You’ve no doubt heard of Body Mass Index before. The popular test uses a formula to evaluate your health based on your weight and height. According to the National Institutes for Health, if your score falls between 18.5 and 24.9, your weight is healthy. Anything below that is too low, scores between 25 and 29.9 are deemed overweight and 30 or higher is considered obese.
This seems like a relatively straightforward way to judge health—and indeed, many doctors use BMI as a screening test to gauge risk for certain conditions, like heart disease and diabetes. However, at second glance, there are a few things that may skew your BMI one way or the other. For one, the score doesn’t take into account gender and its natural implications for body mass type (for example, men have more lean mass than women). Also, BMI doesn’t separate lean muscle mass from body fat (it’s all rolled into body weight), leading to potentially higher scores for athletes and those who frequently work out.
It also might not be 100 percent accurate as a stand-alone predictive tool. According to a study in the journal PLoS One, about half of participating women not categorized as obese by BMI actually were obese according to body fat percentage. And on the flip side, a quarter of all participants classified as obese from their BMI weren’t actually when researchers looked at their body fat percentage.
With all that said, if you’re looking for an alternative to BMI, there are a few other tests. Body fat percentage, as mentioned above, separates lean muscle from fat to judge your health. There are several ways to calculate your body fat percentage (the skinfold measurement, which uses calipers to measure the thickness of your skin in different areas is one of the most common methods). Body adiposity index, which uses height and waist circumference to evaluate body composition, is another effective alternative, especially because larger waist size has been tied to increased risk for conditions like heart disease.
However, there is no one test that should be used to judge your health. The bottom line is that health care professionals need to be able to create a full picture of your personal health, and while not always accurate on its own, BMI can still be an effective tool in putting the picture together. Just don’t see it as a black and white reading on how fit you are.
Photo credit: Allan Foster