Thursday, August 21, 2014

The Grizzly Truth About Healthy Obesity

While we continue to debatgrizzly-bear_566_600x450e the incidence and physiology of healthy obesity (i.e. adiposity without any evident health problems), there are ample examples of adiposity in the animal kingdom, where the accumulation of vast amounts of fat tissue are entirely compatible with good health.

One of these fascinating example is the grizzly bear, which accumulates enough fat to last all winter without any apparent ill-effects on its health – indeed, the accumulation of fat to a level that would be considered “morbidly obese” in humans in vital to its survival.

Thus, not only is “healthy” obesity possible in mammals, it may also be an important area of study to better understand healthy obesity (or lack of it) in humans.

Insights into healthy obesity comes from a fascinating study by Lynne Nelson and colleagues from Washington State University, in a paper published in Cell Metabolism.

The researchers studied metabolism in four adult female grizzly bears, trained to “voluntarily” allow blood samples to be drawn for this study (for a video on how exactly this was done click here).

Their study shows that as grizzly bears accumulate fat in preparation for hibernation, they become exquisitely insulin sensitive, only to switch to a state of insulin resistance as they enter hibernation. This process reverses as they emerge from hibernation months later.

While the paper describes in detail the metabolic and hormonal pathways involved in this modulation of insulin sensitivity (via PTEN/AKT signaling in adipose tissue, it suggests that it is the ability to maintain insulin sensitivity in the face of increased adipose tissue that allows these animals to remain metabolically healthy.

As readers may recall, this is akin to the finding in humans that healthy obese individuals also display high levels of insulin sensitivity compared to metabolically unhealthy obese individuals, who display the more typical insulin resistance.

While much of this ability to maintain insulin sensitivity in a state of adiposity may be genetic (as in the rare case of humans with PTEN haploinsufficiency) other factors that enhance insulin sensitivity (e.g. regular aerobic exercise) may also help prevent or alleviate the metabolic consequences of excess fat.

Other factors may well include the actual location of the expanded fat depots, with peripheral accumulation of subcutaneous fat being far less likely to cause metabolic problems (and perhaps even protect against) than visceral or ectopic fat.

Now I guess, we need a study to see how well healthy obese humans do in hibernation.

@DrSharma
Edmonton, AB

Hat tip to Susan Jelinski for pointing me to this paper

ResearchBlogging.orgNelson OL, Jansen HT, Galbreath E, Morgenstern K, Gehring JL, Rigano KS, Lee J, Gong J, Shaywitz AJ, Vella CA, Robbins CT, & Corbit KC (2014). Grizzly Bears Exhibit Augmented Insulin Sensitivity while Obese Prior to a Reversible Insulin Resistance during Hibernation. Cell metabolism, 20 (2), 376-82 PMID: 25100064

 

.

VN:F [1.9.22_1171]
Rating: 0.0/10 (0 votes cast)
VN:F [1.9.22_1171]
Rating: +1 (from 1 vote)

2 Responses to “The Grizzly Truth About Healthy Obesity”

  1. Brian Cohen says:

    I like how you are defining obesity by adiposity, not by BMI. I think we are mislabeling people as healthy based on BMI when they actually have high adiposity and risk for metabolic and cardiac disease. I don’t have the data to back it up, but I am guessing that there are more high adiposity people with normal BMI than there are people mislabeled as obese by BMI who happen to have high muscle/adipose ratio (there just aren’t that many body builders out there!).

    I agree wholeheartedly that fat, like real estate, comes down to location. Such a big difference metabolically between visceral and subcutaneous adipose.

    Perhaps I should propose a sabbatical project where I hibernate and allow people to sample my blood?

  2. Valerie X Armstrong says:

    My book “The Survival of the Fattest”/ A Fairy Tale for Fat Kids…involves this very subject. I am so happy to see this being explored. If you would like a copy of my book, I will gladly send you one.

Leave a Comment

In The News

Diabetics in most need of bariatric surgery, university study finds

Oct. 18, 2013 – Ottawa Citizen: "Encouraging more men to consider bariatric surgery is also important, since it's the best treatment and can stop diabetic patients from needing insulin, said Dr. Arya Sharma, chair in obesity research and management at the University of Alberta." Read article

» More news articles...

Publications

  • Subscribe via Email

    Enter your email address:

    Delivered by FeedBurner




  • Arya Mitra Sharma
  • Disclaimer

    Postings on this blog represent the personal views of Dr. Arya M. Sharma. They are not representative of or endorsed by Alberta Health Services or the Weight Wise Program.
  • Archives

     

  • RSS Weighty Matters

  • Click for related posts

  • Disclaimer

    Medical information and privacy
    Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.


  • Meta

  • Obesity Links

  • If you have benefitted from the information on this site, please take a minute to donate to its maintenance.

  • Home | News | KOL | Media | Publications | Trainees | About
    Copyright 2008–2014 Dr. Arya Sharma, All rights reserved.
    Blog Widget by LinkWithin