DEXA Body Composition Scan

The DEXA body scan is the most accurate method to measure body composition and distribution of fat and muscle mass. Read about my scan and learn more about the DEXA body composition scan.

You may have seem TV commercials for the Cenegenics Medical Institute in Boston.

They provide a variety of services from nutrition coaching, metabolism and exercise studies and healthy aging strategies.

One of the services they provide to assess patients physical condition is the Body Composition DEXA Scan.

The DEXA scan is considered the Gold Standard in body composition measurement and is commonly used to measure bone density. Increasingly it is being used to measure body composition.

I received a Body Composition DEXA Scan at Cenegenics Boston as compensation for writing this review.

Cenegenics has offered the DEXA Scan to their clients since 2011 and to the general public since 2015. In 2012 when I first wrote about body composition studies, no one in the Boston area offered the DEXA scan.

Cenegenics Boston provides a single scan for $175, two for $300 and four for $500. If you get a 10 scan package the cost is $99 per scan.

Why get a DEXA Body Composition Scan

The DEXA Scan is performed using a GE Lunar Prodigy Advance. This machine exposes the body to 1/10 the x-ray radiation of a chest x-ray. So the exposure is minimal.

DEXA Body Composition Scan, Cenegenics BostonDEXA Scan gives you the most precise information about your body fat, muscle, and bone composition, and lets you track changes in body composition over time.

Fitness enthusiasts, athletes, and dieters often use body composition scans to get a baseline of where they are now, and to objectively measure their progress.

Scanning every three to six months is a good way to monitor and evaluate your progress.

Some of us need to monitor our bone density or body fat. Athletes want to measure their body fat and muscle composition.

The primary advantage of DEXA Scan over fat estimating devices such as bioimpedance scales, calipers, tape measure, or displacement estimate devices such as hydrostatic dunk tank or Bod Pod is that the DEXA Scan is actually measuring your body fat and giving you precise measurements.

DEXA Scan gives you precise measurements of fat and muscle distribution around your body.

The DEXA Scan scan also shows muscle asymmetries between your left and right sides. These asymmetries throw weight distribution off, cause muscle miscoordination, and create unnatural stresses that lead to injury.

As a true body composition analysis, you can track potentially dangerous visceral fat around your vital organs. This cannot be done with any of the other body composition measurement tools.

You get a better sense of where you are now. And you can track the improvement over time.

For the average amateur runner like me the DEXA Scan can be very helpful.

Getting a DEXA Scan

DEXA scans are available in most major US, Canadian and UK cities. Many large hospitals also offer them to track the bone density of their older patients.

Check here to find the office offering the scan closest to you. Enter your zip or postal code, or use the map.

Check here for how to prepare for your scan and what to expect during your scan.

My DEXA Scan and results

I became interested in body composition several years ago. In 2012 I wrote about the different tests available in a post titled “What’s Your Number?”

You can perform a BMI calculation online or your doctor may provide your BMI at your annual physical. However, the BMI is imprecise and measures body mass, not body composition.

Over the past 15 years, my weight has fluctuated between 175 and 185lbs. When I began running in January of 2003, my weight was 203 on the bathroom scale. In 2014 I trained all year and ran three marathons and my weight dipped to 169lbs briefly.

When I went for my DEXA scan the office scale had me at 188lbs but the DEXA machine had me at 183lbs. I’m also shrinking and am now just under 6′ tall! Between my weight and decreased stature, my BMI was recorded as 25.7. This puts me just into the “overweight” bracket which begins with a BMI of 25.

The DEXA scan gave me the following numbers:

Total Body Mass: 183.7 lbs
Total Tissue: 176.3 lbs
Total Fat: 43.6 lbs
Lean: 132.7 lbs
Bone Mass: 7.3 lbs
Fat Free Mass: 140.1 lbs

Fat Free Mass combines Bone Mass (7.3) and Lean Mass (132.7) to get 140.1 Fat Free pounds.

Currently I am carrying 43.6 lbs of fat on my body. I was shocked to hear that number. That’s almost a bag of cement!

Dividing 43.6 lbs into my Total Tissue Mass (176.3) gives me a body fat composition of 24.7%. Again, this seemed high.

The important part of this analysis is the next part. The DEXA scans measures both Android and Gynoid fat.

Android fat is primarily carried in the belly area while some is also carried in the chest and upper arms.

Android fat is associated with an increased risk of heart disease and diabetes, hormonal imbalances, some cancers, sleep apnea, and more.

Some Android fat is subcutaneous (under the skin) and some is visceral and surrounds our organs.

