How do fat cells protect you from metabolic risk?

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In his post yesterday, Peter has discussed the counter-intuitive idea that having too little fat, rather than too much, causes many of the metabolic problems of obesity.  Today I thought it would be good to continue on with this theme and to focus on some of the mechanisms that explain this strange relationship.  Let’s begin where Peter ended off:

Currently, the emerging theory of why obesity is associated with metabolic disease risk suggests that it is not the excess amount of fat that results in problems – but rather, it is the inability of the fat tissue (specifically subcutaneous) to expand enough via the development of numerous, healthy adipocytes or fat cells to store all the excess calories being ingested.

Fat tissue is made up of many small fat cells, called adipocytes , each of which stores a single droplet of lipid. When we say that there are problems with having too little fat, we really mean thatthere are problems with having too few adipocytes.  For the purposes of this discussion, the most important categories of adipocytes are subcutaneous (those found just below the skin),visceral (those found inside of the abdominal wall) and intermuscular (between muscles). I’ve taken the figure below from my Master’s thesis, which shows where each of these types of cells can be found within the body.

What’s interesting about these different types of adipocytes is that they differ in their rates of lipolysis  – essentially how rapidly they release fat into the blood stream. 
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Category: Obesity Research | 8 Comments

Not enough, rather than too much fat, causes metabolic problems of obesity

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That’s right – contrary to what many religiously believe, it is the inability to grow more fat during times of energy surpluss, rather than the excess of fat which appears to directly contribute to the metabolic consequence often associated with obesity.

An article in the New Scientist shines some light on this issue;

Obesity kills, everyone knows that. But is it possible that we’ve been looking at the problem in the wrong way? It seems getting fatter may be part of your body’s defense against the worst effects of unhealthy eating, rather than their direct cause.

While the article goes on to discuss some interesting new research, I feel the author misses an opportunity to really challenge the overwhelming dogma that too much fat, per se, is the cause of metabolic consequence of obesity. From my experience, it is much easier to get the point across by investigating the obvious anomalies or outliers to the often thought direct relationship between excess adiposity and disease.

 

Outlier #1: Lack of adipose tissue leads to severe metabolic abnormalities

Individuals who suffer from a condition called lipodystrophy, have little to no fat tissue (they look extremely athletic, with defined musculature) but display many of the metabolic symptoms thought to be exclusive to obese individuals. Lipodystrophy encompasses a heterogeneous group of disorders associated with whole body or partial lack of adipose tissue, which can be inherited (genetic-origin) or acquired. Not only are patients with lipodystrophy at increased metabolic risk, but the severity of metabolic complications observed is closely related to the extent of their fat loss.

Outlier #2: Excessive growth of adipose tissue leads to healthy metabolic profile


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Category: Obesity Research, Peer Reviewed Research | 3 Comments

Going (coco)nuts for re-hydration

Travis’ Note: Today’s guest post comes from Allana Leblanc.  You can find out more about Allana at the bottom of this post.  You can find out how to submit your own Obesity Panacea guest post here.

Over the past year or so, coconut water has hit the ‘main stream’ so to speak. It’s a) everywhere b) the next power food and c) (and most importantly) trendy. Oh so trendy.  I love all things trendy, especially when they are food related and ESPECIALLY when they’re food AND health related.

With this ‘flood’ of popularity, a lot of my friends have recently asked if coconut water was in fact, ‘all it was cracked up to be’. Every time I was asked, I mumbled something incoherent, pretended to check my phone, or flat out ignore them.

Until now. Well really until last Sunday, which happened to be the morning after a ‘welcome back’ gathering to celebrate yet another year of post-secondary education. That was when I could no longer resist the cool, refreshing siren of ‘ultimate hydration’. After a quick trip to my corner store, I sent Travis a message asking if he’d let me write a post about coconut water.  First he tried to convince me to just start my own blog, but with the promise of leaving him alone for the conceivable future, he said yes.  And so, we have a match up

Coconut water vs. tap water:

An all-out battle for satisfaction, hydration and performance.

First up, meet the players.
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Category: Guest Post, nutrition | Tagged , , | Leave a comment

Thesis/Life Update

At the end of last summer I gave a quick update to let people know what Peter and I had been up to in our personal and professional lives in the preceding year, and I thought that this would be a good chance to do the same thing this year.  I don’t want to speak for Peter, so I’ll just focus on myself in this update, and he can give his own update on what he’s up to in a future post.

I got married last summer, so in comparison to that this year has been pleasantly quiet!  I’m now entering the 4th (and hopefully final) year of my PhD, with a goal of defending my thesis at some point in the spring or early summer of next year.  It will be a very busy fall – writing/submitting several papers, TAing, possibly taking a course on undergraduate teaching (I took one course last year and really enjoyed it), and heading to Australia for the International Congress on Physical Activity and Public Health.  That being said, the fact that I am now done data collection will free up a lot of time, and I’m planning to put in some long hours in the next few months.

Data collection = complete!
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Category: Miscellaneous | Comments Off

Fun With Mud Runs!

