Tag Archive for: body mass index

BRI: It Just Doesn’t Matter

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Continuing our look at the BRI, the mathematician demonstrated that BRI is associated with body fat distribution. It makes sense; the waist measurement would provide an indication of fat around the waist. The next question is: would the BRI be a better predictor for cardiometabolic disorders than BMI?

BRI and Mortality

A group of researchers decided to use open-source data from the National Health and Nutrition Examination Survey database to examine the relationship between BRI and all-cause mortality. They coincided with the years that physical assessments were done including height and waist circumference; body weight was collected but not used in this instance. The time period began in 1999 and continued every two years through 2018.

There were two observations that were significant. First, in every demographic group, regardless of age, gender, or race/ethnicity, the BRI has increased during every examination period. As a country, the U.S. has gotten fatter. That matches every other measure such as body weight or BMI as well.

The second observation was that the hazard ratio (HR) increased as the BRI dropped below normal, then normalized when the normal BRI was reached, and the HR rose again as the BRI increased. Simply stated, there was an increased risk of mortality when people were too lean or too fat.

You may be wondering why I don’t give you a formula to do calculations for yourself. It’s very complicated and there are BRI calculators available on the website below. The main reason is that it just doesn’t matter—the BRI is no better at predicting mortality than the BMI. The researchers had the body weight data they needed to compare the BRI with the BMI directly. They just didn’t do it. However, looking at the mathematicians’ validation study, the categories of adiposity associated with BMI matches up quite well with the BRI and thus with body fatness. There’s no need for any more precision than is achieved with BMI.

The Bottom Line

It’s really the clinical use that seems to bother everyone, but with rare exceptions, the BMI gives an indication of body fatness. If physicians or other health care professionals cannot see the patient before them and realize they are too lean or too muscular to fit the typical interpretation of BMI, the fault lies with them, not the tool they are using.   

What are you prepared to do today?

        Dr. Chet

References:
1. JAMA. 2024; 332(16):1317-1318. 10.1001/jama.2024.20115
2. JAMA Netw Open. 2024; 7(6):e2415051. 10.1001/jamanetworkopen.2024.15051.
3. https://doi.org/10.1002/oby.20408
4. https://bri-calculator.com/#calculator

Body Roundness Index

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The Body Mass Index (BMI) has been used to provide an indication of whether someone is under weight, normal weight, overweight, or obese and the degree to which they are obese. There’s no measure of percentage of body fatness implied, but physicians and other medical professionals have used it for that purpose for a couple of decades. Why? It can be used to assess the potential risk of developing cardiovascular disease, pre-diabetes, and other metabolic conditions.

I happened upon a commentary in JAMA on the Body Roundness Index or BRI for short. It was published in response to a recent study published in a JAMA Network Open by researchers who examined the relationship between BRI and mortality.

Let’s start with this: what is the BRI? The BRI was developed by a mathematician. The reason was interesting; the developer told the commentator that the BMI is based on a “cylindrical” model but when she looked in the mirror, she felt she was more egg shaped. What she did, as a mathematician, was develop a model based on an “ellipse.” Why? She gave a couple of reasons.

The first reason is that BMI can misclassify individuals because it fails to distinguish between individual amounts of fat-free mass (FFM) and fat mass (FM). BMI also does not provide information about the distribution of body fat—specifically, visceral fat versus subcutaneous fat. She developed a mathematical model, to assess body fatness which would indicate where the fat is distributed. With some very complicated math, she developed the BRI. It uses only two measurements: height and waist circumference. The benefit of using the BRI is that it may be a better predictor of body fat than the BMI. Is it? We’ll check out the research study that began this examination of BRI on Saturday, because as Shaq famously said about getting in shape, “Round is a shape.”

The Insider Conference Call is tomorrow night. If you become an Insider by 8 p.m., you can participate in the call to get your questions answered.

What are you prepared to do today?

        Dr. Chet

References:
1. JAMA. 2024; 332(16):1317-1318. 10.1001/jama.2024.20115
2. JAMA Netw Open. 2024; 7(6):e2415051. 10.1001/jamanetworkopen.2024.15051.
3. https://doi.org/10.1002/oby.20408

COVID-19 and Obesity

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Obesity may be a contributing factor to the severity of symptoms for those who get COVID-19. The best explanation I’ve found why that may be true is in a paper in Nature Reviews Endocrinology published in April. There are several reasons in addition to the cardiovascular and endocrinological co-morbidities associated with obesity.

Just a reminder, by definition obesity is a Body Mass Index (BMI) greater than or equal to 30.0 kg/meters squared; it’s a measure of surface area. You can check yours at the Health Info page on the Dr. Chet website; it also includes the info to determine if you’re really big boned, because that has an impact.

The increased risks associated with obesity are driven by the respiratory system:

  • Impaired respiratory mechanisms
  • Increased airway resistance
  • Impaired gas exchange
  • Low lung volume
  • Low muscle strength

In effect, the greater the obesity, the more difficult it is to breathe deeply and when deep breaths are taken, the resistance within the airway and the actual exchange of oxygen and carbon dioxide are impaired. If required, intubation is more difficult. The greater the degree of obesity, the more difficult it is to provide regular patient care if someone is hospitalized with the virus. Add to all that the co-morbidities of the cardiovascular and endocrinological systems, and it makes recovery very difficult. More research is needed, but it’s a serious issue in a country where over 40% of all adults are obese.

