Saturday, July 17, 2010

Subcutaneous versus visceral fat: How to tell the difference?

The photos below, from Wikipedia, show two patterns of abdominal fat deposition. The one on the left is predominantly of subcutaneous abdominal fat deposition. The one on the right is an example of visceral abdominal fat deposition, around internal organs, together with a significant amount of subcutaneous fat deposition as well.


Body fat is not an inert mass used only to store energy. Body fat can be seen as a “distributed organ”, as it secretes a number of hormones into the bloodstream. For example, it secretes leptin, which regulates hunger. It secretes adiponectin, which has many health-promoting properties. It also secretes tumor necrosis factor-alpha (more recently referred to as simply “tumor necrosis factor” in the medical literature), which promotes inflammation. Inflammation is necessary to repair damaged tissue and deal with pathogens, but too much of it does more harm than good.

How does one differentiate subcutaneous from visceral abdominal fat?

Subcutaneous abdominal fat shifts position more easily as one’s body moves. When one is standing, subcutaneous fat often tends to fold around the navel, creating a “mouth” shape. Subcutaneous fat is easier to hold in one’s hand, as shown on the left photo above. Because subcutaneous fat tends to “shift” more easily as one changes the position of the body, if you measure your waist circumference lying down and standing up, and the difference is large (a one-inch difference can be considered large), you probably have a significant amount of subcutaneous fat.

Waist circumference is a variable that reflects individual changes in body fat percentage fairly well. This is especially true as one becomes lean (e.g., around 14-17 percent or less of body fat for men, and 21-24 for women), because as that happens abdominal fat contributes to an increasingly higher proportion of total body fat. For people who are lean, a 1-inch reduction in waist circumference will frequently translate into a 2-3 percent reduction in body fat percentage. Having said that, waist circumference comparisons between individuals are often misleading. Waist-to-fat ratios tend to vary a lot among different individuals (like almost any trait). This means that someone with a 34-inch waist (measured at the navel) may have a lower body fat percentage than someone with a 33-inch waist.

Subcutaneous abdominal fat is hard to mobilize; that is, it is hard to burn through diet and exercise. This is why it is often called the “stubborn” abdominal fat. One reason for the difficulty in mobilizing subcutaneous abdominal fat is that the network of blood vessels is not as dense in the area where this type of fat occurs, as it is with visceral fat. Another reason, which is related to degree of vascularization, is that subcutaneous fat is farther away from the portal vein than visceral fat. As such, it has to travel a longer distance to reach the main “highway” that will take it to other tissues (e.g., muscle) for use as energy.

In terms of health, excess subcutaneous fat is not nearly as detrimental as excess visceral fat. Excess visceral fat typically happens together with excess subcutaneous fat; but not necessarily the other way around. For instance, sumo wrestlers frequently have excess subcutaneous fat, but little or no visceral fat. The more health-detrimental effect of excess visceral fat is probably related to its proximity to the portal vein, which amplifies the negative health effects of excessive pro-inflammatory hormone secretion. Those hormones reach a major transport “highway” rather quickly.

Even though excess subcutaneous body fat is more benign than excess visceral fat, excess body fat of any kind is unlikely to be health-promoting. From an evolutionary perspective, excess body fat impaired agile movement and decreased circulating adiponectin levels; the latter leading to a host of negative health effects. In modern humans, negative health effects may be much less pronounced with subcutaneous than visceral fat, but they will still occur.

Based on studies of isolated hunger-gatherers, it is reasonable to estimate “natural” body fat levels among our Stone Age ancestors, and thus optimal body fat levels in modern humans, to be around 6-13 percent in men and 14–20 percent in women.

If you think that being overweight probably protected some of our Stone Age ancestors during times of famine, here is one interesting factoid to consider. It will take over a month for a man weighing 150 lbs and with 10 percent body fat to die from starvation, and death will not be typically caused by too little body fat being left for use as a source of energy. In starvation, normally death will be caused by heart failure, as the body slowly breaks down muscle tissue (including heart muscle) to maintain blood glucose levels.

References:

Arner, P. (2005). Site differences in human subcutaneous adipose tissue metabolism in obesity. Aesthetic Plastic Surgery, 8(1), 13-17.

Brooks, G.A., Fahey, T.D., & Baldwin, K.M. (2005). Exercise physiology: Human bioenergetics and its applications. Boston, MA: McGraw-Hill.

Fleck, S.J., & Kraemer, W.J. (2004). Designing resistance training programs. Champaign, IL: Human Kinetics.

