On Visceral Fat and DEXA Scans - Who Can You Trust?
This is a rather long post but I hope you will persevere with the story because I am very interested to hear some other opinions on this subject matter:
Last Thursday I had a DEXA scan which produced the following results: Total Mass (TM): 69.0 kg Fat Mass (FM): 15.63 kg Lean Mass (LM): 50.72 kg Bone Mineral Content (BMC): 2.60 kg Visceral Fat (VAT): 1.03 kg (included in FM) The clinical exercise physiologist (CEP) who did the scan told me the following: "Your visceral fat result of 1.0kg is not good. It should be 0.4kg or less. Ideally it should be zero. I suggest a calorie reduction program to help you lose more weight and I suggest you make an appointment with our registered dietician to get some guidance about this." Eeeeek ….. the very mention of the words ‘registered dietician’ made me want to flee for the front door but I lingered to ask some questions: Q: I have lost more than 25kg of weight in the last 16 months. Do you have any idea what my visceral fat would have been when I was still obese with a body weight of 94 kg? A: I don’t know but for sure it would have been worse. Q: OK but you must have done many of these DEXA scans. What is the worst amount of visceral fat you have ever measured? A: Yes, I have done more than 900 DEXA scans on male subjects and the worst amount of visceral fat I have seen is 4 kg. Q: Is there a safe level of visceral fat? A: No all visceral fat is bad. Q: How much extra weight do you think I need to lose in order to bring my visceral fat below 0.4kg? A: You need to discuss that with the dietician but I also suggest that you come back for repeat scans every 3 months to see if your visceral fat is reducing. The CEP also emailed me my results and added the following: "Regarding your lean mass value, please refer to the following link which shows that someone of your age, sex, height & weight should have at least 49.7-54.0 kgs of lean mass, depending on which formula used (although I prefer The James Formula as it is the most recent). Your lean mass of 50.72 kg is at the lower end of your matched average population range, and therefore this would indicate that you would benefit from a strength/resistance programme to build lean mass, once you have reduced your visceral fat mass." LBM Calculator All of this was a little bit disheartening because in fact I have already been following a strength/resistance program ever since I commenced low carb so I decided to do some research and analysis. The fist thing I realized is that the CEP’s comparison of the DEXA lean mass (LM) result (50.72kg) with the lean body mass (LBM) estimates from the calculator.net weblink is wrong. All of the LBM formulae are based on LBM being equal to Total Body Mass minus Fat Mass, such that TM = FM + LBM The DEXA scan separately measures bone mineral content , such that TM = FM + LM + BMC Checking: 15.63 + 50.72 + 2.60 = 68.95 Hence LBM must include bone mass and therefore it should be compared with the sum of the DEXA lean mass and bone mass results and not just the LM by itself. In my case LM + BMC = 53.3 kg The LBM formulae from the calculator.net weblink give the following estimates: Boer formula: 53.5 kg James formula: 54.1 kg Hume formula: 49.8 kg My research lead me to discover the following: The Hume formula is the oldest correlation (1966) and should not be used at all. The Boer formula should actually be referred to as the Hume & Weyers formula and dates from 1971 The James formula is not the most recent and badly underestimates LBM for overweight and obese subjects. The most recent formula is one, which is not included in the calculator.net weblink. It is the Janmahasation formula dating from 2005 and is considered an improvement of the Hume & Weyers formula. For my height and weight it produces a LBM estimate of 53.2 kg – remarkably close to the DEXA result for LM + BMC of 53.3 kg. So I am feeling less concerned that I have to do something about my ‘apparently’ low lean mass. But what about that pesky visceral fat (1 kg of it) which the CEP says I need to lose before attempting to build extra lean mass? Well my research revealed the following: 1) There appears to be no data to determine what is a 'safe level' of visceral fat but plenty of commentary saying that any amount is bad. 2) I found one highly interesting and useful paper, https://www.researchgate.net/public...ota l_fat_mass which indicates that there is an allometric relationship between visceral fat and total fat mass. After this I found that by combining the allometric relationship between visceral fat and total fat mass together with estimates of fat mass from the Janmahasation LBM formula I was able to extrapolate upwards and downwards from my current weight and deduce the following: 1) A person my height would have to weigh around 112 kg with a BMI of ~40 in order to have around 4kg of visceral fat (i.e. the maximum which the DEXA scan physiologist says she has ever come across). 