Is BMI Biased Against Blacks & Women? 2 Pitfalls of a Health Metric

On a long car ride back into NYC, I got into a heated debate with my brother -who happens to be a doctor- about the usefulness of the “Body Mass Index” (BMI) for black people. From his (medical) point of view, BMI is necessary because it’s a cheap & clear way to know if someone is at risk for weight-related illnesses. But are there certain groups, namely women & people of color, who disproportionately lose out when we rely on BMI?

What is the Body Mass Index?
BMI is an index that slots you into either the normal weight/overweight/obese categories. It’s used to screen for obesity-related illnesses like hypertension, type 2 diabetes and heart disease [1]. BMI is also being used by employers as an eligibility requirement for hiring [2] and even as a metric for determining health benefits [3]! Check out the chart below to get a sense of your BMI or click here.

Is BMI Biased?
BMI has long been criticized as a limited health metric.[4][5][6] Because your BMI takes your entire weight into account, it can’t account for the good stuff (eg. muscle, bone mass) or how bad stuff, like body fat, is distributed. Here’s why I’d argue that BMI is especially limited when it comes to measuring the health of women and people of color:

1. Women tend to carry more body fat than men.
Women’s bodies carry more fat than men because of our biology. A healthy body fat percentage in women can range between 15-25% while the healthy range for men is only 10-15%. [7] Women’s bodies also produce estrogen, which may contribute to increased storage of body fat [8]. The BMI chart does not account for this however; one chart is used for both men and women. This means that women are more likely to be skewed farther down the BMI range.

2. Studies suggest there may be higher bone density and lean muscle mass in African-Americans, which can inflate BMI calculations. [9][10]
In study published by the British Journal of Nutrition, researchers found that in a group of Blacks, Latinos, Asians and Whites with the same BMI, blacks had a lower body fat percentage than their white, latino and asian counterparts. This may suggest that other factors besides body fat can over-inflate the BMIs of black people when tested.

So What Should You Do?

Omron BF306. Body fat monitor for the upper bo...

1. Don’t completely ignore BMI.
If you’ve got a BMI of over 30 or under 18.5, you’re probably in trouble health-wise. Talk to your doctor about what you can do to get your health back on track. If you’re on the margins of one of the ranges (normal/overweight/obese), you should treat your BMI as a general guidepost and work from there (see #2 below).

2. Use multiple metrics to get a clearer sense of your health.
If your doctor tells you that you need to lose weight, ask him/her what that determination is based on. If they say it’s based on BMI and you figure out that you’re on the BMI margins for overweight/obese, ask your doctor for more information! A body fat percentage test using the hand-held device (pictured above) or a calipers test could give a clearer picture. And also be sure to have your blood work done to test for your cholesterol and triglyceride levels!

3. Exercise more and eat clean.
Need I say more on this one? You already know what blog you’re on. ;-)

-CFC

***Do you ignore your BMI? Why or why not? Do you think it’s best to have ONE clear metric for everyone or should health tests take gender/race differences into account? Sound off!!***

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About ChicFitChef

My "deserted island" checklist: a BCBG dress, a healthy & diabetic-friendly meal and a few workout DVDs. ;-)
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11 Responses to Is BMI Biased Against Blacks & Women? 2 Pitfalls of a Health Metric

  1. Oortaq says:

    I think it’s an important metric, but it’s just not realistic for many people and body types. Case in point–me. When I told my bariatric surgeon that I wanted to be 150 (the cut off for “normal” on the BMI for my height), he started to laugh. Not hard, like a chuckle. Why? He said from my lifetime of being overweight I literally have heavy/thick bones. Further, my body frame is at least medium if not large (I’ve got shoulders like football player). He definitely thought 165, but 150 in his opinion would leave me starving myself. He wasn’t the only one–I had two primary care doctors and a nutritionist tell me essentially the same thing. People’s bodies are different. The BMI isn’t the end-all, be-all. It’s a metric–if you’re able to run, lift, etc. and you’re over the cut off, then it’s about accepting who you are and your size. Just my thoughts, but I’m not a doctor.

    • ChicFitChef says:

      Agreed! I definitely think that the metric is limited- there are so many body types out there…I guess my brother (and I’m sure the medical community’s) point is just that they need something as a baseline…I think body fat percentage should be the new starting point though not BMI.

  2. The Doc Is In says:

    Great post, totally agree. BMI is certainly better than nothing but it a lot of situations % body fat is a much better predictor of metabolic disease, etc. I’m certainly not anyone’s perfect size but I am (thank God) healthy and consider myself pretty fit. People are always surprised to hear my actual weight…my BMI is actually right at the border of healthy/overweight. The “ideal body weight” marker is even worse, I’m 20 lbs over that one o_O. We have people focused solely on getting numbers on the scale down when increased lean muscle mass and bone density are also incredibly important for overall health and not taken into account with these markers.

  3. BMI is not a valid way to assess health. It does not take muscle into account at all, which means that a bodybuilder with almost no body fat can be considered “overweight”, as can many athletes who have a lot of muscle but little fat. BMI can not differentiate between the 6’2″ 240lb man who is fat and the 6’2″ 240lb bodybuilder. I think that measuring body fat percentage is a better way to gauge if you need to loose weight than BMI is. Some people love to preach BMI, but it is an antiquated way to assess health.

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