Dr. Kumar explains...

How Found can help you reach a healthy weight with medical care and health coaching

What does BMI tell you?

BMI, or body mass index, tells you about the ratio of your weight to your height. Care providers, fitness coaches, and insurance companies use BMI to estimate body fat and gauge risk for weight-related health conditions, like heart disease. BMI has been used to measure potential disease risk rather than simply going by the number on a scale.  Some people use BMI to determine whether or not they need a weight loss plan.

But BMI isn’t perfect. Here’s why: 

  • A 19th century mathematician originally developed BMI as a screening tool to measure population health—not as a tool to gauge individual health. So when it comes to giving you rich health information, BMI has its limitations.

  • BMI doesn’t distinguish between fat mass and lean mass. So your body composition (your ratio of lean and fat mass) could change, but if your weight stays the same, so will your BMI, making it a poor way to gauge your risk for certain diseases.

  • The American Medical Association released a statement in 2023 urging health care providers not to use BMI alone to determine if someone is at a healthy body weight or at risk of certain conditions. 

The US Centers for Disease Control and Prevention (the CDC) recommends taking your BMI in consideration with other factors—such as a physical and lab results, such as checking for high cholesterol, high blood pressure, or blood glucose levels.

You should also consider your health behavior and habits, and other indicators of a healthy weight or risk of chronic disease.

Bottom line: BMI can only be a part of the picture when you’re interested in your health and weight. Do a little more investigating by using other tools or by visiting with a health professional.

How do I calculate my BMI?

You can use our BMI calculator to calculator your BMI, or you can do it yourself. If you’re using Imperial measurements (the most commonly used in the United States), follow these steps to calculate your BMI: 

  • Multiply your weight in pounds by 703.
  • Divide that answer by your height in inches.
  • Divide that answer by your height in inches again.

If you are using the metric system, divide your weight in kilograms by your height in meters squared. 

The standard BMI categories for adults are: 

  • Below 18.5 = under weight
  • 18.5–24.9 = healthy weight
  • 25.0–29.9 = overweight
  • 30 and above = obesity

There are different BMI ranges for children. The CDC has a BMI calculator for children 2 through 19, and it incorporates growth charts.

What are the cons of the BMI scale?

BMI has several cons. Because it can’t distinguish between lean and fat mass, it’s limited. It also doesn’t take age, sex at birth, and ethnicity into account. Here are details about how BMI is limited and some better ways to track your health and weight.

1. BMI doesn’t tell you where body fat is stored on your frame.

Carrying more weight around your middle—specifically visceral or belly fat—is a much more important predictor of obesity-related diseases such as type 2 diabetes, heart disease, and certain cancers, as well as overall mortality than total body fat levels. And BMI alone doesn’t use enough information to help you evaluate all those risk factors.  

2. BMI may not be an accurate health measure for certain ethnic and racial groups.

Crazy fact: The original calculations for BMI were developed nearly 200 years ago by a Flemish statistician. They were then updated in the early 1970s using data from only white European men. As a result, its ranges don’t apply fairly to other ethnic groups and people of color.

For example, research has shown that BMI isn’t a good measurement of health among people of Asian heritage because this group may have an increased risk for metabolic diseases before their height and weight calculation qualifies them as overweight. In the past, BMI has missed health problems among Asians.

That’s why organizations like the American Heart Association recommend that doctors use a different BMI scale for Asians that has lower healthy weight cutoff points. Studies have also shown that BMI is flawed in assessing health risks among Black Americans and people of African descent.  

3. BMI doesn’t consider your sex.

Women tend to have higher amounts of total body fat than men with equivalent BMIs. (We are referring to sex at birth.) Men also have more muscle, on average, than women. Yet, BMI calculations hold men and women to the same weight range standards. It’s also not a great gauge for pregnant and nursing women, who carry more weight and body fat to help nourish their babies. This has been shown not to pose any long-term health risks, despite their higher BMIs.

4. BMI can be particularly flawed among athletes.

One of the most famous examples of how BMI doesn’t work for athletes is Arnold Schwarzenegger. When the former California governor was in the prime of his bodybuilding career, he was 6’0” and weighed around 235 pounds—most of which was muscle, of course. His stats gave him a BMI of 31, putting him in the obese range. What’s more: A study of NFL players found that 60 percent of them would technically be considered overweight or obese according to the BMI chart. That doesn't seem quite right with all that training and weight lifting, does it? And that’s exactly the problem: BMI can’t measure overall body composition—meaning how much body fat you have versus lean muscle mass. Muscle is more dense and heavy than body fat, so it’s possible to fall into the “unhealthy” range even though that’s likely not the case.

5. BMI can underestimate body fat in older adults. 

Ever heard the term “skinny fat”? It describes those who are technically at a normal weight—or maybe even underweight—but have a high percentage of body fat that could pose a health risk. And BMI overlooks this. How does this impact older people? Because as you age, your body naturally loses muscle mass. (Well, without regular exercise, like strength training, to help you maintain it, that is.) This could give you a higher ratio of body fat to muscle—the official term is sarcopenic obesity, or ”skinny fat.” It can definitely occur in younger people, too, but it’s most common among elderly adults.

6. BMI can contribute to stigmas around weight.

There is already a lot of guilt and shame wrapped around the topic of weight. And when someone who is overweight or with obesity goes to the doctor, BMI tends to be the focal point of discussion. As a result, other health concerns could get pushed aside. Or that shame may keep people from seeking the preventative care they need, period. This can lead to higher rates of chronic conditions down the road.

Alternatives to BMI

There are more accurate ways to assess how much body fat you have—and your health.

Waist size

One of the easiest methods is to measure your waist circumference or the distance around your middle right at belly button level. This can help tell you how much visceral fat (belly fat) you have. Excess amounts are tied to health risks, including heart disease and type 2 diabetes. For men, waist circumference should be less than 40 inches; among women, the ideal is less than 35 inches.

You can also try a waist-to-hip ratio calculator.

Body composition

Another way to check your health is body composition or percent body fat, which looks at how much of your body is lean mass and how much is fat. According to the American Council on Exercise, women are considered to have obesity at 32 percent body fat, and 25 percent for men.

There are several ways to check body composition. For the most accurate measurement with detailed insights, you can get a DEXA scan (dual-energy X-ray absorptiometry), which costs between $150 and $400. Bathroom scales that use bioelectrical impedance are less accurate, but are accessible and can help you track change over time. The least expensive way to measure body fat is a skinfold test done with a pair of $10 to $15 skinfold calipers.

Body roundness index

BRI, or body roundness index, is a newer metric that takes waist size into account along with height and total weight. Some BRI calculators also take hip circumference, gender, and ethnicity into account. BRI is a better indicator for estimating risk for heart disease, cancer, and kidney disease than other tools, according to research published in the Journal of the American Medical Association.

What do you do after you use the BMI Calculator? 

If, after looking at BMI and several other indicators, you are concerned about your weight and health risks, seek out medical advice. The health care providers at Found are trained in obesity medicine. The reasons for weight gain are different for each person. Found’s clinicians can personalize a treatment plan for you to work specifically with your biology to target the root cause of your weight issues. Found also offers 1:1 health coaching—so you can work on healthy eating, physical activity, and other lifestyle changes to reach a healthy weight range.

Meet the author
The Found Team
Medically reviewed by:
Amanda Pusczek RN
Fact checked by:
Lisa Greissinger
Edited by:
Shaun Chavis
Last updated on:
November 14, 2024

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