The subcutaneous fats is what we see in the mirror and which hides our six packs, no matter how hard we work to get them.

Our bodies need some visceral fat for normal body functions. But too much of a good thing can cause the variety of issues mentioned above.

My estimated Visceral Adipose Tissue was estimated at 2.85 lbs. I was told this is the fat under my abs and that it should be about 1 lb! Yikes! This much fat in this area is not a good thing.

Gynoid fat refers to the body fat that forms around the hips, breasts and thighs. For men this type of fat is typically not an issue. We didn’t discuss this type of fat in depth, but the technician did say that my legs have a healthy amount of fat.

Next Steps and Moving Forward

My goal is to get to 175 lbs. That means loosing about 8 lbs from where I am now. Since my total body fat is 43.6 lbs I need to loose about 18% of my body fat to reach this goal.

With age it becomes increasingly difficult to loose weight. It also becomes increasingly easy to gain weight.

I employed some dietary restrictions over the holidays and didn’t gain any weight. I also maintained my light running routine. This put me in a good position to reach my goal.

By paying attention to my refined carbohydrate and alcohol intake and increasing my running, I will be able to get to 175 and maybe beyond.

My next steps are to train like I have a number for The Boston Marathon. I’ve also been eating more fruit and nuts instead of corn chips and guacamole. I will also be more diligent avoiding sugar as I have been a little lax over the holidays.

Each time I think about heading to the fridge for an IPA, I think about that 2.85 lb pad of fat between my abs and my intestines. Do I really want to feed that thing?

Knowledge is Power

You don’t know what you don’t know. Getting a DEXA Scan is a lot like getting a blood work up at your doctor’s. Until the blood work comes back you don’t know what your cholesterol or triglyceride levels are. You don’t know what your A1c or vitamin levels are.

You can’t take action and control of your health until you know whats going on inside.

While a DEXA scan may seem expensive, I would encourage you to go at least once. It’s not just knowing how much you weigh that’s important. It’s important to know where you carry your weight so that you can understand your risks and what to do about it.

Run well my Friends,


Whats your number?

We are constantly hearing about the obesity epidemic in the United States. For a variety of reasons, including genetics and lifestyle, we as a country are getting heavier and less healthy.

From a National perspective the results of this trend are frightening. From a personal perspective they can be tragic.

What is obesity, how do you know if you are obese, and, why worry about it?

What is Obesity?

Obese is a funny sounding word with serious consequences. I think most of us know what obesity looks like, but what is the difference between being overweight and being obese.

Overweight is defined as a body weight that exceeds an average or that exceeds what is generally considered healthy.

Obesity is a complex disorder involving an excessive amount of body fat.

While many of us can subjectively define “overweight” or “obese”, The Centers for Disease Control (CDC) uses the body Mass Index, or BMI, to define overweight and obesity ranges.

The definitions for adults are:

  • An adult who has a BMI between 25 and 29.9 is considered overweight.
  • An adult who has a BMI of 30 or higher is considered obese.

The following table provides an example.

Height Weight Range BMI Considered
5′ 9″ 124 lbs or less Below 18.5 Underweight
125 lbs to 168 lbs 18.5 to 24.9 Healthy weight
169 lbs to 202 lbs 25.0 to 29.9 Overweight
203 lbs or more 30 or higher Obese

The CDC link above will give you for more information on BMI and weight trends in the United States.

Whats your number?

The CDC provides a BMI calculator for adults and one for children and teens at their website. You can use these links to calculate your own BMI.

BMI does not directly measure the amount of fat that your body has. Body Mass Index (BMI) is a number calculated using a person’s weight and height. No other factors are taken into account.

While the BMI is quick and easy to calculate, there are more accurate methods to measure body fat.

The BMI calculation is a good place for you to start, even though it does not take into account your gender, ethnicity, frame size or muscular development. For most of us it is a reasonably accurate measure to start with and can be done at home.

If your BMI calculation shows that you are overweight or obese, speak with your doctor. She may perform other procedures or refer you to a specialist who can perform more precise measurements of your body fat composition.

Methods to determine body fat percentage

Calipers (Anthropometry, or Skin fold Measurements)

Using a caliper, skins folds are measured in 3-7 locations on the body. Sometimes the measurements are taken several times and averaged to get a more accurate number. These numbers are then put into an equation to determine your body fat percentage. Over 3500 equations have been validated for different body types, age, gender, ethnicity etc.