2) When I started low carb and my weight was 94 kg my visceral fat was probably around 2.6 kg. 3) Extrapolating in the direction of lower weight shows that I would need to achieve a total body weight of around 55kg or less in order for visceral fat to be reduced to 400g or less. Even if I got down to around 63 kg (my weight when I was a distance runner some 30 years ago) the visceral fat level would still be 0.8kg. Therefore my final conclusion is that the DEXA scan physiologist is suggesting a visceral fat target which is impossible but I guess it is good for business if people believe it and keep coming back for scans to check their 'progress'. Should I nonetheless be concerned about having 1 kg of visceral fat? Well I’m not sure but I do wonder how much of it might actually be necessary fat. I understand that organs like the kidneys naturally sit in a layer of fatty tissue called the adipose capsule/perinephric fat. I have no idea what mass this might represent but I rather suspect that some of what the DEXA scan measures as apparently ‘nasty visceral’ fat is probably just this essential perinephric fat. |
It's one risk factor. How's your blood pressure? Blood glucose? Liver fat, and liver enzymes?
https://www.sciencedaily.com/releas...90824151304.htm Quote:
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Thanks for the article. Blood pressure 105/70 Fasting BG: 86 mg/dL Liver function tests all in normal range though I haven't figured out what each of them means: AST 14 U/L ALT 17 U/L Alk Phos 42 U/L Gamma GT 17 U/L T Bilibrubin 13 umol/L T Protein 64 g/L Albumin 38 g/L Globulin 26 g/L |
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I think this conclusion is the most likely. The CEP has a horse in this race, and that is to sign you up to a nutritional and resistance program based on the DEXA results. Both were recommended. Move more, eat less, and get subsequent scans (every 3 months) to track progress. Definitely good for business. Quote:
This is the key. Had you some data from a previous scan before you began losing weight, you would have been able to measure progress, but I think your calculations are fairly close in terms of the amount of visceral fat you had before your weight loss and the amount you have today. I strongly believe people need to have a certain amount of visceral fat for protection of organs. How much is the optimum is the real question and unlikely to be answered accurately by the CEP. Significantly reducing; although, not eliminating, visceral fat is the real sign of progress here. Thanks for the long post. You have done the real research here in your N=1 experience. Very informative information that I believe can be used to better understand the accuracy of DEXA scans and to ensure that the Janmahasation formula is applied to get the most dependable results. One can speculate about why the clinic offering the DEXA scan and interpretation of results uses a different formula. |
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Sounds like you have a risk factor for metabolic syndrome, but not the thing itself. |
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Sorry I don't understand what you mean. |
If it's true that having visceral fat mass of > 0 is a risk factor for metabolic syndrome, then you have A risk factor. But since you are negative on all other measured risk factors, you do not have the disease itself.
A similar example. I have a grandmother, two aunts, a sister and a cousin who have had breast cancer. I have a strong family history, thence, strong risk factors for breast cancer. But I, myself have not had it. And, the older I get, the less likely I am to get it: ALL of them had their first symptoms before the age of 50. You have neatly eliminated all but one of the risk factors for metabolic syndrome. And that one is a guess. MY guess is that it's about as accurate as assuming that total cholesterol greater than 200 is a risk factor for cardiovascular disease, and should be aggressively treated with statins. IOW: totally inaccurate, and based on further totally inaccurate assumptions about fat, in general. |
Thanks MickiSue. I like the cholesterol analogy.
