Visceral Fat Evaluation and

Clinical Significance
Thomas L. Kelly, Senior Principal Scientist
Hologic, Inc.

Introduction including medical costs and indirect costs such as disability,

Obesity is widely recognized as America’s most serious loss of work, and premature death from diabetes.2
public health problem following a Center for Disease Control There is mounting evidence that the distribution and
(CDC) report that 78 million adults (37.5%) and 12.5 million type of excess fat may be an important prognostic indicator
children (17%) are obese.1 For the first time in recorded for disease risk. Unlike subcutaneous fat whose main function
history, obesity threatens to reduce life expectancy from both is energy storage, visceral fat cells are metabolically active and
chronic and acute diseases including cardiovascular disease, impact a wide variety of clinical risk factors including fasting
stroke, dyslipidemia, cancer, hypertension, and diabetes. The glucose levels, serum triglycerides, and cholesterol.3, 4
secular trend of increasing obesity across all age groups has led Visceral fat occurs within the envelope formed by the
to an increased focus on the diagnosis and management of abdominal muscles, principally within the greater and lesser
obesity and obesity-related health risks (see Figure 1).1 omentum that connects the abdominal organs, and in
mesenteric fat. A small amount is also found retroperitoneally.5
Visceral fat is more dangerous than subcutaneous fat
50 Age in years: 20 and over 20–39 40–59 60 and over because visceral fat cells release proteins that contribute to
42.3 inflammation, atherosclerosis, dyslipidemia, and hypertension.
39.7
40
35.7 36.6 37.6 36.6
35.8 36.0
Visceral fat is associated with metabolic risk factors and
35.5
32.6 33.2
31.9
all-cause mortality in men6, and is therefore considered a
30 pathogenic fat depot.7
Percent

20

10

0
All1 Men Women2

Figure 1. Prevalence of obesity among adults aged 20 and over, by sex and age:
United States, 2009-2010

The explosion of type 2 diabetes over the past decade is

perhaps the most serious consequence of the current obesity
epidemic. Nearly 2 million adult Americans were diagnosed
with diabetes in 2010 alone, and the CDC estimates that 79
million Americans are pre-diabetic. Diabetes is the leading
cause of kidney disease, a major cause of heart disease and
stroke and the seventh leading cause of death in the United
Figure 2. Computed tomography image of the abdomen at the level of the fourth
States. The financial burden of the disease is staggering; in lumbar vertebrae with visceral cavity outlined in white (top) and visceral fat filled
2007 alone total expenditures amounted to $174 billion in (bottom).8
Methodology
Hologic scientists have recently developed and patented9
a method for measuring visceral fat from a DXA whole body
scan that is highly correlated and linearly related to visceral fat Visceral cavity
measurements by computed tomography.10 This development
allows clinicians and researchers to classify subjects with
excess visceral fat, thereby identifying the population with the Inner abdominal muscle wall
greatest obesity related health risks. Diet, exercise, surgical, and
Subcutaneous fat
pharmaceutical interventions can now be targeted toward high
risk individuals to maximize health benefits.
The main breakthrough in using DXA for the
measurement of visceral fat was the recognition that the
subcutaneous fat ring, inner abdominal muscle wall, and
visceral cavity are all recognizable anatomical features on
Hologic Discovery high resolution DXA whole body images.
Automated software algorithms identify these anatomical Figure 3. Stylized representation of DXA projected image showing anatomical
features at the level of fourth lumbar vertebrae. Using features including subcutaneous fat, abdominal wall, and visceral cavity.
appropriate modeling, the amount of subcutaneous fat in the
abdominal region can be estimated from the subcutaneous
Clinical Management and Interpretation
fat on each side of the abdominal cavity. This estimate of
It is important to recognize that even subjects who are
subcutaneous fat is subtracted from the total abdominal fat in
normal weight and have a Body Mass Index (BMI) < 25 can
the abdominal region to yield visceral fat.
have a significant accumulation of visceral fat, increasing their
DXA visceral fat area measurements obtained with this
risk for cardiovascular disease, diabetes, and other obesity
method were highly correlated (r=0.93) and linearly related to
related health risks. Likewise, some overweight or obese
visceral fat area measured by computed tomography in a study
patients may have relatively low levels of visceral fat, normal
of 272 black and white women.10 The low prediction error
metabolic profiles, and few or no additional risk factors. A
(SEE=16 g/cm2) and strong functional relationship reported
DXA visceral fat measurement may distinguish apparently
in this study indicates that DXA and computed tomography
normal weight subjects with high visceral fat levels and high
measurements of visceral fat are substantially equivalent.
disease risk from metabolically normal subjects with BMI’s in
Subsequently the DXA visceral fat application received FDA
the overweight or obese category.
clearance, an achievement with several practical and technical
Virtually all visceral fat studies in the literature report
advantages since DXA exams are widely available, less costly,
visceral fat in units of area (cm2); only Hologic Discovery
and deliver a small fraction of the radiation dose compared
DXA scanners report visceral fat in its native area format.
with computed tomography. Furthermore existing whole body
exams, e.g. exams utilized in clinical medicine and in research
studies, can be reanalyzed with the new visceral fat application
as it is 100% backward compatible with all modern Hologic
fan beam technology.

