In: Hu F, ed. Obesity Epidemiology. New York City: Oxford University Press, ; 53— Skip to content Obesity Prevention Source. Obesity Prevention Source Menu. Search for:. Home Obesity Definition Why Use BMI? Waist Size Matters Measuring Obesity Obesity Trends Child Obesity Adult Obesity Obesity Consequences Health Risks Economic Costs Obesity Causes Genes Are Not Destiny Prenatal and Early Life Influences Food and Diet Physical Activity Sleep Toxic Food Environment Environmental Barriers to Activity Globalization Obesity Prevention Strategies Families Early Child Care Schools Health Care Worksites Healthy Food Environment Healthy Activity Environment Healthy Weight Checklist Resources and Links About Us Contact Us.

The most basic method, and the most common, is the body mass index BMI. Doctors can easily calculate BMI from the heights and weights they gather at each checkup; BMI tables and online calculators also make it easy for individuals to determine their own BMIs.

Strengths Easy to measure Inexpensive Standardized cutoff points for overweight and obesity: Normal weight is a BMI between The correlation between the BMI number and body fatness is fairly strong; however the correlation varies by sex, race, and age.

These variations include the following examples:. It is also important to remember that BMI is only one factor related to risk for disease. Measuring waist circumference helps screen for possible health risks that come with overweight and obesity. This risk goes up with a waist size that is greater than 35 inches for women or greater than 40 inches for men.

To correctly measure your waist, stand and place a tape measure around your middle, just above your hipbones. Measure your waist just after you breathe out. Although the BMI number is calculated the same way for children and adults, the criteria used to interpret the meaning of the BMI number for children and teens are different from those used for adults.

For children and teens, BMI age- and sex-specific percentiles are used for two reasons:. Because of these factors, the interpretation of BMI is both age- and sex-specific for children and teens. For adults, on the other hand, BMI is interpreted through categories that are not dependent on sex or age.

Search site Search Search. Go back to previous article. Sign in. How is BMI used? Other methods for Assessing Body Composition Other methods to measure body fatness include skinfold thickness measurements with calipers , underwater weighing, bioelectrical impedance, and dual-energy x-ray absorptiometry DEXA.

Other methods for Assessing Body Composition Calculating BMI BMI is calculated the same way for both adults and children. The information and materials contained on this website are not intended to constitute a comprehensive guide concerning all aspects of the therapy, product or treatment described on the website.

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Summary Read the full fact sheet. On this page. What is a healthy BMI range for children? Being overweight or underweight can affect your health Risks of being overweight high BMI and physically inactive Risks of being underweight low BMI Waist circumference is a better indicator of increased disease risk Waist circumference and health risks Where to get help.

Eat for health: Australian dietary guidelines summary External Link , National Health and Medical Research Council, Australian Government. About child and teen BMI External Link , US Centers for Disease Control and Prevention.

Mooney SJ, Baecker A, Rundle AG , ' Comparison of anthropometric and body composition measures as predictors of components of the metabolic syndrome in a clinical setting External Link ', Obesity Research and Clinical Practice, vol 7, no.

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It is calculated from your height and weight. BMI is an estimate of body fat and a good gauge 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 heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers. Although BMI can be used for most men and women, it does have some limits:.

Use the BMI Calculator or BMI Tables to estimate your body fat. The BMI score means the following:. Measuring waist circumference helps screen for possible health risks that come with overweight and obesity. This risk goes up with a waist size that is greater than 35 inches for women or greater than 40 inches for men.

To correctly measure your waist, stand and place a tape measure around your middle, just above your hipbones. Measure your waist just after you breathe out. The table Risks of Obesity-Associated Diseases by BMI and Waist Circumference provides you with an idea of whether your BMI combined with your waist circumference increases your risk for developing obesity-associated diseases or conditions.

Along with being overweight or obese, the following conditions will put you at greater risk for heart disease and other conditions:. For people who are considered obese BMI greater than or equal to 30 or those who are overweight BMI of 25 to Even a small weight loss between 5 and 10 percent of your current weight will help lower your risk of developing diseases associated with obesity.

People who are overweight, do not have a high waist measurement, and have fewer than two risk factors may need to prevent further weight gain rather than lose weight. Talk to your doctor to see whether you are at an increased risk and whether you should lose weight.

Your doctor will evaluate your BMI, waist measurement, and other risk factors for heart disease. The good news is even a small weight loss between 5 and 10 percent of your current weight will help lower your risk of developing those diseases.

