What is a Healthy BMI?

August 27, 2015

In addition to providing with the most accurate weight measurements, the Withings Wireless Scale also calculates your Body Mass Index (BMI). Here’s what you should know about this key health indicator.

Who invented the Body Mass Index and how is it calculated?

The BMI was established by Belgian astronomer, mathematician, statistician and sociologist Adolphe Quetelet in the first half of the 19th century.
Your BMI is an equation mixing your height and your weight and the result is intended to assess if you have a healthy weight/height ratio.
The BMI formula:
BMI = weight / height2

What is a healthy BMI?

Based on Quetelet’s work, the World Health Organization (WHO) defined The International Classification of adults who are underweight, overweight and obese:

  • BMI under 18.5: Underweight
  • BMI from 18.5 to 24.9: Normal weight
  • BMI from 25 to 29.5: Overweight
  • BMI over 30: Obese

Note: If you are a top level athlete or a weight-lifter, the general BMI model isn’t going to be as accurate. We advise you to switch your body composition model to “Athlete” in the Health Mate app.

What are the risks for my health if I’m not in the “Normal” weight category?

On the one hand, people with a BMI higher than 25 have a higher risk of developing heart disease, hypertension, stroke and diabetes. On the other hand, a BMI lower than 18.5 may indicate an eating disorder or malnutrition.
Body Mass Index Isn’t Perfect
Many people have raised issues with BMI calculations. Some of these issues include a criticism that Body Mass Index ignores factors like the scaling of height, the fact that it can’t differentiate fat mass from muscle mass and exactly where the line for overweight and obese should be set.
That said, Quetelet’s system has survived for generations, largely unchanged, and is still considered one of the best tools to help classify and assess the health of individuals and the general population.
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Photo credit (top): Thank you to Adrian Pelletier and his Nature Stock site


At Withings, we make a range of products that empower people to make the right decisions for their health. Our award-winning connected devices are known for personalization, cutting-edge design, and ease of use, allowing anyone to measure, monitor, and track what matters via seamless connection to the free Health Mate app available for iOS & Android.
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