BMI stands for body mass index. It’s used by doctors because it helps us measure the proportionality of a person’s height and weight. For example, it wouldn’t be fair to say someone who is 6 feet tall should weigh as much as someone who is 5 feet tall. BMI makes it so we can see if someone weighs a healthy amount for their height. But what is “healthy?” 

The medical community has set some standards as to what BMIs are a healthy weight, what BMIs are under- or overweight, and what BMIs are considered obese. On the surface, BMI is a tool. However, it’s also cold, impersonal and does not measure the overall health of an individual. Health is actually determined by a number of factors. The nutrients we put into our bodies, if we are physically active, how much sleep we get at night and our mental wellness all contribute to our overall health.

At the end of the day, BMI is just a number.

That said, we know for certain that there are a few types of unhealthy BMIs: ones that change too quickly, ones that are too low and ones that are too high. Any of these might suggest that something else is going on in the body. The body suffers when it’s caloric input changes drastically (something that can happen with crash dieting, mental distress or cancer), which can be seen with a rapid change in BMI. The body also suffers when it does not have enough nutrients to grow and replenish itself (as can happen if BMI is too low) or when it can't keep up with processing foods that can cause damage (as can happen if BMI is too high).

I’ve not put any numbers here because the number itself shouldn’t be the focus. (If you are interested in calculating your number you can look in the tools section.) But try to remember that your body is at its best when your BMI remains steady due to a healthy lifestyle and mental wellness. That's what matters.