The BMI Calculator is an easy-to-use online tool to help you estimate body fat. The higher your BMI, the higher your risk of obesity-related disease. Health Topics The Science Grants and Training News and Events About NHLBI.

These tools are not exact, and not everyone with excess weight will develop health issues. However, some researchers believe people with obesity who have no other health conditions are still at increased risk for developing obesity-linked conditions, such as metabolic syndrome and cardiovascular disease in the long term.

People who want to learn more about their current health status, future risks, and ways to improve health can benefit from speaking with their doctor. A BMI calculation provides a single number, which the Centers for Disease Control and Prevention CDC categorizes as follows:.

It is a screening tool that people should use alongside other tests and assessments to determine potential health risks. A person can talk with their doctor if they have questions about calculating or interpreting their BMI score.

Age is not a factor in BMI for adults, but it is for children. This is because children typically grow larger with age. The CDC use both age and sex assigned at birth in its BMI calculations for people between the ages of 2—19 years. BMI is a very basic measurement.

While it takes height and weight into consideration, it does not account for factors such as:. These factors can affect health. For example, high performance athletes tend have a lot of muscle and little body fat. They can have a high BMI because they have more muscle mass, but this does not mean they weigh too much for their height.

Another limitation of BMI is that it does not distinguish between people of different racial or ethnic groups. Studies have shown that non-Hispanic white, non-Hispanic Black, and Mexican Americans may have significantly different levels of body fat but the same BMI as people from other groups.

This inaccuracy may lead to a misdiagnosis or an incorrect assessment of risk factors between individuals. BMI can offer a rough idea of whether or not a person is at a moderate weight, and it is useful for measuring trends in population studies.

However, it should not be the only measure an individual uses to assess whether their weight is ideal. Learn more about the limitations of BMI. A high WHR is has associations with higher levels of visceral fat , the fat in the abdominal cavity that surrounds several major organs.

For this reason, the WHR can be a useful tool for understanding potential health risks when considered alongside other assessments of health status. A meta-analysis suggests that having a high WHR can put people at a higher risk of myocardial infarction, or heart attack.

To calculate their WHR, a person should measure around their waist at the narrowest part, usually just above the belly button.

They can then divide this measurement by the width of their hip at its widest part. Using WHR, a World Health Organization WHO report defines abdominal obesity as follows:.

However, as with BMI, the WHR does have limitations. Optimal WHR differs based on sex assigned at birth as well as race and ethnicity, according to the WHO report.

Plus, body size is not a direct measure of health. To discover more evidence-based information and resources for weight management, visit our dedicated hub. The waist-to-height ratio WtHR is another tool to assess body size.

According to research , higher WtHR has associations with worse cholesterol and blood pressure, even at a healthy BMI.

For this reason, WtHR may be helpful when assessing health risk when used along with other measures of health. To calculate WtHR, divide waist size by height. If the result is 0. A study concluded that a WtHR of 0.

However, this study did not account for ethnicity. For example, a 30 year old male with a 0. On average, a female of the same age and WHtR may be at risk of a 4. While population-level studies are important, individual health is about more than waist size alone.

A person should talk with their doctor if they have concerns about the health risks that may have links to a higher WtHR. Learn how to measure the waist.

This includes fat found in many different parts of the body. Body fat is necessary for the human body to function. An individual needs a type called essential fat to survive — it is critical for the development of the brain, bone marrow, nerves, and membranes.

Other types of fat protect the internal organs in the chest and abdomen, and the body can use it if necessary for energy.

According to the American Council for Exercise , these are the expected body fat ranges for adults:. Typically, obesity has associations with a high proportion of body fat.

Obesity and overweight can carry a greater risk for conditions such as:. Calculating body fat percentage can provide useful information because it reflects body composition, unlike BMI, WHR, and WtHR.

Learn more about body fat levels by age and sex. The most common way of measuring body fat percentage is to use a skinfold measurement, which uses special calipers to pinch the skin.

A health professional will measure tissue on the thigh, abdomen, and chest for males or upper arm for females. While none of these can give a completely accurate reading, the estimates can be close enough to offer a reasonable assessment. Learn more about the different ways to measure body fat.

One method a person can use to determine their ideal weight is body mass index BMI measurements. According to the National Heart, Lung, and Blood Institute , a good weight for a person who is 5 foot ft 4 inches in tall ranges from — pounds lbs.