Taubes, G. (2007). Good calories, bad calories: Challenging the conventional wisdom on diet, weight control, and disease. New York, NY: Alfred A. Knopf.

23 comments:

LeonRover said...

Waist Fat relations are probably not easy to survey and extract some meanings from without some other factor being taken into account. Waist Height ratio (WHR) is often referred to in the literature as an anthropomorphic relation with health implications - greater than 50 % is apparently not good.

It is easy to construct one's own Delta Weight/Delta Waist Circumference based on changes in weight and waist circumference to predict how much extra fat weight one may lose if one's waist contracts.

In addition, I have used the Navy Calculation for Fat % based on waist diameter, weight and neck diameter. It is useful for estimating progress. Tanitas are a pain in the podex, particularly now with their age-related and water % internal equations. As far as I can see the split between muscle and fat is still based on measurements from a few bodies from the New York morgue in the early 1900's. ( Which brings me to another pet peeve: one never sees Standard Error of Estimates quoted on physiological measures when regression equation are used. McArdle, Katch, Katch is particularly bad!)

There is also to my knowledge a bunch of studies in relation to visceral fat which use Diameters rather rather than Circumferences for evaluation utilizing an elliptical model for their basis rather than a circular one.

Mark said...

Another great post, Ned.

I wonder how genetics plays a role in this. I'm fairly athletic (about 11% bodyfat), but I still have a paunch. Always have. But I've known fellow athletes with 11% bodyfat and have washboard stomachs. It's strange. And they eat worse than I do!

Did some people evolve to carry fat differently due to different metabolic profiles?

Ned Kock said...

Hi Leon.

Yes, additional measures help get a precise number. Among them are height, neck circumference, and weight. The bioelectrical impedance scales seem to often overestimate body fat percentage.

Waist circumference is arguably one of the best to gauge relatively losses in body fat. That is, if one goes from 33 to 32 1/2 in, that is a good amount of body fat loss (possibly 1.5 lbs in a 150-lb person). Even though it is hard to tell what body fat percentage exactly that person has.

Waist circumference measurement is much better than getting on a scale, as far as body fat loss is concerned.

Ned Kock said...

Hi Mark.

Body fat distribution is highly heritable. I once heard a doctor say that he could tell who belonged to a family and who didn't based on body fat distribution alone.

Our body seems to hold on to certain body fat points more stubbornly. The lean with a paunch one, usually at the lower abdominal area, is a particularly stubborn one.

Interestingly, cortisol mobilizes subcutaneous fat, shifting it to visceral areas. Epinephrine (adrenaline), norepinephrine, and growth hormone than use up the visceral fat. So it seems that what is really needed is the right combination of hormones, at the right times.

There are quick-fix methods out there to purportedly get right of the paunch, but I don't think they last. Often they rely on very unnatural diets (e.g., loads of protein shakes).

Whatever the solution is, it has to be something that will be sustainable. And to be sustainable, most likely it will be based on a whole-foods, natural diet. Ideally we'll look like the folks on this post, effortlessly:

http://healthcorrelator.blogspot.com/2010/05/intermittent-fasting-as-form-of.html

Ned Kock said...

Hi Mark.

Regarding your question related to evolution, I am pretty sure that it has something to do with it, but in the short-term only.

What I mean is that I think some people's adipocytes (body fat cells) have higher insulin sensitivity due to inherited metabolic processes that protected their ancestors against the ravages of short-term events.

For instance, the higher insulin sensitivity might have been selected because their ancestors had to survive one or more grueling trips, with various periods of short-term (a week) unavailability to certain types of food.

Of course the above doesn't mean that having a paunch is healthy in the long run. Degenerative diseases typically happen in the long run. The above means that those unlucky folks who have stubborn ab fat will have a harder time losing it. (Unlucky today; their ancestors were the lucky ones.)

Mark said...

Hi Ned,

That is an interesting theory. Perhaps class played a role. My ancestors were poor Central Europeans. Perhaps their bodies were highly insulin sensitive in order to adapt to short-term food shortages?

I think you absolutely right that insulin sensitivity plays a role. Breakfasts of bacon and eggs give me energy and keep my waist slim. An enormous bowl of Kashi cereal several days per week causes *immediate* fat gain in my waist area. The difference is amazing. (Of course, my doctor told me that I was going to kill myself by eating bacon and eggs...)

Kindke said...

I can confirm from personal experience SC fat is extremely resistent.

