Visceral fat rating - How can I determine how much visceral fat I have?

How to measure visceral fat?

There are three main ways to measure the amount of visceral fat in your body, including diagnostic imaging, bio-electrical impedance, and waist circumference measurements. They various methods all have trade-offs in terms of cost, accuracy, and convenience. The following article briefly examines the cost, accuracy, and convenience of various methods, as well as other trade-offs.

A. MRI / CT scans

Accuracy: Extremely accurate. With proper companion software, MRI's are able to give near exact measurements of visceral fat area
Cost: $199 (at MRI Pathways) to several thousand
Convenience: Low, scanning has to be done at a imaging facility.
Summary: The gold standard of visceral fat measurement in terms of accuracy. MRI's also have no radiation, however cost and convenience can be an issue for many individuals however.

Both Magnetic Resonance Imaging (MRI) and X-ray computed tomography (CT) can directly see and therefore measure the amount of visceral fat inside the body. Several studies have been conducted to determine how to best measure visceral fat using an MRI and / or CT scan¹. Studies of over methods to measure visceral fat use MRI and CT scans as a benchmark to compare their accuracy. Cost is the main issue, but MRI Pathways offers visceral fat screens for $199.

B. Bioelectrcial impedance (BIA)

Accuracy: Varies by machine, but only somewhat accurate, comparable to estimating visceral fat from waist circumference or BMI².
Cost: Devices that can "measure" visceral fat generally cost at least $50 dollars and are most commonly produced by Omron and Tanita.
Convenience: Very convenient, since scanning can be done at home after the purchase of a machine.
Summary: Bioelectrical impedance devices can be useful to roughly estimate if you have a healthy or unhealthy level of visceral fat but should not be used to estimate your exact visceral fat amount.

The first bioelectrical impedance devices used a harmless electrical current to estimate the amount of water in your body and approximate your body fat percentage. More recent devices use electrical currents of different frequencies to estimate the amount of visceral fat³. Some studies, have found accuracy levels similar to those of MRI's, but others have found accuracy levels similar to that of waist circumference measurements. In fact, one study found that "visceral fat" impedance devices were essentially measuring waist size instead of visceral fat. In my personal experience using an Omron device and MRI scanner, Omron visceral fat measurements are up to 30% off. For example, in my most recent comparison, I had ~110 cm^2 of visceral fat at the belly button level and my Omron device (pictured above) estimated ~80 cm^2.

C. Waist-to-hip ratio and waist circumference

Accuracy: Individuals measurements are not very accurate. But high waist-to-hip ratios and large waist circumferences are signs of high levels of visceral fat
Cost: Very low, any tape measurer will do
Convenience: Extremely convenient

Summary: Waist-to-hip ratio and waist circumference are a good method to determine if you have unhealthy levels of visceral fat.

40 year old male with very high levels
of visceral fat and BMI of 25. Fat
appears white on an MRI.

Circumference measurements of the waist and hip are quick, easy, and inexpensive ways to determine if you have unhealthy levels of visceral fat. These tests can be performed by anyone with only a tape measurer. To calculate your waist circumference, place the tape measurer over the belly button parallel to the floor. The hip circumference is measured across the largest protrusion of the buttocks. Visceral fat levels are likely excessive for waist circumference measurements larger than 40 inches for men and 36 inches for women. Similarly, waist to hip ratios higher than 1.0 for men and 0.85 for women are considered dangerous.

References Cited:
1. http://jap.physiology.org/content/97/6/2333.full#ref-list-1
2. http://onlinelibrary.wiley.com/doi/10.1038/oby.2010.71/pdf
3. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2858179/
4. http://weightology.net/weightologyweekly/?page_id=218 
5. http://www.itochu.co.jp/en/news/2011/110822.html

Visceral fat - What is it and why is it bad for me?

I. Visceral fat vs subcutaneous fat?

There are two main types of fat in the body, subcutaneous fat and visceral fat. 

Subcutaneous fat lies directly underneath the skin in a region called the hypodermis.  Since subcutaneous fat lies over the muscle, you can grab and feel subcutaneous fat with your hands. Subcutaneous fat can look unattractive and will reduce muscle definition, but is considered to be mostly harmless from a health perspective.

Visceral fat is the fat that surrounds the organs in the belly and cannot be seen except through the use of an MRI or CT scan. Visceral fat is extremely dangerous from a health perspective and is correlated with a large number of chronic diseases. BMI and waist circumference often serve as indirect measurements of visceral fat, but both only loosely correlate with visceral fat. For example heavier individuals generally have higher levels of visceral fat, but 25% of individuals with a normal BMI (18-25) are considered to be metabolically obese and have unhealthy levels of visceral fat. 

II. What are the health implications of visceral fat?

There has been significant research done over the past 70-80 years correlating visceral fat with an increased risk for stroke, heart attack, and diabetes. Numerous studies have demonstrated that individuals with high levels of visceral fat have high cholesterol, increased blood pressure, and increased insulin resistance. Furthermore, when visceral fat levels are reduced, individuals see significant improvements in their cholesterol, blood pressure, and diabetes leading to major reductions in heart attacks and strokes.

More recent research has also suggested that high levels of visceral fat are correlated to dementia and cancer. A study, by Dr. Whitmer, of 6,500 members of Kaiser Permanente's patients in Northern California, saw that individuals with larger waist size, a rough measurement of visceral fat, had higher risk for dementia than those with smaller waists. Another recent research study done in mice showed that mice who had their visceral fat surgically removed had significantly reduced rates of cancer compared to mice who received a sham surgery.

III. Why might visceral fat be so unhealthy?

The exact details of why visceral fat is so unhealthy are not fully understood, but recent research has demonstrated that visceral fat is extremely metabolically active and secretes large amounts of hormones. These hormones have profound impacts on our health in a variety of ways. 

For example, visceral fat cells secrete significant amounts of cytokines (e.g., interluken 6, tumor necrosis factor) that are similar to hormones released by the immune system. These hormones cause chronic low grade inflammation in our body that may lead to increased insulin resistance and plaque formation. Similarly, visceral fat cells secrete leptin. Too much leptin may cause your body to become desensitized to leptin leading to hindered appetite regulation and difficulties with learning and memory. Visceral fat also suppresses the production of adiponectin, a hormone found to have anti-diabetic, anti-inflammatory, and anti-oncogenic functions.