AMA Says "Bye Bye" To BMI
This Is The Beginning Of The End For BMI
"Did the American Medical Association Just Kill BMI?"
It's a question buzzing in everyone's mind since the American Medical Association (AMA) made a game-changing decision this week.
Instead of just focusing on the Body Mass Index (BMI), a common but sometimes misleading measure of health, they now suggest doctors should look at a broader picture when considering a patient's weight and health.
The AMA even acknowledged that using BMI alone has caused harm in the past and has even been used unfairly. The New York Times brought this significant news to the public's attention.
Dr. Cynthia Romero, who was part of the team that shaped this new policy, explained how crucial this change is. She said that doctors should consider more than just a number when it comes to patient's health - they should take into account the whole picture.
This perspective directly impacts folks like Mark Jenkins, a fitness enthusiast who has always found his BMI misrepresenting his actual health status. Mark shared, "I was always confused. I take care of my body, eat healthy and workout regularly, but my BMI was never in the 'ideal' range."
Another expert, Dr. Scott Hagan, a professor who has done a lot of research on weight problems, thinks this could be the first step towards a whole new way of looking at health. In his opinion, this change is a big deal. He believes that doctors in the past were too quick to tell people with high BMI numbers to lose weight, often without considering how this advice might affect them both physically and emotionally.
But we should remember that this new suggestion is not a hard and fast rule. It's more of a guidance for doctors, not a strict rule that they must obey. The new guideline encourages doctors to also consider factors like the amount of fat in a person's belly, how the fat is spread across their body, the ratio of bone and muscle, and even things like sugar levels in the blood and the functioning of their thyroid.
BMI is calculated by dividing a person's weight in kilograms by the square of their height in meters. Or use the CDC's BMI calculator. While it's a simple calculation, it doesn't always tell the full story about someone's health.
As Dr. Hagan told the New York Times, "The BMI is just a very poor measure of general health. Someone with an elevated BMI may be perfectly healthy."
That statement resonates with people like Dave Martin, a muscular guy who has a daily date with the weights. Despite his robust physique, his BMI categorizes him as 'overweight.' Dave, a little annoyed, shared, "I've been lifting weights since my teenage years. I'm fit, not fat."
Interestingly, the roots of BMI are based on data from a particular group of people - non-Hispanic white folks from past generations. This basis makes it hard to apply the measure to everyone.
Despite the challenges, BMI continues to be deeply embedded in our healthcare system. "A lot of our standards and guidelines were built around it," says Dr. Gutin. "Once that happens, it's challenging to change the direction."
However, this new suggestion does not eliminate the use of BMI completely. It simply advises doctors not to rely solely on it. Certain physicians, like Dr. Jack Resneck Jr., who recently stepped down as the president of AMA, still find BMI to be useful in certain situations. He stated that doctors should understand the benefits and limitations of using BMI as a measure of health.
Some experts, like A. Janet Tomiyama, a psychology professor, have been questioning the credibility of BMI for a long time. She told the Times she was "in shock" when the new policy came out and added, "For the longest time, I've been in this emperor-has-no-clothes situation, where I just couldn't understand why smart physicians continue to rely on something so clearly flawed."
Another reason why this move by the AMA is important is because BMI has a "complicated past," according to Leslie Heinberg, the director of the Enterprise Weight Management Center at the Cleveland Clinic. She pointed out that where we carry our weight matters.
Read our series on No-Diet Weight Loss.
For instance, fat in the abdomen can lead to higher rates of Type 2 diabetes and heart disease, compared to fat around the hips. This kind of detail is something BMI fails to take into account.
Take the case of Peter Adams, an avid dancer with a strong, lean body and a lifestyle centered around healthy eating and regular exercise. According to his BMI, Peter is considered 'overweight.'
"It feels like a bad joke," Peter confessed, "I've been a dancer all my life, and my body is lean and muscular. Yet, my BMI classifies me as 'overweight'. It's baffling and frustrating."
It's worth noting that at a broader level, BMI still has some value. According to Iliya Gutin, a program officer at the National Academies of Sciences, Engineering and Medicine, BMI is "probably the best we can do" when it comes to assessing large groups of people. It's simple, cheap, and quick. However, it’s essential to remember, as A. Janet Tomiyama emphasized, that BMI is “not this magic or powerful number that dictates how healthy or sick you’re going to be.”