All I had to do to loose the VF was go on a ketogenic diet (less than 20g carb per day ), 1 month and its all gone.

The worst parts are reportedly the alpha 2 adrenergic areas, the area just below your belly button and in particular those 2 lobes on the sides of your lower back.

I tried yohimbine and had success but this stuff is pretty heavy on your central nervous system aswell as being banned in the UK.

Kindke said...

To touch on the insulin sensitivity subject, I found this study recently.

http://www.ncbi.nlm.nih.gov/pubmed/15231997

This study for me was quite a revelation, as you can see if you look at the ghrelin graph, lean people get a massive increase during sleeping hours where as obese people dont.

What was interesting also is that for breakfast and lunch, obese people and lean people had similiar ghrelin traits, however at dinner something goes wrong, lean people display a predictable effect on ghrelin but for obese people ghrelin is acting strangly.

I believe this has something to do with insulin sensitivity, the test meals were all quite high carb, and im guessing by dinner time the obese people are insulin resistent while the lean people are still insulin sensitive.

I think this may explain the failure in obese people. Going to bed in an insulin resistant state blunts the nightly ghrelin hormone surge. Ghrelin is a major instigator of lipolysis, and it seems that lean people are always in a higher state of fat burning than obese people as noted by average higher ghrelin levels and the nightly spike.

Ive recently begun experimenting going to bed in an insulin sensitive state by making my last meal in the day at 2pm.

Ned Kock said...

Hi Mark.

Certainly bacon and eggs are much healthier than cereal. But bear in mind that protein also leads to an insulin response, although not in the same order of magnitude as carbs:

http://healthcorrelator.blogspot.com/2010/04/insulin-responses-to-foods-rich-in.html

Eating low carb will set most people's body fat points lower than they were before. Then, when the ad subcutaneous fat persists, it becomes very much a calorie game. Dietary fat is the most calorie-dense food, and dietary fat easily gets stored in adipose tissue.

Insulin in response to protein will prevent stored fat from being released (lipolysis). Eventually eggs and bacon, too much of it, may become a bit of a problem. The solution may be to reduce the total amount of fat in meals, even if keeping the protein content intact. Not too much, because the body eventually compensates:

http://healthcorrelator.blogspot.com/2010/06/compensatory-adaptation-as-unifying.html

The little subcutaneous fat may then disappear. In theory, anyway.

Ned Kock said...

Hi Kindke.

Interesting article that one - "Alterations in the dynamics of circulating ghrelin, adiponectin, and leptin in human obesity."

In addition to the nocturnal difference in ghrelin secretion, the other big difference is in total levels of adiponectin, which I think are big factor in terms of health. To raise adiponectin levels, all one has to do is to lose body fat. The relationship seems to be almost linear, at least in the sample used for this graph:

http://healthcorrelator.blogspot.com/2010/03/adiponectin-supplementation-body-fat.html

Cassandra said...

Ned - What do you make of this research which says that thigh and butt fat are worse:
The more an older woman weighs, the worse her memory, according to new research from Northwestern Medicine. The effect is more pronounced in women who carry excess weight around their hips, known as pear shapes, than women who carry it around their waists, called apple shapes.

Link:http://www.sciencedaily.com/releases/2010/07/100714112832.htm

Ned Kock said...

Hi Cassandra.

The link to the abstract of the study article is here:

http://www3.interscience.wiley.com/journal/123583605/abstract?CRETRY=1&SRETRY=0

Their main conclusions are that:

"Higher BMI was associated with poorer cognitive function in women with smaller WHR."

Translation: In older pear-shaped women, high BMI is associated with poor cognitive function. This makes sense. (Note: WHR = waist-hip ratio.)

"Higher WHR, estimating central fat mass, was associated with higher cognitive function in this cross-sectional study. Further research is needed to clarify the mechanism for this association."

This does not make much sense, especially if we were talking about pre-menopausal women (which is not the case here).

A bit of a red flag here is that their sample size is 8,000+. With that kind of sample size, you can "show" that there is a "significant" association between almost any pair of variables. See this post:

http://healthcorrelator.blogspot.com/2010/07/china-study-with-large-enough-sample.html

So, let me see if I can get the original full-text version of the article. I want to take a look at the strength of the association between WHR and cognitive function.

Ned Kock said...

Hi Cassandra, again.

The full-text of that article doesn't seem that easy to get. I will have to try a bit harder. But I found a couple of others. I am showing the titles and main results below.

