The Truth About BMI in Under 5 Minutes

With special guest registered dietitian and sports nutritionist, Marilyn Gordon

I can vividly remember the first time I heard the acronym “BMI”. I was probably 10 or 11 years old. I was getting my yearly check-up and toward the end of the appointment, my pediatrician suggested that I maybe start reading my books while on a treadmill every now and then because I was climbing “the BMI chart.” Now, before anyone gets offended, let me say I saw the same pediatrician from the age of 6 months to 21. And I loooooved my pediatrician. So he knew me well, and knew how to get through to me. I was the completely nerdy kid who LOVED reading Nancy Drew and Baby Sitters’ Club and GirlTalk books (does anyone remember GirlTalk books?). Anyway, so began my obsession with the BMI chart. Or really, my loathing of it.

One of the greatest feelings that has come along with the FASTer Way to Fat Loss is the unchaining I’ve felt from both the scale and that blasted BMI chart. So what is BMI, exactly. “Body mass index, or BMI, is a measure of body size. It combines a person’s weight with their height.”¹ As such, it’s been a tool for years and years to determine if someone is an appropriate weight for his/her height.

Now, as a doctor’s wife (especially a sports medicine physician), I have the advantage of having ridiculously easy access to SO many useful resources: doctors, psychologists, physical therapists, etc. In this instance, I wanted someone who looks at BMI all day: a registered dietitian. So I asked registered dietitian and sports nutritionist, Marilyn Gordon, to weigh in on BMI. Marilyn has A LOT of letters behind her name (EdD, RDN, CSSN, and LDN), so you don’t have to worry. She knows what she’s talking about. Here’s what Marilyn has to say:

“Everything you wanted to know about Body Mass Index (BMI) can be found here.

As a Registered Dietitian and Licensed Nutritionist, I recognize that BMI is just a screening tool and only one piece of a larger health and fitness portfolio. While BMI has many limitations, it can identify individuals who are at risk for health conditions exacerbated by excess body fat and weight such as cardiovascular disease, diabetes, orthopedic injury, digestive and reproductive systems. I work primarily with the athletic population so BMI is not as useful due to the athletes’ high percentage of lean body mass (muscle). Often the athlete may have a BMI of 28 (classifying them as overweight), however if you give further evaluation of body composition using the BodPod, Ultrasound, Dexa scan, or skinfold calipers, you will see that a good portion of the “weight” is actually muscle—a result of strength training and good nutrition.

If body fat reduction is your goal, do not rely solely on BMI; as you become stronger and fit, the BMI might increase, however at the same time your clothes are fitting better and you are receiving compliments from your friends and family.” (Thanks, Marilyn!)

I wanted to make sure y’all caught that last part. If you’re living the FASTer Way to Fat Loss life, fat loss is what our goal is… building fat burning muscle. So our weight, and consequently BMI, might not fit perfectly within the parameters of the BMI chart. If you’re worried about not fitting on that curve, ask your doctor to measure your actual body fat percentage. By monitoring your body fat percentage, you’ll see how much fat your losing AND how much muscle you’re building.

So, what’s the moral of the story? The scale and the BMI chart CANNOT tell the whole story of your journey. You might weigh the same two months in a row, but your body composition could be completely changing. So don’t fret!

1. Measuring BMI for adults, children, teens-

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