Body Mass Index

Body Mass Index (BMI) is simply a measure for weight-related health risk.

BMI is one of the measures that your doctor or nurse uses to determine your health risks in relation to your weight. It is a signal to your doctor take a closer look and have a more detailed conversation about your health. The measure is used for adults aged 20 and older and BMI-for-age, also known was BMI percentile is used for children and teens to account for their gender, age, and maturation level.

Specifically, BMI represents the relationship between weight and height to estimate body fatness.¹  A higher percentage of body fat is proven to be associated with increased risk for developing certain diseases such as heart disease, high blood pressure, type 2 diabetes, breathing problems, and certain cancers. 2

What your BMI means:

  • below 18.5 – you're in the underweight range
  • between 18.5 and 24.9 – you're in the healthy weight range
  • between 25 and 29.9 – you're in the overweight range
  • between 30 and 39.9 – you're in the obese range 

How is BMI calculated?

It is as simple as plugging your height and weight into an online calculator, such as the one below.


How is BMI linked to the weight loss journey?

BMI is another tool that can be used to measure success. At the beginning of a weight loss journey, people may find that BMI is useful to tell them where they are starting and provides an initial estimate of their weight-related health risk. The scientific literature suggests that even modest decreases in BMI can significantly improve  health by lowering the risk for high blood pressure, type 2 diabetes, heart disease, obesity-related cancers, and early death.   Additionally, a weight loss of 5-10% has also been associated with improvements in sleep quality, mood, and mobility.  

During the weight loss journey, people tend to find that tracking the change in their weight (either in pounds or kilograms) is more meaningful, and easier to interpret, than changes in BMI.  As with all other indicators of success, BMI is just one measure of success. The goal is not to get to a certain BMI, but to move along the continuum towards a happier, healthier you.


¹ Healthy Weight. (2015, May 15). Retrieved on August 16, 2017 from
James WPT, Jackson-Leach R, Ni Mhurchu C, et al. Chapter 8: Overweight and obesity (high body mass index). In: Ezzati M, Lopez AD, Rodgers A, Murray CJL, eds. Comparative quantification of health risks: Global and regional burden of disease attributable to selected major risk factors. Geneva: World Health Organization. 2004.