Let's talk about body mass index

Until recently, the medical field relied on one test to measure whether a patient’s body fat was in a healthy or unhealthy range: Body Mass Index, or BMI.

Advancements in medicine have shed new light on why BMI is not the be-all and end-all of weight loss progress or goal setting we once thought it was.

How to calculate your BMI

BMI is a simple calculation — a little too simple, according to its detractors. Here’s the formula:

1. Multiply your weight (lbs) by 703.
2. Divide that number by your height (in).
3. Divide that number again by your height (in).

The problem with BMI testing

One of the BMI scale’s most outspoken critics is the American Medical Association (AMA). In 2023, the AMA even adopted a new policy warning against the use of only factoring BMI in measuring and diagnosing obesity, noting multiple inaccuracies and inherent flaws.

“Due to significant limitations associated with the widespread use of BMI in clinical settings, the AMA suggests that it be used in conjunction with other valid measures of risk.”

Physicians have traditionally regarded BMI as a reliable, one-and-done measurement tool. However, most now concur with the AMA in questioning its accuracy and legitimacy as a standalone method.

What this means for your weight

Falling short of where a BMI chart says you should be, weight-wise, can be discouraging. But don’t let it get you down; here are a few specific issues with BMI:

• It doesn’t count muscle. BMI only measures weight and height, so skeletal muscle index is not a part of its equation. This means the entirety of a person’s weight is considered fat. Therefore, someone who is overweight, with little muscle mass, might have a similar BMI to someone with a significantly different muscle and body fat index.
• It’s antiquated. BMI was devised almost 200 years ago using only men of European descent as a baseline for “normal” weight and, therefore, health. We have since learned that body fat varies across people of different ethnic backgrounds, genders, and ages.
• It discounts age. It bears repeating that the current BMI model largely ignores a person’s age when measuring body composition — which is especially problematic for those over 65. Our fat-to-muscle ratio changes as we age, which can result in an erroneous obesity diagnosis.

The bottom line

Frustrated about your BMI? Remember, BMI is flawed when used alone to determine your ideal weight and other health risk factors. GOLO is in agreement with the medical professionals who have concluded that BMI should be used as part of a holistic measurement in tandem with other assessments. BMI is only part of the picture; keep working toward your goals and place less stake in your score.

Sources

Information for this article was collected by the health and wellness experts at GOLO using the following sources:

Yale Medicine

AMA

Hopkins Medicine

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