We’ve all heard of BMI, but is it actually a good indication of health?
Measuring your BMI – body mass index – is something you’ve likely had to do. It’s the health test your doctor’s office, your gym, and even your life insurance company might use to help gauge your overall health.
Because of its frequent use, and given that some studies say only about a quarter of adults in the US can call themselves “normal” on the BMI scale, we asked our Studio 5 Health Contributor, Miki Eberhardt, about its reliability.
Find more health advice from Miki on Instagram, @nutritionbymiki.
Is BMI a Scam?
A recent article that ran in the New York Times asked if BMI, or body mass index, is a scam.
There are few single measures in health care that carry as much power as BMI. We run into it not only at doctors’ offices, but also with online calculators, various smart scales, gym assessments, life insurance premiums, and even covid vaccine priority was determined by BMI.
What is BMI?
- It’s a simple height to weight ratio (kg/m2) which gives a number somewhere between 16-40
- Result is defined in a few oversimplified categories:
o < 18.5 underweight
o 18.5-24.9 normal/healthy
o 25-29.9 overweight
o 30+ obese
Many may feel unfairly judged by these numbers (and rightfully so) and in talking to many in the health industry, none claim that the BMI is actually a very useful measure of a person’s health. And in fact, some would even call it a scam.
Where do we see the BMI number being used?
- Various clinics, doctor’s offices, insurance companies, and wellness companies may use this number as a quick way to assess an individual.
- We see it a lot in research since it’s easy and inexpensive to measure, but that doesn’t mean it’s always accurate.
- For example:
o Life insurance companies may charge more for a higher BMI
o Worksite wellness companies may place an employee at greater health risk for a higher BMI… may not get the same incentives as someone with a “normal” BMI
o Doctors may use it as an oversimplified marker to assess overall health or give advice
o And also, I will say from personal experience of doing employee screenings for many years, many people, specifically women, often know this number and know that theirs is “bad” or that they are considered “overweight” or “obese” because this number says they are.
What’s the problem with BMI?
- First, while it may be helpful for large groups of people in research settings, when it comes to assessing an individual, it’s pretty useless.
o Why? It’s only based on height and weight. There is no distinguishing factor that tells us if someone’s weight is higher because they have more muscle or bigger bones. Most athletes who have very little body fat percent would rank as overweight or obese. So, it’s not accurate.
- Second, it was created in the 1830s by a Belgian astronomer meant as a tool for probability at a population level, not ever intended for clinical use or for health assessments.
- Third, it was solely created on the basis of a white, European men. So, it doesn’t account for differences in average body size in other ethnic groups or the entire female population.
- Fourth, it places a skewed value on what is healthy vs what modern-day data tells us.
o Modern-day data shows that the group who would be defined as the “overweight” group with a BMI of 25-30 actually has the lowest mortality risk of any group on the BMI chart. So, there is no reason for anyone to be pushing the lowering of one’s BMI only based on this one number.
Can BMI be harmful?
- It can be.
o If it’s used to set arbitrary goal posts for body size. Someone who is at a healthy, happy weight may feel pressured to continue to lose weight if their BMI is still above 30.
o It also can be harmful if a doctor assumes a person with a normal BMI is healthy and doesn’t probe about potential unhealthy habits they may have.
o Also, if doctors stigmatize overweight patients solely based on BMI, they may miss important diagnoses. There is plenty of evidence that weight stigma is harmful.
What are some tips of things to share if we’re in a situation where we feel BMI is being overvalued?
- Show your knowledge.
o “Based on the history in how BMI came to be, I find it unnecessary for it to be included as part of my health assessment. Are there other markers we could look at instead?”
- Ask not to be weighed or if you feel that your doctor is blaming all symptoms on your weight, I would ask:
o “Is this the same advice you would give to someone who is at a normal BMI or normal weight?”
So, if BMI isn’t important to monitor for health, what is?
- Waist Circumference. For women, a good guideline is around 35 inches or less at the smallest part of your waist.
- Other metabolic markers like glucose, triglycerides, HDL, and blood pressure.
- Also, if you’re seeking better health, prioritize behaviors that are more within your control than your BMI: better sleep, more movement, managing stress, an abundance of fruit and veggies
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