By Vallari Kothari, MD, Griffin Faculty Physicians Endocrinologist
Body Mass Index (BMI) is a measure of weight in relation to height. It is an inexpensive, easy and practical method to determine if you are underweight, at a healthy weight, overweight, or obese.
BMI is an estimate of body fat and an indicator of your risk for diseases that can occur with more body fat. The higher your BMI, the higher your risk for certain diseases such as type 2 diabetes, high blood pressure, heart disease, stroke, gallstones, high LDL (bad) cholesterol, low HDL (good) cholesterol, sleep apnea & breathing problems, certain cancers (endometrial, breast, colon, kidney, gallbladder, and liver), depression, osteoarthritis, and all-causes of death (mortality).
BMI is calculated by dividing a person’s weight in kilograms by the square of height in meters. BMI = weight (kg) / [height (m) x height (m)].
Click here for an online BMI calculator on the Griffin Bariatrics website (the calculator is located on the right-hand side of the webpage).
Weight Categories
The standard weight categories associated with BMI ranges for adults more than 20 years is:
| BMI | Weight categories |
| <18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30 and above | Obese |
BMI Categories for Children
BMI for children and teens (2-19 years) is calculated using the same formula as adult BMI but it is interpreted differently. BMI growth charts consider age and sex specific differences and visually show BMI as a percentile ranking.
| BMI percentile for age and sex | Weight categories |
| <5th percentile | Underweight |
| 5th – 84th percentile | Healthy weight |
| 85th – 94th percentile | Overweight |
| 95th percentile and above | Obese |
Limitations of BMI
As weight of an individual is fat mass, plus lean body mass (muscle and bone), the limitation of BMI is that it overestimates body fat in athletes and others who have a muscular build, and underestimates body fat in elderly and others who have lost muscle. With that said, the accuracy of BMI as an indicator of body fatness also appears to be higher in people with higher levels of BMI.
A healthcare provider is able to properly assess and evaluate an individual’s BMI, health status, risks, and recommend how much weight one might need to lose. The good news is that weight loss of even 5-10% of your current weight will help lower your risk of developing diseases associated with obesity. If you are concerned with your weight, BMI, or obesity related diseases like type 2 diabetes, contact your Griffin Faculty Physicians Endocrinologist for an appointment at (203) 735-3500.
References:
2013 AHA/ACC/TOS Guideline for the Management of Overweight and Obesity in Adults.
Garrow, J.S. & Webster, J., 1985. Quetelet’s index (W/H2) as a measure of fatness. Int. J. Obes., 9(2), pp.147-153.
Flegal, K.M. & Graubard, B.I., 2009. Estimates of excess deaths associated with body mass index and other anthropometric variables. Am. J. Clin. Nutr., 89(4): 1213–1219.
Willett, K. et al., 2006. Comparison of bioelectrical impedance and BMI in predicting obesity-related medical conditions. Obes. (Silver Spring), 14(3), pp.480–490.
Kuczmarski, R.J. et al., 2002. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat. 11., 11(246), pp. 1-190.
Bhaskaran K, Douglas I, Forbes H, dos-Santos-Silva I, Leon DA, Smeeth L. Body-mass index and risk of 22 specific cancers: a population-based cohort study of 5.24 million UK adults. Lancet. 2014 Aug 30;384(9945):755-65.