What You Need to Know About Your BMI (Body Mass Index)

What You Need to Know About Your BMI (Body Mass Index)


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What is BMI (Body Mass Index)?

Body Mass Index (BMI) is the recommended method for diagnosing if you are overweight or obese. It is a calculation based on your height and weight, which determines if you are the appropriate weight to minimize risk for developing excess weight-related diseases, such as diabetes, cardiovascular disease, joint pain, high blood pressure, sleep apnea, and others.

Body Mass Index is an imperfect but important tool to aid in diagnosing obesity and risk for disease, so most doctors use it as one piece of a puzzle to determine the health of an individual. The BMI was developed to identify people with excess body fat, but it does not take into consideration the other components of the body: bone, water, and muscle.

What is an Unhealthy BMI?

Medical guidelines dictate (and most practitioners agree) that a BMI of 25 or above is too high, and therefore unhealthy. BMI numbers between 25 and 29.9 are considered "overweight" and BMIs 30 or higher are considered "obese". BMIs above 25 have been shown to increase the risk of developing high blood pressure, heart disease, stroke, diabetes, certain types of cancer, arthritis, and breathing problems1-5.

What is a Healthy BMI?

The healthy range for BMI is considered to be between 18 and 24.9. While you may think that the lower your BMI is, the better, a person with a BMI below 18 is actually considered underweight.

How to Calculate Your BMI

Calculating your BMI can achieved manually, using the calculation below, or there are several online BMI calculators available (links below to 2 online calculators). Here is the mathematical equation to calculate your BMI:

BMI Calculator

705 X Body weight (in pounds) ÷ (Height (inches) X Height (inches)

So, for example: a person who is 6 feet tall (72 inches) and weighs 200 pounds has a BMI of 27. Here's the process using the calculation above: 705 X 200 = 141,000 ÷ 5184 = 27 (rounded).

Here are links to online BMI calculators:

National Institutes of Health BMI

Centers for Disease Control BMI Calculator

1 Hubert HB, Feinleib M., McNamara PM, Castelli WP. Obesity as an independent risk factor for cardiovascular disease: a 26 year followup of participants in the Framingham Heart Study: Circulation. 1983; 67:968-977.

2 Walker SP, Rimm EB, Ascherio A, Kawachi I, Stampfer MJ, Willett WC. Body size and fat distribution as predictors of stroke among US men. Am J Epidemiol 1996;144; 1143-1150.

3 Colditz GA, Willet WC, Rotnitzky A, Manson JE. Weight gain as a risk factor for clinical diabetes mellitus in women. Ann Intern Med,. 1995:122:481-486.

4 Giocannucci E, Ascherio A, Rimm EB, Colditz GA, Stampfer MJ, Willet WC. Physical activity, obesity, and risk for colon cancer and adenoma in men. Ann Intern Med. 1995;122:327-334.

5 Hochberg MC, Lethbridge-Cejku M, Scott WW Jr., Reichle R, Plato CC, Tobin JD. The association of body weight, body fatness and body fat distribution with osteoarthritis of the knee: data from the Baltimore Longitudinal Study of Aging. J Rheumatol 1995;22:488-493.

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