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- BMI is not an accurate indicator of health because it does not take into account the percentage of body fat or the distribution of body fat.
- Also, BMI cannot accurately predict the health of different populations and races because it was created with data from only white Europeans.
- Measurements that are more accurate than BMI in predicting health outcomes include blood pressure, waist circumference, and cholesterol.
- Visit Insider’s Health Reference Library for more tips.
One of the most popular ways to measure body composition when it comes to health is the Body Mass Index (BMI). However, research indicates that BMI is not the most accurate representation and may have serious limitations in weight distribution, body fat percentage, and different demographics.
Here’s 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 their height in square meters (BMI = kg / m2). The results are divided into four categories:
- Underweight (<18.5)
- Normal (18.5 – 24.9)
- Overweight (25 – 29.9)
- Obese (> 30)
Doctors can use BMI measurements as a screening tool to tell which category you belong to and whether you are at increased risk for certain health conditions, such as
heart disease
or diabetes, depending on your results.
BMI was originally created in the 19th century by Belgian mathematician and statistician Lambert Adolphe Quetelet to measure obesity in the general population.
The formula then evolved in the 1940s, when the Metropolitan Life Insurance Company (MLIC) established an ideal weight standard for determining how much to charge clients for insurance based on their health.
“The MLIC developed the idea of a BMI classification to determine the height and weight of people in relation to their death,” says Fatima Cody Stanford, MPH, obesity physician and scientist at Massachusetts General Hospital. “But the problem with examining this historical data is that it did not 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, affordable, and easily accessible way to track a person’s health, the formula is better suited for information about populations in general, according to Stanford. When analyzing BMI at the individual level, there are several other factors to consider that BMI does not take into account:
1. BMI does not measure body fat percentage
Body fat percentage (BFP) is the percentage of fatty tissue in your body relative to your total body mass. It is normally measured with skinfold calipers, bioelectric impedance or, more specifically, through DXA x-ray analysis.
One of the main issues with BMI is that it can’t explain the difference between muscle and fat. Because muscle tissue is denser than fat, many athletes and bodybuilders are considered overweight according to BMI despite being in good athletic health.
“Body fat percentage will give a better assessment of health because disease risk is more correlated with body fat than with body weight,” says Chika Anekwe, MD, MPH, obesity physician at Massachusetts General Hospital and instructor at Harvard Medical School.
2. BMI does not take into account different demographic data
When Quetelet initially created the BMI, he extracted data from Anglo-Saxon organizations in an entirely European population. For this reason, it is not always an accurate representation of health for other demographic groups and races.
For example, researchers found that the obesity BMI cutoff for Asian populations is actually lower than the standard BMI chart. In 2004, the World Health Organization found that Asian people at high risk for type 2 diabetes and cardiovascular disease had lower BMIs.
Another large 2004 study of more than 15,000 Chinese adults found that a high risk of cardiovascular disease starts at a lower BMI and waist circumference than Caucasians. This means that when screening for BMI, Asian people may have a higher risk of disease in the categories considered healthy or normal on the BMI chart.
Additionally, 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, which is considered healthy. healthy is lower than the graph. For example, when measuring the risk of diabetes, black women approximate 33 and white women average 29.
“The bottom line is to personalize our patient care,” says Stanford. “This is 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 might see someone with a BMI of 32. , but it could actually be really healthy for them. in the context of their whole profile. ”
3. BMI does not measure the distribution of body fat
The specific location of fat is another important factor when considering overall health and is a measure for which the BMI does not adjust. Upper body fat around the midsection and visceral fat correlate more with health complications, such as cardiovascular disease, than lower body fat around the thighs and buttock area.
A 2017 study found that people with the same BMI can have very different risk profiles for heart attack, stroke, and diabetes depending on lifestyle, diet, and location of the disease. fat on their body.
“If we have fat in our midsection, it’s around our vital organs such as our heart or our liver, which can lead to bad risks,” says Stanford.
What are the most accurate predictors of health?
Anekwe says there are more accurate predictors of health than BMI. These are called the five metabolic risk factors. Together, they can increase your risk for heart disease, stroke, and diabetes.
These measures include:
- Waist size: Excess fat around the waist. If your circumference is 35 and over for a woman or 40 and over for a man, you may be at increased risk.
- High blood cholesterol: Overall cholesterol levels above 239 mg / dL in men and women may pose a higher risk for health problems.
- High triglycerides: A type of fat in your blood that can be high when you eat more calories than you burn. A high level of triglycerides is greater than 200 mg / dL.
- Arterial hypertension: When the blood flowing through your blood vessels is too high, also called hypertension. The arterial hypertension is 140/90 mmHg.
- High blood sugar: Blood sugar levels consistently above 125 mg / dL in adults, also known as hyperglycemia.
Takeaway from the insider
While measuring body mass index can be a quick and easy way to track your health outcomes, there are many caveats that BMI does not take into account, such as demographic differences, distribution. weight and body fat percentage.
In order to better understand your health, metabolic factors such as blood pressure and waist circumference can better predict your overall risk for certain health conditions.
If you are concerned about your BMI or your weight, it is completely normal and safe to consult your doctor or a health care professional to better understand what is personally healthy for you and your body.
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