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I was just looking at your weight loss graphs and they look just like mine. Clearly the advice to get help from a registered dietician (or registered dogmatist, as I call them) would increase your fat levels. Quote:
Also, isn't water weight included in the lean mass calculation? LCHF diets are more dehydrating than the average person's, so it is normal to carry less water weight than the average, carb eating person that his targets are based on. If you drank a bottle of water right before the test, you might have achieved the magical 52kg mid-range LBM target. I find this thread very fascinating. I had my LBM determined before and after my LC diet to normal weight via immersion tank. It was 48.4kg before and 46.6kg after losing 28kg. A friend the same age, sex & height had a LBM of 42.9kg. So a 3.7 kg difference in LBM, likely due to my larger frame size. If you think the LBM calculators for men vary a lot, you should see the ones for women. The one that best approximates my LBM involves height, weight, waist, hip, wrist, neck. |
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Bintang, for comparison I'll post my last readings (Aug this year) they also have the current standard range (USA) listed. There's some math in the units measured but looking quickly I think you're liver looks better than mine (mine was in ROUGH shape before, it still is corse according to the echo-texture unfortunately) |
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As for the 0.4kg threshold I’ve continued searching around for info since starting this thread and the only thing I have managed to find so far is the following statement from a health writer's blog: "How Much Visceral Fat can I have before it causes health problems? Research has demonstrated that when we look across the population and stuff everyone under the bell curve, a visceral fat area ranging from 10 to 100 cm2 is considered normal and at around 100 cm2 the risk for heart and metabolic problems begins to increase." http://www.drbillsukala.com.au/heal...-should-i-have/ This is interesting but like so many blog statements it is not backed up by any references/citations. Also it refers to a threshold measure of visceral fat in terms of area (i.e. square centimeters, cm2). My DEXA scan results for visceral fat are reported in volume (cubic centimeters, cm3) and mass (kg). I have no idea how to relate the blogist’s threshold of 100cm2 to my DEXA result. However, at least this information supports the notion that there is a threshold, which IS NOT zero. |
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18 months ago my readings (from a lab in Indonesia) were not looking good either. The results I posted were measured just 10 days ago (from a lab in Australia). I have to say though that the reference ranges for these tests are confusing as they differ from country to country and maybe from lab to lab. |
Yes, and which ones are important and which ones not so much are dependent on what you're looking for :)
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YES. If you are concerned about liver disease, you are looking for entirely different answers than if you are looking for evidence of heart attack. I've been out of the clinical area long enough that I'd have to look up which is which, and I'm not that ambitious right now! |
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Researchers have indeed identified a critical level of visceral adipose tissue (VAT) above which metabolic disturbances are likely to be found. This threshold is 100 to 130 cm2 [Ref 1] with the lower value probably more pertinent to Asian populations - especially Japanese. The threshold is stated as an area because most investigators use a single cross-sectional image as a representative measure of VAT volume and a compromise between accuracy and cost in their research [Ref 2]. However, VAT volume can be estimated from VAT area using correlations (eg. the following charts) from which it can be deduced that 100 to 130 cm2 of threshold VAT area must correspond to a threshold VAT volume of around 2.4 to 3.0 liters, which is ~2.3 to 2.8 kg of VAT mass. Now to another question. How much visceral fat (if any) do young, healthy people have? For some insight here is some data from Sweden [Ref 3]: In the male group, with an age range of 14 to 66 years, the lowest measured VAT area was 14.6 cm2. This would correspond to a VAT volume of around 0.5 liter or a VAT mass of around 0.46 kg. My DEXA scan visceral fat volume result of 1.09 liter (i.e. 1.03kg mass ) corresponds to a VAT area of only 41 cm2, which is way under the critical VAT threshold. At this point I have to conclude that my visceral fat level poses no risk and is more likely the kind of level that one would expect to see in a healthy person at least half my age. So much for the advice of the DEXA scan physiologist. :bash: And good luck to anyone my age who tries to follow her advice and reduce their visceral fat to below 0.4kg. :lol: REFERENCES: [1] Effects of diet and physical activity on adiposity and body fat distribution: implications for the prevention of cardiovascular disease. https://www.ncbi.nlm.nih.gov/pubmed/19094306 [2] Visceral adipose tissue: relations between single-slice areas and total volume https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2040041/ [3] Practical approach for estimation of subcutaneous and visceral adipose tissue http://www.medsci.uu.se/digitalAsse..._112-joel-1.pdf |
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