The introduction of this new policy is a significant step forward in the field of healthcare. It signifies an essential shift towards a more nuanced, personalized approach to health and wellness. As we move forward, it's crucial that medical professionals contemplate these changes and understand what they mean for their patients.
This change encourages a more comprehensive, holistic approach to health, promoting the idea that every individual is unique, and their health cannot be distilled down to a single number. Instead, it needs to be understood in its entirety, with respect for the individual's lifestyle, body composition, genetic factors, and overall well-being.
In the end, the move by the AMA signifies a willingness to evolve and improve our understanding of health and wellness. It's a bold step towards a future where health is measured not just in numbers but in the overall quality of life.
It's a future where Mark, Dave, and Peter, along with countless others, can hope to have their health evaluated for what it truly is, beyond what a simple calculation on a scale might suggest.
What The AMA Suggests Instead of BMI
The very best way to measure fat is through DAX (a low-dose X-ray scan that can measure the amount of fat, bone, and muscle in the body) or an MRI, both of which are expensive and time-consuming.
You could also use calipers, but here's what AMA suggests as cheap alternatives that don't require any instruments:
The body adiposity index (BAI)
This is a method of estimating the amount of body fat in humans. It is calculated without using body weight, unlike the body mass index (BMI). Instead, it uses the size of the hips compared to the person's height.
To calculate your BAI, follow these steps (or just use this calculator)
- Stand up straight with your feet together.
- Measure your hip circumference with a tape measure.
- Measure your height in meters.
- Calculate your BAI by dividing your hip circumference by your height to the power of 1.5 and subtracting 18.
For example, if your hip circumference is 100 cm and your height is 1.75 m, your BAI would be calculated as follows:
BAI = (100 cm) / (1.75 m)^1.5 - 18 = 0.82
A BAI of 0.82 indicates that you have a moderate amount of body fat. A BAI of 0.9 or higher indicates that you have a high amount of body fat.
The BAI is a simple and easy-to-use method of estimating body fat. It is not as accurate as other methods, such as dual-energy X-ray absorptiometry (DXA), but it is a good option for people who do not have access to more expensive or time-consuming methods.
Here are some of the limitations of the BAI:
- It is not as accurate as other methods of measuring body fat, such as DXA.
- It is not as sensitive to changes in body fat over time.
- It is not as accurate for people who have a lot of muscle mass.
Despite these limitations, the BAI is a useful tool for estimating body fat and can be used to track changes in body fat over time.
Here's how you can check your body fat:
Waist size:
You can use a tape measure to check the size of your waist, just above where your hips start. For girls, if your waist is 35 inches or more, you might have too much visceral fat. For boys, the number is 40 inches or more.
Waist-to-hip ratio:
To find this, measure your waist size and your hip size (around the biggest part of your hips). Then, divide your waist size by your hip size. If the result is more than 0.85 for girls and 0.90 for boys, you might have too much fat in your belly. Or use this calculator.
Waist-height ratio:
Here, you divide your waist size by your height. Or use this calculator. The result should be no more than 0.5, for both boys and girls. Some doctors like this method because other ways might not tell the difference as well between visceral fat and the fat that's just under your skin.
How to Measure Your Body Fat Percentage
There's a myriad of techniques available to calculate body fat percentage, yet, the most precise methods aren't typically available for home use.
It can be quite discouraging to see little to no difference when you step onto the scale.
While it's natural to want concrete evidence of your progress, your body weight shouldn't be your primary focus.
Some individuals who are considered "overweight" are actually healthy, while others with "normal weight" could be unhealthy.
Conversely, your body fat percentage gives you insights into what your weight consists of.
In essence, it reveals the percentage of your overall body weight that is comprised of fat. The lower your body fat percentage, the higher your lean muscle mass.
Here are the top 10 methods to calculate your body fat percentage.
Skinfold Calipers
Skinfold measurements have been a standard method to approximate body fat for over half a century.
Skinfold calipers measure the thickness of your subcutaneous fat — the fat under your skin — at specified locations on the body.
The measurements are taken at either 3 or 7 distinct points on the body. The exact points used differ in men and women.
For women, the triceps, area above the hip bone, and either the thigh or abdomen are used for the 3-point measurement.
A 7-point measurement in women would also include the chest, area near the armpit, and area beneath the shoulder blade.
For men, the 3 points are the chest, abdomen, and thigh, or the chest, triceps, and area under the scapula.
