and your sister particularly lean given your caloric intake?  

  28. Arnav Kalra says:

    Cell type can change too as mentioned above. If i live in a colder area then just living there should reduce my fat considerably (more than exercise). I’d read an article where they studied tribals in Tanzania and Americans.

    Unexpectedly, the amount of calories burnt by all humans is almost same. Most of it goes towards keeping us alive and exercise has a negligible effect on our energy expenditure. Its all related to diet.


  29. Arnav Kalra says:

    Thex Dar yes. Your skin becomes black, rough, shitty in general. Applying a cream helps temporarily.

  30. Rajini Rao says:

    Cool, thanks for the link Arnav Kalra !

    Thex Dar , you would laugh at my family’s response to cold. In fact, I’m too embarrassed to admit what our thermostat setting is 🙂

    On the flip side, we save on energy bills in the summer..use the air conditioning very sparingly. 

  31. Arun Shroff says:

    Rajini Rao Thanks for the link to that article on swimming. Here is a fascinating snippet from it : “….in the April publication of the New England Journal of Medicine.. ….using different experiments, all three groups demonstrated that prolonged exposure to cold resulted in an increase in an adult’s amount of brown fat.”  So that at least seems to prove one hypothesis many are making here.  But if that is indeed true, and if brown fat is healthier than white fat, then clearly this  also implies that regular exposure to cold.. ought to make you healthier!  Does it or am I just jumping to conclusions here? (I am trying to locate  the original research article – but have not found it yet) 

  32. Rajini Rao says:

    Arun Shroff , that does seem like a sound hypothesis! This article is supportive of your idea: http://www.dailymail.co.uk/health/article-2221602/Why-leaving-heating-avoiding-gym-help-lose-weight.html

  33. I am usually the last one to get cold & I love the cold weather. I need my excess fat to burn quicker (85 lbs).

  34. Rajini Rao says:

    Thex Dar , you are quite right. When a fat cell is full up with stored fat, it does divide. In lean times, the cells shrink but don’t die. Here is an short article explaining: http://calorielab.com/news/2006/08/17/fat-cells-never-say-die/

  35. Rajini Rao says:

    Jeff Brown , I do remember that article! One of those pictures was featured in a post (I forget whose) and it got quite controversial with some people saying it was foolhardy and child abuse, and others saying it made the kids stronger. Either way, it sure does look like those young ones are having fun. Brrrrr…..  🙂

  36. Rajini Rao says:

    It was Morgan Abbou ‘s post of children playing in the snow with their swimming gear on: http://goo.gl/crXXu

  37. Rajini Rao says:

    Why do you ask, Daniel Kight ? I’m guessing that you do?

  38. Daniel Kight says:

    I have eight right now racing in houston Tx at the moment

  39. B Spencer says:

    well, now that I understand these growing monsters…I need to destroy them!!

  40. Arun Shroff says:

    Rajini Rao That dailymail article does seem to confirm my initial hunch. Also discovered that research on cold – and its effect on brown fat –  happens to be a hot new area of research on weight loss 🙂  So running  in cold weather may be healthier for you and lead to greater weight loss than running indoors! 

  41. Rajini Rao says:

    Now you’re throwing cold water on my plan to stay warm! 🙂

  42. Rajini Rao says:

    No, it was in response to running in cold weather 🙂

  43. Ian Netto says:

    What a co-incidence. I’m reading this post with a red velvet cupcake (with cream cheese frosting) in hand.

  44. Arun Shroff says:

     I am just giving you the fa(c)ts Rajini Rao 🙂 

  45. Rajini Rao says:

    May the red velvet go to brown fat, Ian Netto 🙂

  46. Ian Netto says:

    Rajini Rao that’s exactly what I keep telling myself!

  47. Eric Hopper says:

    I didn’t know that about brown fat. Interesting!

  48. Rajini Rao says:

    Eric Hopper , it’s the fat between your shoulder blades.

  49. Arun Shroff says:

    Also found the original research article on cold weather’s effect on brown fat  here- http://www.nejm.org/doi/full/10.1056/NEJMoa0808718 

  50. Eric Hopper says:

    Rajini Rao – That’s also really interesting to know. But do fat cells that change their strips migrate?

  51. Jon Hiller says:

    Thanks Rajini Rao now let’s trim some fat in Washington and start funding science and education again!  Oops, I may have opened a can of worms or fat on this post.  I’m going to fry some spam now 🙂

  52. Rajini Rao says:

    Once sequestration starts, the fat will really be in the fire, Jon Hiller . 