Figure 4. Correlation between visceral fat area measured by computed tomography

(CT) and DXA.
Cross-sectional studies have suggested that visceral fat levels to BMI for obesity classification because FMI is a gender
exceeding 100-110 cm2 adversely affects the metabolic specific measurement of excess fat, whereas BMI is a measure
profile in women.11 Pickhardt et al found that a visceral fat of excess weight. Likewise, DXA measurements of visceral fat
area threshold of 70 cm2 yielded a sensitivity, specificity, and more accurately assess health risks compared with non-specific
accuracy of 83.7%, 80.0%, and 81.3%, respectively, for measures because visceral fat is a primary pathogenic fat depot.
metabolic syndrome in women. Visceral fat area performance
was somewhat lower in men using a 125 cm2 threshold.12 References
Nicklas found that a visceral fat area of 106 cm2 was 1.
Ogden CL, Carroll MD, Kit BK, Flegal KM. Prevalence of obesity in
associated with an elevated risk of metabolic coronary heart the United States, 2009–2010. NCHS data brief, no 82. Hyattsville,
MD: National Center for Health Statistics. 2012. http://www.cdc.gov/
disease (CHD) risk factors and a visceral fat area of 163 cm2 nchs/data/databriefs/db82.pdf
was associated with a markedly increased risk in women. 2.
Centers for Disease Control and Prevention. National Diabetes Fact
The study concluded that “these values may prove useful for Sheet: national estimates and general information on diabetes and
defining visceral obesity and for identifying women most likely prediabetes in the United States, 2011. Atlanta, GA: U.S. Department
to benefit from preventative interventions”. 13 of Health and Human Services, Centers for Disease Control and
Prevention, 2011. http://diabetes.niddk.nih.gov/dm/pubs/statistics/#fast
Visceral Fat Diagnostic Thresholds 3.
Bergman, RN et al. Why Visceral Fat is Bad: Mechanisms of the
Diagnostic thresholds for visceral fat are becoming more Metabolic Syndrome. Obesity (2006) 14, 16S–19S; doi: 10.1038/
oby.2006.277
firmly established as further clinical and research experience is 4.
Weltman, A, et al. Impact of abdominal visceral fat, growth hormone,
gained. Data from population based studies such as NHANES
fitness, and insulin on lipids and lipoproteins in older adults.
will supplement the knowledge base with reference values that Metabolism. 2003 Jan;52(1):73-80.
will provide the analytical framework for interpreting DXA 5.
Freedland, ES. Role of a critical visceral adipose tissue threshold
visceral fat measurements. In the interim the available literature (CVATT) in metabolic syndrome: implications for controlling dietary
supports visceral fat thresholds of 100 cm2 for increased risk carbohydrates: a review. Nutrition & Metabolism 2004, 1:12
and 160 cm2 for high risk. 6.
Kuk JL, et al. Visceral fat is an independent predictor of all-cause
mortality in men. Obesity. 2006;14(2):336-41.
7.
Fox CS, et al Abdominal visceral and subcutaneous adipose tissue
Visceral Fat Classification compartments: association with metabolic risk factors in the
Framingham Heart Study. Circulation. 2007 Jul 3;116(1):39-48.
8.
Yoshizumi T, Nakamura T, Yamane M, et al. Abdominal fat:
NORMAL INCREASED HIGH standardized technique for measurement at CT. Radiology
1999;211:283-286.
10 100 160 300 9.
T.L. Kelly, KE Wilson. Estimating visceral fat by dual-energy
Visceral Fat Area (cm2) absorptiometry. Patent # 7,725,153 (U.S.: Hologic, Inc., 2011).
Figure 5. Visceral fat thresholds associated with metabolic risk factors for
coronary heart disease.12, 13 10.
Micklesfield LK, Goedecke JH, Punyanitya M, Wilson KE, Kelly TL.
Dual-energy x-ray performs as well as clinical computed tomography for
the measurement of visceral fat. Obesity. 2012 May;20(5):1109-14.
11.
Brochu M, Tchernof A, Turner AN, Ades PA, Poehlman ET. Is there a
Summary and Conclusion threshold of visceral fat loss that improves the metabolic profile in obese
Recent government health statistics reveal that obesity postmenopausal women? Metabolism. 2003 May;52(5):599-604.
has exploded to epidemic levels. The management of clinical 12.
Pickhardt PJ, Jee Y, O’Connor SD, Del Rio AM. Visceral Adiposity and
obesity and its related health risks is a vexing clinical problem. Hepatic Steatosis at Abdominal CT: Association With the Metabolic
The reliance on antiquated measurements such as BMI, Syndrome. AJR Am J Roentgenol. 2012 May;198(5):1100-7.
scale weight, and waist circumference further compounds 13.
Nicklas, BJ et al. Visceral Adipose Tissue Cutoffs Associated With
the problem, as anthropomorphic measures often do not Metabolic Risk Factors for Coronary Heart Disease in Women.
Diabetes Care 26:1413–1420, 2003
adequately assess obesity related risks. The end result is that 14.
Pou, KM et al. Patterns of Abdominal Fat Distribution. Diabetes Care.
commonly used clinical measures of obesity misclassify 2009 March; 32(3): 481–485.
individuals in terms of visceral adipose tissue and disease risk.14 15.
T.L. Kelly, K.E. Wilson and S.B. Heymsfield, “Dual energy X-Ray
Improvements to traditional measures of obesity are absorptiometry body composition reference values from NHANES,”
needed, and these refinements must be widely available and PLoS One, 4 (2009), e7038.
cost effective. It has been previously argued15 that DXA Fat
Mass Index (FMI; Fat Mass/Ht2) measurements are superior
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