A 7-point measurement in men would also include the areas near the armpit and beneath the shoulder blade.
Pros: Skinfold calipers are extremely affordable, and measurements can be done quickly. They can be used at home and are also portable.
Cons: The method requires some practice and basic knowledge of anatomy. Plus, some people might not like the feeling of their fat being pinched.
Availability: Calipers are affordable and simple to buy online.
Accuracy: The skill of the individual performing the skinfolds can influence the accuracy. Measurement errors can fluctuate between 3.5–5% body fat.
Body Circumference Measurements
Body shape can vary from person to person, and the shape of your body can give clues about your body fat.
Measuring the circumference of certain body parts is a straightforward method of estimating body fat.
For instance, the US Army uses a body fat equation that only requires an individual's age, height, and a few circumference measurements.
For men, the circumferences of the neck and waist are used in this equation. For women, the circumference of the hips is also considered.
Pros: This method is simple and cost-effective. All you need is a flexible measuring tape and a calculator. These tools can be used at home and are portable.
Cons: Body circumference equations may not be accurate for all individuals due to variations in body shape and fat distribution.
Availability: A flexible measuring tape is easily obtainable and very affordable.
Accuracy: The accuracy can vary broadly based on how similar you are to the people used to develop the equations. The error rate can be as low as 2.5–4.5% body fat, but it could also be much higher.
Dual-Energy X-ray Absorptiometry (DXA)
As suggested by its name, DXA utilizes X-rays of two different energies to calculate your body fat percentage.
During a DXA scan, you lie flat on your back for approximately 10 minutes as an X-ray scans you.
The radiation exposure from a DXA scan is very minimal, roughly the same amount you'd receive during three hours of your everyday life.
DXA is also used to evaluate bone density and gives detailed insights about bone, lean mass, and fat in separate body regions (arms, legs, and torso).
Pros: This method offers accurate and detailed information, including a breakdown of different body regions and bone density readings.
Cons: DXAs are often inaccessible to the general public, expensive, and emit a very small amount of radiation.
Availability: A DXA is generally only available in medical or research environments.
Accuracy: A DXA provides more consistent results than many other methods, with an error rate of 2.5–3.5% body fat.
Hydrostatic Weighing
This technique, also known as underwater weighing or hydrodensitometry, estimates your body composition based on its density.
This method weighs you while you're submerged underwater after exhaling as much air as possible from your lungs.
You are also weighed while you're on dry land, and the volume of air remaining in your lungs after you exhale is estimated or measured.
All this data is inserted into equations to determine your body's density, which is then used to predict your body fat percentage.
Pros: It's accurate and relatively quick.
Cons: Some individuals may find it difficult or impossible to be fully submerged underwater. This method requires you to exhale as much air as possible and then hold your breath underwater.
Availability: Hydrostatic weighing is usually only accessible at universities, medical settings, or certain fitness facilities.
Accuracy: When performed correctly, the error of this method can be as low as 2% body fat.
Instructional video: Here's an example of how hydrostatic weighing is performed.
Air Displacement Plethysmography (Bod Pod)
Like hydrostatic weighing, air displacement plethysmography (ADP) calculates your body fat percentage based on your body's density.
However, ADP uses air instead of water. The relationship between the volume and pressure of air allows this device to predict your body's density.
You sit inside an egg-shaped chamber for several minutes while the air pressure inside the chamber is adjusted.
To obtain accurate measurements, you need to wear skin-tight clothing or a swimsuit during testing.
Pros: The method is accurate and relatively quick, and it doesn't require being submerged in water.
Cons: ADP has limited availability and can be expensive.
Availability: ADP is typically only accessible at universities, medical settings, or certain fitness facilities.
Accuracy: The accuracy is excellent, with an error rate of 2–4% body fat.
Bioelectrical Impedance Analysis (BIA)
Bioelectrical Impedance Analysis (BIA) is a method that measures the body's resistance to small electrical currents.
By attaching electrodes to the skin, electrical currents are sent through the body, and the rate at which they return is measured. The quicker the currents return, the less body fat a person is likely to have, given that muscle, with its high water content, conducts electricity better than fat.
Different BIA devices offer varying degrees of precision and complexity, with price points to match.
Pros: BIA is an easy-to-use and rapid method for assessing body fat, and numerous consumer-grade devices are available.
