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BMI Is Not the Most Accurate Way to Measure Body Flab — But Here’s What Is

The body mass index (BMI) has been widely used for years to measure body fat in doctors’ offices and private homes all across the country. For those of us trying to lose weight or belly fat, we’ve often calculated our own BMI to track our progress. But according to new research, we might need to start checking our relative fat mass index (RFM) in the future instead.


The August 2018 study, published in Scientific Reports, identified a simpler and more accurate way of measuring body fat than the BMI: the RFM. As you can probably guess, the RFM is quite a bit different from the BMI. The BMI formula uses both your height and your weight to calculate your number, which in turn is used to determine whether you’re underweight, overweight, obese, or have a normal weight. It’s not exactly a secret that many experts consider the BMI to be an inaccurate measure of body fat; after all, a BMI cannot distinguish between body fat, bone mass, and muscle. Heck, by the BMI standards, a lot of bodybuilders might be considered “overweight” or even “obese.” (Though if you’re still curious, you can calculate your BMI here.)

The RFM, on the other hand, only uses your height and weight circumfrence measurements — but it still does a better job than the BMI at calculating your body fat percentage, experts say. In the study, researchers looked at more than 300 potential formulas for estimating body fat using a large database of 12,000 adults. Then, they calculated the RFM for 3,500 patients and compared the results to the participants’ outcomes from a high-tech body scan known for accurately measuring body fat, along with tissue, bone, and muscle. Of all the formulas used, the RFM results were the closest to the precise measurements offered from the body scan.

“The relative fat mass formula has now been validated in a large database,” said senior author Richard Bergman, PhD, in a press release. “It is a new index for measuring body fatness that can be easily accessible to health practitioners trying to treat overweight patients who often face serious health consequences like diabetes, high blood pressure, and heart disease.”

The greatest part about the RFM? Because you only need your height and waist circumference measurements, you don’t need to step on the dreaded scale as you would for a BMI. 

RFM Formula

In order to calculate your RFM, all you need to do is plug your height and waist circumference measurements into the formula below. The answer will be your body fat percentage. But what does the number you get actually mean in terms of whether you have a normal weight or not? Experts admit that it’s still a work in progress for the general population. “We still need to test the RFM in longitudinal studies with large populations to identify what ranges of body fat percentage are considered normal or abnormal in relation to serious obesity-related health problems,” said study leader Orison Woolcott, MD.

MEN: 64 — (20 x height/waist circumference in meters) = RFM

WOMEN: 76 — (20 x height/waist circumference in meters) = RFM

In case you’re wondering why the first number is higher for women than it is for men in the RFM formula, that’s simply because women on average have more body fat than men. This is yet another factor that the RFM accounts for, while the BMI essentially ignores.

If you’re concerned about your weight, or the number you get after calculating your RFM, talk to a medical professional about your options. In the meantime, we hope this new RFM method is used in your doctor’s office soon! 

Next, see the tastiest superfoods that can help you live longer in the video below:

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