Travis’ Note: Today’s guest post comes from Allana Leblanc (now our all-time leader with 3 guest posts to her name).  You can find out more about Allana at the bottom of this post.  You can find out how to submit your own Obesity Panacea guest post here.

Image courtesy Kris Guthrie

With another summer coming to an end, I can imagine that either you, or someone you know has completed a race of some kind. It seems like we’re turning into a race nation with various fun runs, triathalons, duathalons, mud runs, and road races happening almost every weekend.  You can often do these races as teams, as a relay, or as a solo expedition and they come in pretty much every possible distance (160 km ultra-marathon perhaps?).

For lack of a better term, the newest trend in racing seems to be “mud runs” (see here for more info) that promise participants exhilaration and mud.  These are races that challenge (willing!) participants to run up ski hills, over/under/around/through trenches of mud and to throw their body into ice baths, electric shocks and flames.  Through a quick Google search I found the mud run, the Spartan Race, the Warrior Dash, the Dirty Dash, the Punisher Adventure Race, the Dirty Donkey Mud Run, the Mud Hero but I’m sure there are many more.
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Category: Guest Post, Miscellaneous, Physical Activity | Tagged | 5 Comments

Everything you ever wanted to know about breast fat but were afraid to ask

Breast anatomy (1. Chest wall; 2. Pectoralis muscles; 3. Lobules; 4. Nipple; 5. Areola; 6. Milk duct; 7. Fatty tissue; 8. Skin) Source

Before I begin, I should admit that the title of this post probably oversells the depth and breadth of the content that follows.  In fact, this post is going to focus exclusively on the one breast-related issue on which I may be considered an expert, and that is the relationship between breast fat and metabolic risk (if it sounds like I’m bragging, I’m not).  I should also assure people that while this post does contain pictures, they are all completely safe for work.

As you can see in the above figure, fat tissue makes up a large proportion of the tissue – often the majority – within the breasts.  And from what I understand, differences in breast size are due primarily to differences in the amount of fat tissue, as opposed to differences in duct or lobule volume.  Similarly, changes in breast size due to weight loss (which can be seen in the photo at the bottom of this post) are due to reductions in the volume of fat within the breast.

Breast fat is a fascinating topic, but before we get to that specific fat depot, we need to briefly review the major types of fat within your body.  If you’ve been following our blog for a few years this issue will be old hat, so feel free to skip to the next section.

All body fat is not created equal

In contrast to what some advertisements might have you believe, the fat in our bodies is not simply sandwiched between other tissues like a layer of butter on a baguette.  Instead, fat is stored within specialized cells called “adipocytes” (hence fat is referred to as “adipose tissue”).  Regardless of your body size, everyone has adipocytes in their body (as Peter has discussed in the past, having too few fat cells is actually much worse than having too many).  When you lose or gain weight you are primarily changing the amount of fat stored in your adipocytes, rather than adding or removing actual fat cells.

The image below is taken from my Master’s thesis, which illustrates the three main adipocyte depots.  The top image is a cross section of an abdomen, while the two bottom images are cross-sections of a pair of thighs.

Key body fat depots

Visceral adipocytes - these adipocytes are found within the abdominal wall and surround the internal organs (e.g. the viscera).

Intermuscular adipocytes – these are the fat cells that are found in between your muscles. The marbling on a steak is fat stored in these intermuscular adipocytes.

Subcutaneous adipocytes – this is the fat that you can pinch directly underneath your skin.  Love handles, breasts, and anything mentioned in the song My Humps fall into this category.

The importance of this distinction is that these 3 fat depots have very different associations with health risk.  Visceral and intermuscular adipocytes are generally very bad places to store body fat.  Research has consistently shown that the more fat you store in these depots, the greater your risk of death and disease.

In contrast subcutaneous fat in the legs and buttocks actually seems to be protective against heath risk.  For example, this paper from my MSc found that people with more subcutaneous fat in their lower body are actually healthier than people with the same body weight but less subcutaneous lower body fat.  Despite being counter-intuitive, this is a very consistent finding (it made up the bulk of Peter’s PhD thesis).  It’s also the reason why an “apple” body shape (e.g. lots of abdominal fat with very little lower body subcutaneous fat) is associated with much more health risk than the “pear shape”, characterized by fat stored mainly in the hips and thighs.

I’ve borrowed the two images below from one of Peter’s slideshare presentations, which nicely summarize the contrasting effects of visceral and subcutaneous fat accumulation.

Image by Peter Janiszewski

Image by Peter Janiszewski

There are a number of reasons why visceral fat stores are so much worse than lower body subcutaneous stores – as they expand visceral adipocytes become insulin resistant and promote inflammation, while also releasing fat into the blood stream where it can do damage to other tissues like the heart and liver.  In contrast, subcutaneous adipocytes in the legs and butt tend to hold onto fat very tightly (hence why they are sometimes viewed as a “problem area” that are so difficult to slim down), which is actually quite beneficial from a health perspective.

For anyone interested in learning more on this topic, I’d recommend this previous post, or Peter’s excellent series on metabolically healthy obesity.

What is the health impact of breast fat?


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Category: Obesity Research, Peer Reviewed Research | Tagged | 2 Comments