Like the BMI, skin fold measurements are inexpensive to perform. However, their accuracy depends greatly on the skill of the person doing them and the quality and accuracy of the calipers being used.

The Dunk Tank (Hydrodensitometry, or Underwater Weighing)

In this method a person is weighed outside of the tank and then submerged into a tank of water. They are weighed again in the water and their body density is calculated. This process involves total submersion in the water and exhaling to empty the lungs as completely as possible. This is not a comfortable experience for some people. Using standard equations body fat percentage is calculated from these measurements.

Hydrodensitometry is considered one of the “Gold Standards” of body composition hydrodensitometrymeasurement. Done correctly, this method has been shown to be very accurate.

In clinical studies subjects often need to be measured several times and then the results are averaged. There is also the problem of getting all or nearly all air out of the lungs while submerged and keeping the water as still as possible.


The Bod Pod

Bod PodThis is a method that uses air displacement instead of water to measure body composition. You sit inside of the “Bod Pod” for 8-12 minutes and get a variety of measurements. They claim this method is more accurate than the water displacement method.

Bioelectrical Impedance Analysis (BIA)

In this measurement technique a 50kHz current is applied through electrodes attached to the hands and bare feet. Impedance is the measure of the opposition to the passage of a current when a voltage is applied.

Water is a good conductor of current so it has low impedance. Fat tissue contains 10-20% water so it has greater impedance than fat-free mass in the body which can be 70-75% water.

The results of these tests are then put into equations to figure body mass. When combined with height and weight measurements and body type it is possible to calculate the percentage of body fat, fat-free mass, hydration level and other composition values.

Since the volume of water in the body is being measured, dehydration can affect the results. In preparation for the test care must be taken to maintain similar levels of hydration over a series of tests. Higher accuracy is achieved if the test is performed several times. Some clinicians use this test to measure the level of hydration in athletes or the chronically ill.

This is a painless, simple test, that is inexpensive to perform and under controlled conditions it can be quite accurate. When it was originally available commercially in the 80’s this method was considered un-reliable. Over the years, equipment developed for the clinical and medical practices have become highly accurate.

In 1992, Tanita, introduced a scale that not only measures your weight but also has BIA technology built in. This scale will automatically measure your weight and impedance and calculate your body fat percentage. Today they have a variety of models that range from home to professional use and can get quite sophisticated.

Tanita has some useful charts on body fat, BMI and the health risks of excess fat on their website. This link will download the pdf file for you.

Sometimes you can find these machines at health clubs or physical therapy offices. The accuracy of this measurement method and device have been questioned.

Near-Infrared Interactance (NIR)

This test uses a fiber optic probe pressed up against the skin. Various sites on the body can be used but typically the bicep is used. Infrared light from the optic probe penetrates the tissues and bounces back off of the bone.

Studies have shown that optical densities are linearly related to subcutaneous and total body fat. The NIR data is entered into an equation with the person’s height, weight, frame size and level of activity, to estimate the body fat percentage.

As with all tests there are variables that can affect the test such as skin color and hydration levels. The amount of pressure from the probe against the skin can also affect results. This is another simple, fast and inexpensive test but more research may be needed.

Dual Energy X-ray Absorptiometry (DXA)

This is a relatively new technology which can measure total body mineral, fat-free mass and fat tissue mass. DXA is based on research that shows bone mineral content is directly proportional to the amount of photon energy absorbed by the bone being studied. DXA is most widely used to diagnose and monitor osteoporosis.

DEXA,dual x-ray This technique has the subject lay still on a table for 10 to 20 minutes. The scan uses two low-dose x-ray beams of different energy levels to measure the entire body in 0.5 cm intervals. This test method has been used and studied extensively and has the ability to show exactly where fat is distributed on the body. Because of this method’s precision with only one measurement, it is becoming the new “gold standard”.

I had a DXA or DEXA scan performed at the Cenegenics Medical Institute in Boston. To learn more about the scan and my experience, check out this post.

Converting BMI to body fat percentage

These other techniques do measure body fat, but they need to be done by a trained professional, may be expensive and can be hard to find. If you have done one of these other methods then you know how many of your total pounds are fat, you know your number.

If you are like me and have only done a BMI calculation there is one more step that you need to take to determine your body fat percentage and how many pounds of fat you are carrying around. At I found a formula to convert BMI to percentage of fat.



Multiply BMI by 1.2


Multiply your age by 0.23


Add results of steps 1 & 2


Subtract 5.4 from this total


This is your body fat percentage


Multiply BMI by 1.2


Multiply your age by 0.23


Add results of steps 1 & 2


Subtract 16.2 from this total


This is your body fat percentage

As an example I will use my numbers.

