Tag Archive for: DEXA

Again with the BMI?

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I got an email from a long-time reader about a recently published study comparing BMI calculated from height and weight with percent body fat calculated via Dual Energy X-Ray Absorptiometry commonly called DEXA. The objective of the study was to see if BMI was accurate in predicting the differences between underweight, normal weight, and several degrees of overweight and obesity with measure of body fatness.

Their subject pool was 1,351 Caucasian men and women 18–98 years old. This was a cross-sectional study (and more than likely a retrospective study) of patients in Italy who had their body fat assessed via DEXA between 2013 and 2024. While this paper contained hundreds of numbers, the essence of what they found was that for those with normal-weight BMI, body fatness was accurate, but for underweight and overweight and obese subjects, BMI under or overestimated their actual body fat; in the chart above, a red dot indicates someone whose BMI was misclassified. The authors felt that the World Health Organization should consider more research because the misclassification may impact diagnostic capability and thus lead to unnecessary treatment protocols.

Why BMI Should Still Be Used

I think the researchers are wrong in their conclusion for the following reasons:

  • While there were definite points where people were misclassified based on the graphic presentation of all data points, it was mostly on the margins. Is there a difference between a BMI of 24.5 versus 25.5? Is there a real difference in a person who has a BMI of 33.0 versus 36.0? Because of the way the data were analyzed by weight classification, the measure loses the nuance.
  • Regardless of the numbers, a physical examination by the healthcare professional should confirm whether a person is normal weight or overweight based on the fluffiness factor. People of the same height and weight may look muscular or like the doughboy of commercials.

The Bottom Line

The question of using BMI as a measure of body fatness in large groups will probably never be over. But when assessing large groups of people, it’s still the best measure for an overview of whether a population is underweight, normal weight, or overweight. If people really need to know more, they can always pay to have a DEXA scan done.

On a personal level, will it really give you any more information than when you stand naked in front of a mirror? When you know, you know. The important question is what are you going to do about it?

What are you prepared to do today?

        Dr. Chet

Reference: Nutrients. 2025. https://doi.org/10.3390/ nu17132162

Creatine: Does Size Matter?

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The researchers in Tuesday’s study demonstrated that the use of creatine did not increase muscle size after considering the increase in fluid levels. The major problem is the limited scope of the study: looking only at changes in lean body mass. While the researchers should be given credit for the approach using DEXA, there are several issues with the study.

Age: The researchers used both men and women in the study—no problem if you have enough of each gender. The problem was that they included subjects between 18 and 50 years old; research has shown that muscle loss due to age can begin as early as 40. With only 63 subjects, ideally it would mean 15 men and 15 women in each group. Dividing those few subjects into under 40 and over 40 means as few as six or seven subjects in each group. That’s just not enough subjects to prove their point; it’s sufficient for a pilot study, but not enough to determine health recommendations.

SEM: SEM stands for Standard Error of Measurement. The DEXA scan has limitations in determining the lean body mass with precision. The differences in lean body mass fell within the standard error of the measurement; the measuring tool wasn’t precise enough to measure actual differences.

Strength: Where was the strength data comparing differences in gains between the creatine and experimental group? Looking at lean body mass is looking at a combination of factors, but strength is strength: the amount of weight can you lift in several lifts like the dead lift, the squat, and the bench press. You can’t do such an intensive study and not measure the simplest variable. I’ve emailed the corresponding author, but he’s on a break in Australia. If I get a response, I’ll share it with you.

The Bottom Line

Creatine is a natural substance that may be beneficial for a variety of issues besides muscle growth. I use it every day because I lift to increase strength, but also because it benefits energy levels, skin, muscles, and other organs as well. I think everyone over 40 can probably benefit from taking five grams of creatine monohydrate every day.

Check with your doctor to find out your limitations on exercise intensity and get after it. Weight training should be a part of your regular routine, and creatine is a natural way of making more energy to increase muscular strength.

What are you prepared to do today?

        Dr. Chet

Reference:  https://doi.org/10.3390/nu17061081

Does Creatine Help Build Muscle?

