When you visit the doctor’s office there is a good chance you will hear about BMI. At the least, you will see your designated number and category on the visit summary. What does it mean and what is the application today?

Body mass index (BMI) is a screening tool to identify weight categories and potential health risks. BMI is calculated using weight in kilograms over height in meters squared. It was invented in the 1800s and became a health standard in the 1980s. It’s use has developed over time in attempt to target and treat the obesity epidemic. However, there are flaws to this measurement. And are there better tools out there?

BMI	Weight Category
<18.5	Underweight
18.5-24.9	Normal
25-29.9	Overweight
>30	Obese

Flaws (what BMI does not consider):

1. Muscle Mass vs Fat Content– for example: a body builder with a BMI of 30 and fat content of 7% is classified as obese. Or a lean athlete with a BMI of 26 is classified as overweight. Or an overweight, sedentary individual with a BMI of 26. A classic comparison of apples to oranges.
2. Age– a healthy weight is likely different for a 21 year old vs a 41 year old
3. Gender– fat content and distribution differs in male and female
4. Physical Activity– exercise decreases risk of many disease states
5. Genetics– the factor we have no control over can play a big role in health risks and outcomes

Other Tools:

Waist to Hip Ratio (WHR)– there is new data out to support the use of this tool. It better identifies individuals with higher fat percentages, particularly in the waist (visceral fat, which is high risk). A recent study found that it is a greater predictor of heart disease and mortality. It is a simple calculation of waist circumference divided by hip circumference. A value of 1 or greater is considered at risk for certain health conditions.

Waist Circumference– one measurement which targets visceral fat. Studies have found that a waist circumference of >35 inches in females and >40 inches in males significantly increases risk for the development of heart disease, diabetes, and liver disease.

So why are we still using a flawed system?

Well, it’s easy! All you need is height and weight. Additionally, it has been around a long time. BMI can serve as a guide for most but shouldn’t be followed to an extreme. Consider other things like muscle mass, age, gender, fat distribution, physical activity, and genetics. Tools such as WHR and waist circumference may be better indicators of health risks. Continue to watch for the development of new tools and application in the near future!

As always, reach out with questions, comments, and for further discussion.

Lindsey, PharmD, BCPS