  53. Rajini Rao says:

    Eric Hopper , fat cells do migrate but its hard to find information not related to liposuction 🙂 Apparently, people who have had liposuction worry that fat cells simply repopulate those areas, whereas the plastic surgeons say that they don’t relocate. I’ll keep looking. 

  54. Eric Hopper says:

    Rajini Rao – Thanks for doing my research for me! 😉

  55. thanks ,it’s a nice information

  56. Ulf K. says:

    Rajini Rao do you have any information about how big is the effect of transform white fat cells into browns? Is it enough when I feel cold to not wear the pullover and just to freeze more often? Or go swimming?

  57. Eyas ks says:

    i like it more anything do

  58. pinto xavier says:

    whoa!!!: ” ….beyond childhood. Rather, it is the size of the cell that changes. When mature, an adipocyte may be 10 or 20 times its original size.”

  59. Rajini Rao says:

    Ulf K. , here is what I found regarding cold activation of brown fat. First, just having more brown fat is not useful for dissipating energy..the fat cells have to be activated. Most of the time, they sit there quiescent, not metabolically active.

    Second, I was quite surprised by the modest cold exposure required to activate them. One study exposed volunteers to 14oC for one hour and another to 18oC for 3 hours, using water cooled body suits. Skin temperature fell by a couple degrees and most of the volunteers did not shiver (shivering generates heat as well). In both studies, brown fat was activated to break down fats as seen in a number of different ways..most dramatically by PET scans.

    Arun Shroff , do you have anything to add from your readings on cold activation?

  60. Rajini Rao says:

    J. Elliott-Smith , one way to measure adipocyte turnover is by simply analyzing the fat tissue microscopically, and counting cells. This is what was done in older studies on rats: diet was varied (high fat vs. normal), then total fat was analyzed in detail. Sounds tedious, here is one paper showing a significant increase in cell size but modest increases in cell number (poor quality pdf file: http://ajpendo.physiology.org/content/235/3/E279.full.pdf+html)

    Another way is to use metabolic labeling: for example, 14C isotope is used to label cells, either in experimental animals or volunteers. This paper is behind a paywall, so I’ll try to summarize it a bit later: http://www.nature.com/nature/journal/v453/n7196/full/nature06902.html

    Extract from the abstract: “the number of fat cells stays constant in adulthood in lean and obese individuals, even after marked weight loss, indicating that the number of adipocytes is set during childhood and adolescence. To establish the dynamics within the stable population of adipocytes in adults, we have measured adipocyte turnover by analysing the integration of 14C derived from nuclear bomb tests in genomic DNA6. Approximately 10% of fat cells are renewed annually at all adult ages and levels of body mass index. Neither adipocyte death nor generation rate is altered in early onset obesity, suggesting a tight regulation of fat cell number in this condition during adulthood. The high turnover of adipocytes establishes a new therapeutic target for pharmacological intervention in obesity.”

  61. Arun Shroff says:

    Rajini Rao  Not much – except that the NEJM paper found that the cold effect is most marked in younger people (the study had subjects 18 to 32), and also those with a lower BMI.  It appears that a lot more research needs to be done to study the effect in detail. 

  62. Damn, and here I was, hoping to go read a book in the freezer and walk out thin :-p

  63. Thanks for interesting information. Committee written.

  64. Rajini Rao says:

    Justin Flores  Sure, I’ll send you a limited message with an email address. 

  65. Rajini Rao says:

    Now we know: cold temperatures prolong life (in rats, anyway). Darn it! Here is the article linked by Ben C. O. Grimm on the SoG+ Community: http://hplusmagazine.com/2013/02/28/cold-temperature-and-life-span-its-not-about-the-rate-of-living/

  66. is the plasticity also efficient enough in human adults like babies??

  67. Great thread. I’ve been swimming in cold water ever since I heard I can convert my white fat to brown with a dose of cold. One thing I am surprised hasn’t come up (that is not a pun, wait for it) is the new finding that Viagra converts white fat to brown in mice. Not going there. Yet.


  68. Thanks Rajini Rao btw… “When mature, an adipocyte may be 10 or 20 times its original size.”  (“Original”? Do you mean at birth?)

  69. Rajini Rao says:

    Paul T Morrison , thanks for the link. We need volunteers to test out this upstanding hypothesis 🙂

    John Christopher , these fat cells differentiate (follow a developmental path) from precursor cells. Once formed, they can start packing fat.

  70. Chad Haney says:

    Coincidentally I’m imaging some 40g mice to quantitate fat content with MRI.

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