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This BMI Calculator Won’t Give You an Accurate Measure of Overall Health

Body mass index is only one part of an overall assessment of your health and not very useful for athletes, in particular.

bmi calculator
David Jaewon Oh

How to Use the Following BMI Calculator: This tool calculates your body mass index (BMI), which is a measure of your mass relative to your height. Our calculator accounts for the fact that, in healthy people, weight and height don’t usually increase linearly. A simple formula that says you should weigh a certain number of pounds per inch of height doesn’t provide as accurate a guide to what’s a healthy weight.

Enter your height and weight below. The resulting number is your BMI. But note that your BMI is only one part of an overall assessment of your health (more info on this below).

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For decades, healthcare professionals have used Body Mass Index (BMI)—a measure of how much mass someone has relative to their height—to identify whether a patient is at a healthy weight.

Public health experts have established the following general guidelines for interpreting BMI results, although, as we’ll see below, these ranges might not accurately portray any one person’s situation.

  • 18.4 or lower: Underweight
  • 18.5 to 24.9: Healthy weight
  • 25 to 29.9: Overweight
  • 30 or higher: Obese

    But BMI is only one part of an overall assessment of your health. In large studies, people’s risk for conditions such as diabetes, high blood pressure, and heart disease increase above a BMI of 25. In the same studies, these and other health risks, as well as the likelihood of dying at an early age, go up dramatically for people with a BMI of 30 or greater.

    Of course, it’s possible to be in the “healthy weight” range and have an unhealthful lifestyle; a small-framed person who smokes, never exercises, and shows signs of or has a history of disordered eating could have a lower BMI than an active non-smoker who follows a healthier diet.

    Similarly, it’s possible to be muscular and have relatively low body fat but still have a BMI in the “overweight” range. As athletes, we tend to have a higher proportion of muscle tissue, which by nature is denser than fat tissue. That means we sometimes see big numbers on the scale even if we have relatively low body fat.

    BMI also says nothing about how your fat is distributed. Two people may have identical BMI measurements (“healthy” or otherwise), but where one might store most of their fat as deep abdominal, visceral fat—which is known to be a high health risk—the other might store it as relatively innocuous subcutaneous fat (the kind you pinch under your skin). In general, large stores of deep abdominal fat pose a greater health risk than the same amount more evenly distributed throughout your body.

    Additionally, research published in the International Journal of Obesity looked at data from over 40,000 people and analyzed the link between BMI and key health markers including blood pressure, glucose, insulin resistance, cholesterol, and triglyceride levels. The results revealed that there was no strong connection between BMI and overall health. Researchers found that nearly half of overweight men and women and 29 percent of obese people were otherwise totally healthy. On the flip side, more than 30 percent of those with normal BMIs were actually unhealthy according to those markers.

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    The takeaway: Use your BMI as only one part of an overall assessment of your health. If you’re concerned about your BMI or your healthcare provider raises a red flag over yours, A. Janet Tomiyama, Ph.D., associate professor of psychology at UCLA who directs UCLA’s Dieting, Stress, and Health Lab, suggests gathering more data for a fuller picture of your weight, health, and fitness. A body composition test performed with a DEXA scan, skinfold caliper test, or bio-impedance scan (like a Tanita scale) can give you a better idea of your actual body composition, so you know how much of you is lean, muscle tissue relative to fat. Some gyms and health clubs even offer these services. Also, see your doc and round up your general health metrics.

    But in general, emphasize healthful behaviors—regular running and other activities, eating healthy foods, and not smoking—over basing lifestyle decisions on a certain BMI reading.

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