I’ll wrap this up on Saturday with some thoughts about what we don’t know that could be impacting the development of treatments for the COVID-19 virus.

Facebook Messenger

I try to make myself as accessible as possible, and Insiders and Members have quicker access. My website contains a way to email me if you have a question. One way I’m no longer going to accept questions is via Facebook Messenger, so please use one of the other avenues.

What are you prepared to do today?

        Dr. Chet

Reference: Nature Reviews Endocrinology volume 16, pages341–342. (2020)

What’s Your Body Mass Index?

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You may be tempted to measure how you’re doing on the way to your health goals with body composition read-outs on scales and other outputs related to body fat analytics, but how accurate are they? If the device used is one that has you stand on a scale or hang on to handles of some sort, the accuracy of those numbers is very limited.

Those devices are based on impedance technology—the resistance of a very small current passed through your body. It actually can be very accurate when it comes to total body water, something very important for people with congestive heart failure. Everything else is based on algorithms that assume specific characteristics of the body. Those may be valid assumptions, but the variability is too great person to person. How do I know that? I worked on the impedance device as a grad student, so I know it well.

If you really want to track how you’re doing related to fatness, use the Body Mass Index. Every health insurance company uses that as a metric to assess your fatness.

“But I have bigger bones!” you say. Or maybe the weight recommended for you seems too high. In fact you may have a larger or smaller frame than average, and I explain how to know for sure with an easy measurement in the Health Info section titled Body Mass Index. Check it out today for an in-depth look at BMI.

What are you prepared to do today?

        Dr. Chet

Normal BMI but Still Too Fat

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Last week the health headlines shouted “Study Shows Over 90% of All Americans Are Overfat!” The rate of overweight as assessed by Body Mass Index (BMI) is already 70%; now scientists want to say even more people are too fat? What’s going on? I’ll explain what overfat means first and then tell you about the study behind it.

For the most part, the greater the BMI, the greater the risk for cardiovascular disease, prediabetes, and hypertension. For those of you who aren’t sure of your BMI, check out your BMI in the Health Info section of our website. And if you think you’re just big boned, we show you how to prove it.

But there are people who have a normal BMI under 25.0 but still may be overfat. Considering Waist Circumference in addition to BMI may help but that could still miss some people. How? They may have lost muscle mass; the subtle loss of lean muscle with a gain of fat could lead to overfatness. That increases their risk for the diseases I mentioned earlier.

Here’s the most common example of someone who has a normal BMI but is overfat: a very sedentary elderly person who looks slim, but has very little muscle. As the saying goes “use it or lose it” and they’ve lost it.

A clinician from Arizona has taken it upon himself to redefine the terminology associated with excess body fat. He claims that overfatness gets missed in too many people. The problem he sees is that people who could begin treatment with diet, exercise, and medication if necessary are being missed. He outlined his arguments in a paper published in January 2017 (1), but it was his paper published in July that lead to headlines (2).

He and his co-authors examined the BMIs of people in countries all over the world. Using prior studies that estimated the number of normal-weight people who are overfat, ranging from 9.7% to 20%, he then applied that to the normal-weight populations (as assessed by BMI) in the top 30 developed countries in the world. That’s how they derived the headlines of over 90% overfat—not just in the U.S. but also New Zealand, Iceland, and Greece as well. To be fair, this applied only to males. Don’t rest on your laurels, ladies. All the same countries were greater than 80% for females.

 

The Problems

There are three with his approach in my opinion. First, adding another definition to replace BMI doesn’t really help people or their physicians as he implies. Confirming a person with normal BMI is overfat would require a more advanced exam or assessment of body fat. I’m not sure that’s practical.

Second, I looked at his work from every direction and couldn’t get the numbers to work. If 70% of Americans are overweight or obese and you add 20% of the remaining 30%, it adds up to 76% not 90%. Even if the numbers worked, the statistic would apply to a physician’s total number of patients. There would be no way to identify who is overfat without additional testing.

Third, there’s another group that needs to be addressed, and that would be those who are overweight according to their BMI but are metabolically healthy. In fact, that’s a significant problem today. Even after losing over 30 pounds, my BMI is still in the overweight category. By every test of metabolic fitness—blood pressure, cholesterol, HbA1c, or insulin—I’m at no additional risk of heart disease, yet I’m still classified as “at risk” due to my BMI. I think that’s a greater issue and will be more so as healthcare gets debated. Is your BMI over 25? You’ll pay more, even if your test results are stellar.

 

The Bottom Line

I agree with the concept that the author put forth: there are people with normal BMIs that are overfat, and they’re at greater risk for CVD and metabolic diseases. But new definitions aren’t necessary. What is necessary is identifying who is at risk. That will only occur when doctor and patient meet face to face. When was your last doctor’s appointment?