Title: "Waist-Hip-Ratio as a Predictor of All-Cause Mortality in High-Functioning Older Adults"

Main results: "... all-cause mortality increased with WHR."

Title: "Total and Regional Adiposity and Cognitive Change in Older Adults: The Health, Aging, and Body Composition study"

Main results: "Higher levels of all adiposity measures were associated with worsening cognitive function in men ... there was no association between adiposity and cognitive change in women.

What these studies above, both with older adults, tell me is that WHR is associated with higher mortality in both men and women, and that body fat is more associated with cognitive impairment in men than in women.

In the least, I would expect something that is causing more death to also impair cognitive ability, but we never know ...

Cassandra said...

Hi Ned --
Thanks for looking into this. I am particularly interested because I'm the traditional "hourglass" and I thought the fact that I carry very little weight in my stomach/waist was good. This study seems to say it's better to be an "apple" regarding cognitive function. I always thought hip/butt/thigh fat was relatively benign, but maybe not.

I do realize it is better to be slimmer altogether and I continue to work on it, sigh.

Ned Kock said...

I haven't gotten the full-text yet, but I have a feeling that the association is very weak Cassandra. Possibly not a real association.

In reading the abstract again, they say that "BMI was inversely related to 3MSE score; for every 1-unit increase in BMI, 3MSE score decreased 0.988 points (P<.001)".

That is, BMI seems to be very strongly associated with their measure of cognitive performance (3MSE). Since BMI is correlated with WHR, when you do a multiple regression analysis linking BMI and WHR to 3MSE, the effect of WHR should essentially disappear.

That is, in a proper test of the effect of BMI on cognitive performance, controlling for WHR, the effect of WHR would be nonsignificant (essentially to low to be taken seriously).

This is probably why they say that further research is needed to clarify their results.

Anonymous said...

I've been reading about wheat belly lately. Not sure if this is just another way of saying carb belly, or if there's something specific about wheat... but,

Is wheat belly, visceral or subcutaneous fat?

Ned Kock said...

A large midsection will be fat, regardless of the food source (refined wheat, table sugar etc.). If it is large (e.g., waist greater than 40 in), it will probably be a combination of VF and SF.

Anonymous said...

Wow since you have mixed evolution theory with science I would not believe any of your text !
How sad that scientist like you are brainwashed !
I am atheist by the way ! but it is a shame read your text
Youssef !

Anonymous said...

when I was younger, thinner, and fitter, all of the methods more or less agreed. However, the last time I calculated it using multiple measurements, such as wrist, neck, height etc it was completely wacky! Apparently, allowing yourself to gain weight and get completely out of shape adds tens of pounds of lean muscle! I don't remember the exact formula I used, as I haven't bothered with them since.

Trina

Anonymous said...

Sorry, my comment above isn't clear - I am calculating lean body mass. I have tried to measure it using scales that measure resistance, and a couple of different calculations using body measurements, plus skin fold measurements. I've never tried the water method.

Trina

Anonymous said...

I have just found out what type of body fat which is visceral fat. Since you seem to know a lot and me researching on my own is just making me more confused I have a few questions.

I am 5'6, 2012lbs, female, my waist is 42 and my hips are 36 or around that. I do not work out often and when I do I ride my bike for 30mins or more.

After keeping a food journal I find that I barely eat 1200 calories daily, and with effort I can get to 1600cal my "maintain amount". This made me google and I heard about starvation mode. At this point I am at a lost as to why I can't drop any of the weight. The amount of calories doesn't seem to be the main reason I am not dropping weight.

After looking up Visceral fat people say to drop down to 1000 calories and to do intense exercises. If I can hardly get hungry enough to get 1200 how is dropping to 1000 going to make a difference?

Different sites say to:
1) Eat high protein
2) Eat low protein
3) Do a full body workout
4) Do intense cardio
5) Focus on strength training
6) Work out for 1:30mins daily

I was tiny when I was younger and look at gaining weight as a good thing since I started to get a figure but I ate noodles, microwave food, and ready to eat food and I ate alot.

This was a semi freakout/ please help. I really just found out about Visceral fat and the first they they mention is how people with this type are prone for heart disease.

Anonymous said...

1:30mins is not what I meant to say 1hour and 30mins sorry.

high cholesterol said...

Our body fat percentage is simply the percentage of fat your body contains.The most accurate way is underwater weighing, but this formula should give you a consistent measurement you can use as a guideline so you can determine if you're losing body fat and/or muscle.