Body mass index, or BMI, has been used for over 100 years to help health professionals decide whether a patient is overweight or underweight. The team of researchers behind RFM say it’s more accurate than BMI, and it can also be worked out with just a tape measure – so you don’t need a set of scales to calculate it, as you do with BMI. Other scientists, however, have suggested that although some people may appear to be overweight but healthy, the extra weight still puts them at higher risk of certain diseases as they get older. As a service to our readers, Harvard Health Publishing provides access to our library of archived content. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
For example, muscle weighs more than fat, so athletes or someone who is more muscular could be deemed “overweight” by their BMI even though they may be metabolically healthier than someone whose BMI is in the “normal” range with who has less muscle. Another 21 million people were classed as “normal” in terms of BMI but were later determined to be unhealthy based again on those other cardiometabolic measures. In order to more accurately understand your health, metabolic factors like blood pressure and waist circumference can better predict your overall risk for certain health conditions. Measurements that are more accurate than BMI at predicting health outcomes include blood pressure, waist circumference, and cholesterol levels. You should always speak with your doctor or other qualified healthcare provider before you start or change any weight management or physical activity plan.
“MLIC developed the idea of a BMI classification to determine what height and weight people had relative to their death,” says Fatima Cody Stanford, MPH, an obesity medicine physician and scientist at Massachusetts General Hospital. “But the problem with looking at that historical data is that it did not include the diverse representation of individuals in the United States.” As a single measure, BMI is clearly not a perfect measure of health.
Researchers found that 54 million Americans had been classed as overweight or obese, but cardiometabolic measures showed they were healthy. Another 21 million were classed as “normal” in terms of BMI, but they were unhealthy. For a woman, 10 to 13 percent fat is healthy, but over 32 percent is considered a sign of obesity. One suggestion is to combine BMI with waist circumference for a more accurate measure. Trefethen argued that the formula leads to confusion and misinformation. The height term, he says, divides the weight by too much when people are short, and by too little when they are tall.
This typically involves measuring the thickness of skin folds at different places on the body. More expensive, yet precise, options include DEXA and underwater weighing, but these aren’t practical for most people. So, according to the BMI, the sprinter is more overweight than the sedentary person. But as I said earlier, a glob of muscle weighs about 18 percent more than the same size glob of fat, so this is clearly not an accurate statement.
But it turns out that there are some real problems with using these categories as a way to determine a person’s overall health or even body composition. Now, imagine a sprinter who is also six feet tall but weighs 211 lbs. The formula then evolved through the 1940s when the Metropolitan Life Insurance Company installed an ideal weight standard to determine how much to charge clients for insurance based on their health. Our stories are reviewed by medical professionals to ensure you get the most accurate and useful information about your health and wellness. Research suggests that BMI alone frequently misclassifies metabolic health, which is linked to how much fat a person has and how it is distributed.
That being said, BMI is fairly indicative of body fat for 90-95% of the population, and can effectively be used along with other measures to help determine an individual’s healthy body weight. The BMI is a straightforward numeric ratio and doesn’t take health of ketogenic into account how any particular body is put together. “Every body is so different in terms of overall structure, sex differences, and cultural differences,” says Dr. Lee, and these factors matter when it comes to determining a person’s health.
According to the National Institutes of Health, a bigger waist circumference is linked to a higher risk of type 2 diabetes, high blood pressure, abnormal cholesterol levels, and heart disease when BMI is 25 to 34.9. Another large 2004 study of over 15,000 Chinese adults found that a high risk for cardiovascular does creatine expire disease started at a lower BMI and waist circumference than for Caucasians. This means when screening for BMI, Asian people may have a higher disease risk in categories considered healthy or normal on the BMI chart. Her research also found that the WHtR measurement is more precise at measuring life expectancy.
According to a report in the August 2006 New England Journal of Medicine, excess body weight during midlife is associated with an increased risk of death. The current BMI definitions of overweight or obesity were based largely on white populations. Yet body composition, including percent body fat or amount of muscle mass, can vary by race and ethnic group. So, BMI may help predict health status among people who are white, but may be less accurate for people in other racial and ethnic groups. BMI, as a single measure, would not be expected to identify cardiovascular health or illness; the same is true for cholesterol, blood sugar, or blood pressure as a single measure. And while cardiovascular health is important, it’s not the only measure of health!
In this case, an elderly person’s BMI could be within a normal range while they might actually be overweight. Well, imagine a sedentary person who is six feet tall and weighs 203 pounds. Beyond assigning one of these categories, a high BMI can be also an indicator of high body fat and therefore can be used to screen for certain weight levels that could lead to health problems.
In 2004, the World Health Organization found Asian people with a high risk for type 2 diabetes and cardiovascular disease had lower BMIs. One of the main issues with BMI is that it cannot account for the difference between muscle and fat. Because muscle tissue is more dense than fat, many athletes and bodybuilders are considered overweight according to BMI despite being in peak athletic health. For a man, 2 to 4 percent fat is considered healthy, and over 25 percent is classed as obesity.
These charts were cumbersome to use, and it was never clear how one was to decide a person’s “frame size.” The Body Mass Index has been relied on as the tool to measure relative fat levels and weight status for decades. It first came 7 graphs prove calories count into popular use in the early 1970s, when the famous American physiologist Ancel Keysgave the formula, devised in the 1840s, a new name. Among government health agencies and doctor offices everywhere, it became and remains king.
A glob of muscle weighs about 18 percent more than the same size glob of fat. As most of us fitness-focused folks have likely heard, BMI is far from a perfect measurement. Much of the time, and often when it really counts, the BMI measurement may actually overestimate or even underestimate a person’s body fat. Just use a soft tape measure around your bare midsection at your belly button.
When compared to white Europeans of the same BMI, Asians appear to have a four percent higher total body fat. South Asians, in particular, have especially high levels of abdominal obesity, which can throw off the BMI measurement as well. Body mass index is one of the most popular ways to measure body composition as it pertains to health. However, research indicates BMI is not the most accurate depiction and can have serious limitations in weight distribution, body fat percentage, and different demographics.