- BMI is not an accurate predictor of health because it does not take into account the percentage of body fat or the distribution of body fat.
- Furthermore, the BMI cannot accurately predict the health of different demographic groups and races because it was created with data from white Europeans only.
- Measures that are more accurate than BMI to predict health outcomes include blood pressure, waist circumference and cholesterol levels.
- Visit the Insider Health Reference Library for more advice.
The body mass index (BMI) is one of the most popular ways to measure body composition with regard to health. However, research indicates that BMI is not the most accurate representation and may have serious limitations in weight distribution, body fat percentage and different demographic data.
Here is everything you need to know about BMI and weight measurement alternatives.
What is BMI?
BMI, or body mass index, is a calculation that estimates a person’s body fat by dividing their weight in kilograms by height in square meters (BMI = kg / m2). The results are divided into four categories:
- Low weight (<18.5)
- Normal (18.5 – 24.9)
- Overweight (25 – 29.9)
- Obese (> 30)
Doctors can use BMI measurements as a screening tool to indicate which category you fall into and whether you are at an increased risk for certain health conditions, such as
heart disease
or diabetes, based on your results.
BMI was initially created in the 19th century by Belgian mathematician and statistician Lambert Adolphe Quetelet as a way of measuring obesity in the general population.
The formula then evolved over the 1940s, when the Metropolitan Life Insurance Company (MLIC) installed an ideal weight standard to determine how much to charge customers for insurance based on their health.
“MLIC developed the idea of a BMI classification to determine what height and weight people were in relation to death,” says Fatima Cody Stanford, MPH, a physician and obesity medicine scientist at Massachusetts General Hospital. “But the problem with looking at this historical data is that it doesn’t include the diverse representation of individuals in the United States.”
No, BMI is not always an accurate measure of health
While BMI can be a quick, accessible and easily accessible way to track a person’s health, the formula is better suited for information about the general population, according to Stanford. When analyzing BMI at an individual level, there are several other factors to consider that BMI does not take into account:
1. BMI does not measure body fat percentage
The percentage of body fat (BFP) is the percentage of your body that is adipose tissue compared to your total body mass. It is usually measured with skinfold calibrators, bioelectrical impedance or, more precisely, by means of a DXA X-ray examination.
One of the main problems with BMI is that it cannot explain the difference between muscle and fat. Since muscle tissue is more dense than fat, many athletes and bodybuilders are considered obese according to the BMI, despite being at the peak of athletic health.
“The percentage of body fat will give a better assessment of health because the risk of disease is more related to body fat than to body weight,” said Chika Anekwe, MD, MPH, physician of obesity medicine at Massachusetts General Hospital and Harvard Medical School instructor.
2. The BMI does not take into account the different demographic data
When Quetelet originally created the BMI, he extracted data from Anglo-Saxon bodies in an entirely European population. Because of this, it is not always an accurate description of health for other demographic groups and races.
For example, the researchers found that the BMI obesity threshold for Asian populations actually falls below the standard BMI chart. In 2004, the World Health Organization found that Asians at high risk for type 2 diabetes and cardiovascular disease had lower BMI.
Another large 2004 study of more than 15,000 Chinese adults found that a high risk of cardiovascular disease started with a lower BMI and waist circumference than for Caucasians. This means that, when screening BMI, Asians may be at higher risk of disease in categories considered healthy or normal on the BMI graph.
In addition, Stanford conducted a study in 2020 that found that what is considered healthy for black women is higher than the standard BMI chart, while for Hispanic and white women, what is considered healthy is lower than the chart. For example, when measuring the risk of diabetes, black women fall close to 33 and white women on average 29.
“The main point to be conveyed is to personalize our patient care,” says Stanford. “It’s not a one-size-fits-all approach and we can’t expect everyone to need a BMI of 25. For black women, for example, you can see someone with a BMI of 32, but that can be really very healthy for them in the context of your entire profile. ”
3. BMI does not measure the distribution of body fat
The specific location of fat is another important factor when considering general health and is a measure for which the BMI does not adjust. Upper body fat around the middle and visceral fat are more related to health complications, such as cardiovascular disease, than lower body fat around the thighs and buttocks.
A 2017 study found that people with the same BMI may have very different risk profiles for heart attack, stroke and diabetes, depending on lifestyle, diet and the location of fat in their bodies.
“If we have fat in our midst, it is around our vital organs, like the heart or the liver, which can carry great risks,” says Stanford.
What are the most accurate health indicators?
Anekwe says there are health indicators that are more accurate than BMI. These are called five metabolic risk factors. Together, they can increase your chances of heart disease, stroke and diabetes.
These measures include:
- Waist circumference: Excess fat around the waist. If your circumference is 35 or more for a woman or 40 and more for a man, you may be at increased risk.
- High cholesterol: General cholesterol levels above 239 mg / dL in men and women may pose a greater risk for health conditions.
- Elevated triglycerides: A type of fat found in the blood, which can increase when you eat more calories than you burn. A high level of triglycerides is above 200 mg / dL.
- High pressure: When the blood flowing through the blood vessels is too high, it is also known as hypertension. The high pressure is 140/90 mmHg.
- High blood sugar: Blood sugar levels constantly above 125 mg / dL in adults, also known as hyperglycemia.
Insider Takeaway
While measuring your body mass index can be a quick and easy way to track your health outcomes, there are a number of caveats that the BMI does not address, such as different demographics, weight distribution and body fat percentage.
To better understand your health, metabolic factors like blood pressure and waist circumference can better predict the overall risk of certain health conditions.
If you are concerned about BMI or your weight, it is perfectly normal and safe to consult your doctor or health care professional to better understand what is personally healthy for you and your body.