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Creatine is a naturally occurring chemical your body makes by combining glycine, arginine, and methionine. It’s primarily used in energy production as a precursor in the manufacture of ATP in your body. Creatine is often used to help increase muscle mass in people who train with weights and that’s the focus of the paper I’m going to review.

Researchers in Australia recruited male and female subjects who had been sedentary and had not done any form of resistance training or creatine supplementation in the past year. They collected data on 33 controls and 30 experimental subjects for a 13-week creatine supplementation and resistance training study. The objective was to see if there were actual changes in muscle mass and lean body mass within the resistance training and supplementation program. Prior research had shown that creatine may change only water levels—creatine is known to increase fluid levels in muscle.

The tool they used to assess fluid levels was DEXA to scan for lean body mass before the study began, after the 7-day wash-in period with creatine, and after the 13-week resistance training program. They found that lean body mass increased during the wash-in period in the supplementation group before the resistance training program began, and the difference in lean body mass was maintained throughout the resistance training program. In response to the resistance training program, both groups increased lean body mass by 4.4 pounds after accounting for the initial difference in weight. Therefore, they concluded that creatine may not contribute to increases in lean body mass when used in a resistance training program because of the lack of difference between the supplement and the placebo group once the initial lean body mass was accounted for. But did they ask the correct question? We’ll find out on Saturday.

Tomorrow night is the Insider Conference Call. If you want to get your questions answered, become an Insider before 8 p.m. tomorrow night to join in.

What are you prepared to do today?

        Dr. Chet

Reference:  https://doi.org/10.3390/nu17061081

Is Spot Reduction Possible?

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One of the questions that I’ve thought about over the years is what happens to the skeletal muscle and fat mass in non-exercising parts of the body. If you’re a runner or a walker, what happens to your upper body? What happens to your lower body? Do you retain or even increase the muscles in your thighs and calves? Do you lose fat from your legs? How about your upper body? Do you maintain the muscle mass that you had, or do you lose some? What about the fat mass? Lose or gain?

When I was a graduate student, I ran the body composition laboratory. Over my years in the lab, I underwater weighed probably 5,000 people, from five-year-olds to 90-year-olds, from those who were underweight to morbidly obese, from tiny little gymnasts to a Big 10 hockey team. While underwater weighing was the gold standard at the time, it used some assumptions about the distribution of skeletal muscle, bones, and fat mass that weren’t as precise as they should be. These days, state-of-the-art is dual X-ray absorptiometry, which is called DEXA for short. But that doesn’t give us a precise analysis of body composition to answer those questions either.

We now have that technology in magnetic resonance imaging. Using MRI can begin to give us the answer to those questions about muscle and fat mass. Can you get rid of that stubborn belly fat? We finally may have some answers, and I’ll tell you about the latest research on Saturday.

Don’t forget to send me your list of vegetables and fruits you ate over the weekend—and remember the ketchup!

What are you prepared to do today?

        Dr. Chet

Essential Tests: Bones and Body Fat

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After Saturday’s Memo, the logical question is: “How do I really know if I’m overfat?” This weeks Memos are going to be about tests. No, you don’t have to study for these tests. I’m talking about medical tests to talk about with your healthcare provider.

At this point, the best way to test for body fatness is using dual-energy X-ray absorptiometry (DEXA). This process uses low-beam radiation and can identify the three main tissues that make up our body: bone mass, lean mass, and fat mass. Yes, DEXA is the same technology that’s used to determine your bone mass to test for osteopenia and osteoporosis. Instead of just doing the wrist and pelvis, the entire body is scanned to determine body composition.

If you want to know your bone health and your body composition, check out the medical services in your area. There’s one hospital that offers DEXA for both purposes in Grand Rapids. If you’re over 40, it’s a great idea to do both tests. The bone scan will most likely be covered by insurance while you may have to pay for the body composition. The cost is about $100 in this area. If you want the most accurate method for bone mass and body composition, check out the DEXA availability in your area.

The goal is to use this information to improve your health. Reducing body fat and increasing bone mass both end up using a similar strategy: Eat less. Eat better. Move more. On Thursday another simple test that’s too often ignored.

What are you prepared to do today?

Dr. Chet-