I am 6’ 1” and as of this morning I weigh about 173lbs and I am 48 years old. According to the BMI calculators on the CDC’s web site my BMI is 22.8

Step 1 22.8 x 1.2 = 27.36

Step 2 48 x .23 = 11.04

Step 3 27.36 + 11.04 = 38.40

Step 4 38.40 – 16.2 = 22.2%

According to these calculations my body is 22.2% fat and I am carrying 38.406 pounds of fat around with me. That seems like a lot of fat, but my BMI is well within the normal range of 18.5 to 24.9, which is based on population averages

No one is claiming that the BMI is the most accurate method to measure body composition. It also stands to reason that the indexes will shift higher over time as the trend of society to grow heavier continues. But it is free and can be done at home with reasonable accuracy.

The scales that we use to weigh ourselves are the most significant variable. The scale in my bathroom is different from the scale at my gym and different from the scale at my doctor’s office. My doctor’s office scale usually has me 10lbs heavier than my bathroom scale. If I use my doctor’s data I am 183lbs and my BMI becomes 24.1. Using the same calculations from, my body fat percentage goes to 23.76. This is still within the normal range.

I use my bathroom scale as the constant. Whatever it’s inaccuracies; they are the same every day. My doctor uses a clinical tool in his office. You are all familiar with the black and chrome weight and height scale in just about every doctor’s office in America. I have to assume that his equipment is more accurate than mine. To monitor your weight it is a good practice to use the same scale each time.

Looking at my numbers, the BMI seems to correlate fairly accurately to my body fat percentage. Using my bathroom scale, my BMI is 22.8 and my body fat percentage is 22.2%, so the correlation is .97. Using my doctor’s scale my BMI is 24.1 and my body fat percentage is 23.76, or a .98 correlation. This may not be accurate enough for science and engineering, but we’re not trying to land on the Moon. We just need a fairly accurate measure of our body fat. Using the other techniques we can gain greater precision.

Why should you care about your number?

Now that you know the different ways to determine your body fat percentage, now what?

Why should you care and is it really that important?

A 2012 report by the CDC’s National Center for Health Statistics showed that in 2009-2010, 35.7% of all adults 20 years and older were obese. For women 60 years and older the percentage rises to 42.3%. Here is the link to the pdf of the full report.

Obese means a BMI of 30 or higher. If my BMI were 30 my body fat percentage would be 30.84% and I would be carrying around over 56lbs of body fat! That is 13lbs more than my doctor’s scale shows I am currently carrying.

But what does this mean to you? What would a BMI of 30 mean to you? According to the CDC: Research has shown that as weight increases to reach the levels referred to as “overweight” and “obesity,” the risks for the following conditions also increases:

  • Coronary heart disease
  • Type 2 diabetes
  • Cancers (endometrial, breast, and colon)
  • Hypertension (high blood pressure)
  • Dyslipidemia (for example, high total cholesterol or high levels of triglycerides)
  • Stroke
  • Liver and Gallbladder disease
  • Sleep apnea and respiratory problems
  • Osteoarthritis (a degeneration of cartilage and its underlying bone within a joint)
  • Gynecological problems (abnormal menses, infertility)
  • · In 2008, medical costs associated with obesity were estimated at $147 billion; the medical costs for people who are obese were $1,429 higher than those of normal weight.

According to the American Diabetes Association medical costs for a diabetic are 2.3 times the cost of a person without diabetes. Diabetes causes many chronic diseases that are expensive to treat such as: Heart disease and stroke, high blood pressure, blindness, kidney disease, nervous system damage and amputations. In 2007 the total cost for diagnosed diabetes was $174 billion.

80% of people with Type II diabetes are overweight or obese. A CDC study showed that people with a BMI of 40 or higher are 7.37 times more likely to be diagnosed with Type II diabetes than those with a normal range BMI. As your BMI increases beyond the normal range your risks for diabetes also increases.

A major factor in getting Type II diabetes is your weight. Type II diabetes increases your risk of the diseases listed above. Your weight and fitness level are within your control for the most part. By increasing your activity level and making moderate dietary changes you may be able to avoid Type II diabetes and the cascade of diseases that result from this condition.

This is why you should be concerned about obesity and your own levels of fitness and body fat. Genetics does play a role in obesity but for most of us it does not condemn us to a lifetime of obesity and illness. Discovering your BMI or body fat percentage is the first step in taking control of your health and your future.

So, whats your number?