Heart disease, diabetes and high blood pressure are all linked to being overweight. A BMI of 30 and over increases the risk of death from any cause by 50 to 150 percent, according to some estimates. According to health experts, people who are overweight but have no other health risk factors (such as high cholesterol or high blood pressure) should eat healthier and exercise to keep from gaining additional weight. For people who are overweight and also have health risks, they recommend trying to actively lose weight. Be sure to consult your doctor or other health professional before beginning any exercise or weight-loss program.

    The current guidelines now have a new definition of a healthy weight -- a BMI of 24 or less. So now a BMI of 25 to 29.9 is considered overweight. Individuals who fall into the BMI range of 25 to 34.9, and have a waist size of over 40 inches for men and 35 inches for women, are considered to be at especially high risk for health problems.

Body Mass Index (BMI)

Risk of Associated Disease According to BMI and Waist Size
BMI		Waist less than or equal to 40 in. (men) or 35 in. (women)	Waist greater than 40 in. (men) or 35 in. (women)
18.5 or less	Underweight	--	N/A
18.5 - 24.9	Normal	--	N/A
25.0 - 29.9	Overweight	Increased	High
30.0 - 34.9	Obese	High	Very High
35.0 - 39.9	Obese	Very High	Very High
40 or greater	Extremely Obese	Extremely High	Extremely High

 

Both Body Mass Index (BMI) and Waist Circumference (WC) can be useful measures of determining obesity and increased risk for various diseases. According to the National Institutes of Health, a high WC is associated with an increased risk for type 2 diabetes, dyslipidemia, hypertension and cardiovascular disease when BMI is between 25 and 34.9. (A BMI greater than 25 is considered overweight and a BMI greater than 30 is considered obese.) WC can be useful for those people categorized as normal or overweight in terms of BMI. (For example, an athlete with increased muscle mass may have a BMI greater than 25 - making him or her overweight on the BMI scale - but a WC measurement would most likely indicate that he or she is, in fact, not overweight). Changes in WC over time can indicated an increase or decrease in abdominal fat. Increased abdominal fat is associated with an increased risk of heart disease.

(BMI for Children and Teens is sometimes referred to as "BMI-for-age.")

BMI is Used Differently with Children Than it is With Adults

In children and teens, body mass index is used to assess underweight, overweight, and risk for overweight. Children's body fatness changes over the years as they grow. Also, girls and boys differ in their body fatness as they mature. This is why BMI for children, also referred to as BMI-for-age, is gender and age specific.^{1, 2} BMI-for-age is plotted on gender specific growth charts. These charts are used for children and teens 2 – 20 years of age. For the 2000 CDC Growth Charts and Additional Information visit CDC's National Center for Health Statistics.

Each of the CDC BMI-for-age gender specific charts contains a series of curved lines indicating specific percentiles. Healthcare professionals use the following established percentile cutoff points to identify underweight and overweight in children.

Example
Let's look at the BMI for a boy as he grows. While his BMI changes, he remains at the 95th percentile BMI-for-age.

We see how the boy's BMI declines during his preschool years and increases as he gets older.

Why is BMI-for-age a useful tool?
BMI-for-Age is used for children and teens because of their rate of growth and development. It is a useful tool because

• BMI-for-age provides a reference for adolescents that can be used beyond puberty.
• BMI-for-age in children and adolescents compares well to laboratory measures of body fat.
• BMI-for-age can be used to track body size throughout life.

For the 2000 CDC Growth Charts and Additional Information visit CDC'S National Center for Health Statistics.

For more information on how to use the growth charts visit The Growth Chart Training Modules.