BMI, or body mass index, is common knowledge at this point. Just about everyone has looked up their BMI, or their height to weight ratio, to see what it means about their health. In over the years, the idea of BMI has been either hailed as the end-all-be-all for a person’s well-being or as an outdated concept that should be thrown out entirely. There are in fact several other factors at play with any individual that has to be taken into account alongside their BMI. Here are some key facts that you should know about BMI and it’s role in health:
As was teased in the introduction, a person’s weight to height ratio is not the ultimate factor in health. Any healthcare professional worth their salt will also take into account other sources of data, such as waist circumference, or how many inches/centimeters around someone’s waist is, and body fat percentage, or how much body fat a person has in relation to muscle. Waist circumference and body fat percentage, especially concerning the amount of fat located around the internal organs, have both been shown to be more indicative of negative health outcomes than BMI.
There are also often circumstances where these values don’t add up to what is calculated with BMI. For example, an elite athlete could easily have a BMI that would put them in the “overweight” category despite having ideal body fat percentage and waist circumference. Additionally, someone with a perfectly average BMI could have high body fat percentage or waist circumference. These common exceptions have led to an increase in the idea that BMI isn’t a very useful tool at all for determining health, and to an extent studies have shown evidence to back this thought up; BMI values in between the categories of “underweight” (less than 19.9) and “obese” (30 or greater) have similar correlations to health, meaning that there’s actually a large range of values that could therefore be considered “healthy” by this standard.
So while the categories of BMI shouldn’t be used exclusively to determine health, there are certain BMI values that have been shown to significantly increase to risk of severe disease or death, with one study finding that values under 21 or over 30 were the mostly likely to suffer from health issues long term, although waist circumference was considered more of an indicator. Generally, though, reviews of studies have found that values past the “obese” and “underweight” categories are most often when people will begin to have negative health outcomes.
This means that for most people, a slightly high or slightly low BMI doesn’t really affect their overall health, given that their body fat percentage and waist circumference are within normal ranges. Being a bit overweight or below average isn’t in and of itself a reason to panic. Extremes on either side, however, are a different story. A very high or very low BMI alone can often reliably be used as an indicator of current or eventual poor health.
That being said, health is an incredibly complicated topic. There are tons of factors at play, with just a few being genetics, metabolism, and age. Anytime you’re concerned about your health you should see a doctor that assess and treats you for the entire person that you are.