weight and assessing disease risk

Medical evidence shows that people who are overweight or obese have a greater chance of developing high blood pressure, high blood cholesterol or other lipid disorders, type 2 diabetes, heart disease, stroke, and certain cancers. Disease risk due to overweight can be assessed using three key measures:

Body mass index (BMI)
Waist circumference
Additional risk factors

BMI is a measure of weight relative to height. Waist circumference measures abdominal fat. Combining these measures with information about the patient's health status (existing diseases such as coronary heart disease, type 2 diabetes, sleep apnea or additional risk factors) yields an estimated risk for developing obesity-associated diseases. Body Mass Index (BMI) BMI is a suitable tool for assessing total body fat in most adults. Although it is not suitable for patients who are highly muscular or who have edema, it can be effectively used for assessing most others. BMI is assessed as follows:

< 18.5: Underweight
18.5 - 24.9 : Normal
25.0 - 29.9 : Overweight
> 30: Obese

To measure BMI, multiply weight in pounds by 703, and then divide that number by height in inches squared. For example, to calculate the BMI of a six-foot tall person weighing 217 pounds, use the following calculation.

(217 x 703)/(72 x 72)= 29.4 BMI

Waist Circumference
Waist circumference measures abdominal fat. A high waist circumference can be a marker for increased risk even in persons of normal weight. Men with waist circumferences greater than 40 inches, and women with waist circumferences greater than 35 inches are considered to be at higher risk for diseases associated with overweight and obesity, regardless of their BMI.

Assessment of Risk Status
When assessing a person's disease risk, information regarding the patient's health status including existing coronary disease or other atherosclerotic diseases, type 2 diabetes, sleep apnea or additional risk factors should be considered. These risk factors include: age (Men >45 years; Women > 55 years), high blood pressure, high LDL-cholesterol ("bad cholesterol), low HDL-cholesterol ("good cholesterol"), high triglycerides, high blood glucose (sugar), family history of premature heart disease, physical inactivity, and cigarette smoking. People with two or more risk factors are considered at a higher risk for obesity-related diseases, regardless of their BMI or weight circumference.

Who Should Lose Weight?
People who have a BMI greater than or equal to 30, AND those who have a BMI of 25 to 29.9 OR a high waist circumference with two or more risk factors should lose weight. Even a small weight loss (just 10 percent of your current weight) will help to lower your risk of developing diseases associated with obesity. Individuals who are overweight, do not have a high waist measurement, and have less than two risk factors may need to prevent further weight gain rather than lose weight.

Sources For More Information

The above information is based on a 228-page NHLBI Expert Panel report, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: The Evidence Report, which provides the most thorough examination of the scientific evidence available to date for treating overweight and obesity.

Print versions of most materials can also be ordered from NHLBI's Online Catalog at http://emall.nhlbihin.net, or the NHLBI Information Center by telephone: 301-592-8573 or fax: 301-592-8563.

September 1998