Cons: The accuracy of BIA devices can fluctuate greatly and is often influenced by food and fluid consumption.
Availability: While consumer-friendly units are readily accessible, professional-grade models used in research or medical facilities tend to yield more precise results.
Accuracy: Precision can differ significantly, with error rates fluctuating between 3.8–5% body fat.
How-to videos: Here are examples of low-cost BIA devices featuring hand electrodes, foot electrodes, and both hand and foot electrodes. This is a demonstration of a more advanced BIA device.
In a nutshell: BIA devices measure body fat percentage by transmitting small electrical currents through the body and recording the speed at which they return. Though numerous devices exist, higher-end models generally provide more accurate results.
Bioimpedance Spectroscopy (BIS)
Bioimpedance Spectroscopy (BIS) resembles BIA in that both use small electrical currents to measure body composition. Although BIS and BIA machines may look similar, they employ different technologies. BIS uses a broader range of electrical currents and frequencies to estimate body fluid volume.
BIS also interprets data differently, and some experts believe BIS to be more precise than BIA. Despite this, both BIS and BIA use the body fluid data they collect to estimate body composition.
Pros: BIS is a fast and straightforward method to use.
Cons: Unlike BIA, BIS devices for home use aren't readily available.
Availability: BIS is primarily available in educational institutions, medical environments, or specific fitness centers.
Accuracy: BIS is typically more accurate than BIA models intended for home use, although it is comparably accurate to higher-end BIA devices.
Electrical Impedance Myography (EIM)
EIM, another method that utilizes small electrical currents to measure body fat, targets specific body parts, unlike BIA and BIS that analyze the whole body. Recent developments have made EIM devices more affordable and accessible to consumers. These devices estimate body fat in specific areas, similar to skinfold calipers in principle, albeit through distinct technology.
Pros: EIM is relatively quick and straightforward to use.
Cons: Not much data exists about the accuracy of these devices.
Availability: EIM devices are readily accessible and affordable for the general public.
Accuracy: While limited data is available, one study reports an error rate of 2.5–3% compared to DXA.
3-D Body Scanners
3-D body scanners employ infrared sensors to create a detailed 3-D model of the body. Some scanners require you to stand on a rotating platform, while others rotate sensors around your body. The generated data is used to estimate your body fat percentage based on your body shape, thus making it similar to circumference measurement methods, but providing a more comprehensive data set.
Pros: 3-D body scanning is relatively quick and simple.
Cons: 3-D body scanners are not widely available but are gradually gaining popularity.
Availability: Some consumer-grade devices are available, but they are not as cost-effective as basic measurement methods like skinfold calipers.
Accuracy: Although limited information is available, some 3-D scanners may be fairly accurate, with error rates of around 4% body fat.
Multi-Compartment Models (the Gold Standard)
Regarded as the most accurate body composition assessment method, multi-compartment models break down the body into three or more components. These models require various tests to estimate body mass, volume, water, and bone content.
Data from the tests mentioned earlier in this article are combined to build a comprehensive image of the body and achieve the most precise body fat percentage estimation.
Pros: This method offers the highest accuracy.
Cons: It's often inaccessible to the general public due to its complexity and the need for multiple different assessments.
Availability: This technique is usually only available in select research and medical facilities.
Accuracy: With error rates potentially under 1% body fat, these models are the best available and serve as the gold standard for comparison.
In a nutshell: Multi-compartment models are highly accurate and considered the benchmark for body fat assessment. However, they require multiple tests and are not generally available to the public.
Choosing the Best Method for You
Choosing the best method to measure body fat percentage can be challenging. Here are some questions to consider:
- What's the purpose of measuring your body fat percentage?
- How accurate do you need the results to be?
- How frequently do you plan on testing your body fat percentage?
- Would you prefer a method that can be performed at home?
- How much are you willing to spend?
Simple and affordable methods like skinfold measurements, circumference calculations, and portable BIA devices can be used at home whenever you like. These might be the best choice for you despite not being the most accurate.
Higher-accuracy methods are usually not available for home use and can be costly when available at a testing facility.
If accuracy is a priority and you're willing to pay for it, you might consider methods like hydrostatic weighing, ADP, or DXA.
Regardless of the method you choose, consistency is crucial. For most methods, it's best to measure in the morning after an overnight fast and before starting your day.
Even the best methods are not perfect and only provide an estimate of your true body fat, so it's essential to interpret your results with caution.