What are you prepared to do today?

Dr. Chet

 

References:
1. Front. Public Health 4:279. doi: 10.3389/fpubh.2016.00279.
2. Front. Public Health 5:190. doi: 10.3389/fpubh.2017.00190.

 

BMI, WHR, and Lifestyle

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The study we’ve been examining is interesting on so many levels: large numbers of subjects; new statistical techniques due in large part to progress in computing capabilities; genetic analysis that allows for rapid analysis and identification of polymorphisms. It’s all very exciting. You’re probably anticipating a “but” coming and you’d be correct.

This study demonstrated that when using genetic information, WHR is a risk for CVD and type 2 diabetes even with a normal BMI. But there’s still at least two factors to consider that are dependent on each other.

First, just because someone has a mutated gene or genes, it doesn’t mean it will ever express itself, i.e., turn on. More than likely, the second factor has a role to play and that’s the lifestyle of the individual. Some studies refer to it as environment, but they’re intertwined. Where you live may limit or provide you with easy access to healthier foods. It may be easier to exercise in the suburbs than in a large city, or just the opposite given the park systems in different areas of the countries.

Then there’s the home environment: what foods you ate growing up and what your diet is now. All these can impact whether some genes may be expressed. Others may express themselves only when you get to a specific weight or fat intake. The variables are too numerous to consider.

I’m not attempting to confuse the issue. I just want you to know that while this study provides insight that we didn’t have before, you don’t have to be overly concerned. If you keep to a normal BMI and WHR, less than 0.9 for men and less than 0.8 for women, your risk for CVD and type 2 diabetes will not be high.

When all is said and done, it still comes down to three things. Eat less. Eat better. Move more.

What are you prepared to do today?

Dr. Chet

 

Reference: JAMA. 2017;317(6):626-634.

 

Waist-Hip Ratio vs. BMI

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In Tuesday’s message, I said researchers used a unique approach to answering the question of whether waist-hip ratio (WHR) is associated with cardiovascular disease and type 2 diabetes regardless of BMI. They found 48 genes which were associated WHR, a unique approach using the genetic information with Mendelian randomization of epidemiological data. If that isn’t a brain-full, I don’t know what is. Let me see if I can break it down for you.

As I’ve said many times before, epidemiological data cannot show cause and effect; they’re just observations. By using the genetic information related to WHR, researchers can analyze the data by statistically removing the effect of BMI. Because the genetic traits follow some randomization based on Mendel’s genetic work, if the WHR is still associated with the increased risks of disease, that means that where you carry your body fat is important, whether your BMI says you’re overweight or not.

They found that WHR is an independent risk factor for CVD and type 2 diabetes, confirming that the location of your body fat is important regardless of your BMI. That may be why people with a high BMI but low WHR have normal blood pressure and cholesterol levels while others with a normal BMI but a high WHR may have high numbers.

What are you prepared to do today?

Dr. Chet

 

Reference: JAMA. 2017;317(6):626-634.

 

Redefining the Risks of Extra Weight

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Studies show that 70% of the population is overweight; by definition, that means that their body mass index (BMI) is greater than 25 or more. But are all overweight people at the same risk? Just because you’re overweight, are you automatically at greater risk for cardiovascular disease and type 2 diabetes?

That’s what a group of researchers in the U.S. attempted to find out. They had the benefit of access to the U.K. Biobank, an independently funded databank that has collected biometric data on over 500,000 subjects in the U.K. and contains accurate measures of BMI as well as the waist-hip ratio (WHR) on all subjects. They also had one more thing: the genetic information on a large sub-group of subjects. They identified 48 genes that seemed to be associated with WHR and used a unique approach to tease out the effects of WHR from BMI. I’ll cover that the rest of the week.

In the meantime, check out your BMI and measure your waist and hip to calculate your WHR. Measure your waist about an inch below your belly-button and your hips at the widest point; divide waist by hips and you have your ratio.

What are you prepared to do today?

Dr. Chet

 

Reference: JAMA. 2017;317(6):626-634.

 

Prediabetes Risk Factors

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Based on the recently published study that showed only about 12% of those who were pre-diabetic realized it, it’s time to provide you with a list of risk factors for prediabetes. Let’s get right to it.

Weight
The higher your Body Mass Index, the greater your risk. You can check out your BMI in the Health Info section of drchet.com.

Waist Circumference
The larger your waist, the greater the risk. Men should be less than 40 inches and women less than 35 inches . . .

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How Fat Are We?

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Sometimes I miss Jay Leno. There were times he would ask a question such as “How fat are we?” and hit one-liner after one-liner. While his jokes were usually outrageous, they were indicative of where we are in the U.S. today. I’m going to review a couple of studies this week and believe me, there are no jokes in the latest research.

To answer Jay’s question, we’re fatter than we’ve ever been (1). Based on statistics from the Centers for Disease Control (CDC), the percentage of Americans who are overweight is 68.5 . . .

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If you're already a DrChet.com Member or Insider, click on the Membership Login link on the top menu. Members may upgrade to Insider by going to the Store and clicking Membership; your membership fee will be prorated automatically.