BMI and PCOS: Useful or Useless?

Body mass index (BMI) has been around for decades as a tool to determine if someone is at a healthy weight or not, but is it useful or appropriate for women with polycystic ovary syndrome (PCOS)? We weigh in.

What is BMI?

BMI was originally established nearly 200 years ago by a mathematician to give the government a quick way to determine if someone was obese (yes, fat phobia even existed back then). It is now used by the medical community and government as a way to determine weight status.

BMI is calculated by dividing someone’s weight (in kilograms), by their height (in meters), and dividing the answer by height again.

A BMI below 18.5 is regarded as ‘underweight’

A BMI between 18.5 and 24.9 is considered ‘normal weight’

25 or over is ‘overweight’

30 or more is categorized as ‘obese’

A BMI over 40 indicates extreme obesity

How Accurate Is BMI?

A big flaw with BMI is that it doesn’t take into account muscle mass or water or bone density. It doesn’t tell you what type or amount of body fat a person has. BMI also doesn’t measure exercise, diet, or blood results to indicate health, nor does it take age or ethnicity into consideration. Certainly not all women who are 5’5” and weigh 125# are built the same or have the same health.

A study published in the International Journal of Obesity showed that nearly half of people diagnosed as obese using BMI measurements are actually healthy, leading some to believe that there is no value of a BMI measurement at all, except for life insurance policies to increase premiums.

What Does BMI Mean for Women with PCOS?

Despite the fact that BMI is not a reliable indicator of health, doctors still urge patients to get their BMI into the ‘healthy weight’ category. Some fertility doctors won’t even consider doing IVF treatment unless a woman has a BMI under 40, or require her to have a BMI of less than 44 before initiating IUI cycles.

Women with PCOS can build muscle quicker and perhaps easier than those without the condition due to high testosterone levels (the one good thing about PCOS!). This can affect BMI. Many professional athletes in fact are labeled as obese. Are they unhealthy then?

A number, whether it be BMI or on a scale, is only that: a number. It doesn’t indicate health. Yes, women with PCOS can be fat (or overweight, of size, plus-size, or however you prefer to call it, and still be healthy if they take care of themselves.

Instead of focusing on numbers, we recommend focusing on healthy behaviors like feeding your body with whole foods, taking supplements to help regulate hormones and to help improve metabolic parameters, getting regular physical activity and sufficient sleep, practicing mindfulness, and enjoying life.

What has your experience been with BMI and the medical community? Share your thoughts with us below.

Tomiyama AJ1, Hunger JM2, Nguyen-Cuu J1, Wells C3.Misclassification of cardiometabolic health when using body mass index categories in NHANES 2005-2012. Int J Obes (Lond). 2016 May;40(5):883-6.

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Comments (4)

    February 24, 2017 at 2:49 am

    Reading this article has triggered emotions of anger, frustration, happiness and relief.
    Because of my BMI we are unable to qualify for IVF treatment on the NHS. My BMI is 33 however I am healthy, I exercise regulary, have lost 2 dress sizes for the last 1 year and despite this the number on the scale had not moved much. I have more muscle mass and my cycle have become regular since started taking inositol 6 months ago. I am 39 and losing hope for a free IVF treatment because the medical professionals only look at the BMI and not at the person, the condition PCOS and its link to the difficulties of losing weight. They don’t consider the efforts you make to be healthy. It makes me feel so frustrated and infuriated! Thank you for publishing this article. It feel like someone is finally on my side.

  • Ebony

    July 19, 2017 at 9:02 am

    My BMI is 28.7 but I am a US size 4 on top and 6-8 on the bottom. Doctors telling me I’m too fat have me an eating disorder. If I am this size at this weight, you can imagine how skeletal I was when I starved myself down to a ‘normal weight’ at BMI 18.9.

  • Hilo

    December 12, 2019 at 8:16 pm

    Back in high school, our P.E. class took BMI’s and I learned how “overweight” I was. Within a year and a half, I lost nearly 50 lbs and was submitted into a hospital to account for a slow heart beat. I discovered I was anorexic and going through treatment for a year before my family could no longer afford to pay for it. Today, I have gained much of my weight back and a bit more, yet eating can be a struggle. Reading this article was pretty nerve racking for me but I appreciated the article’s shift from numbers to overall wellbeing. Thank you for sharing this! I wish these were concepts shared with me over my education system’s emphasis in numbers.

  • Lashawnna

    December 28, 2020 at 5:42 pm

    Hi I’m 31 years old and was Diagnosed with PCOS at the age of 18 I had my First miscarriage at 23 years old One successful pregnancy and delivery and in 2018 I had another miscarriage I am trying to have another child for the most part my periods are very normal as far as I get them every month the length of them are 34 days I’m 5’10 228 lbs what are some tips for dropping some pounds

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