At what age can the body mass index BMI be used to accurately assess a childs height and weight proportion?
Determining Body Mass Index for TeensWhat is body mass index?Determining how much your teen should weigh is not a simple matter of looking at an insurance height-weight chart. It includes considering the amount of bone, muscle, and fat in his or her body. The amount of fat is the critical measurement. Show
A good indicator of how much fat your teen carries is the body mass index (BMI). Although it's not a perfect measure, it gives a fairly accurate assessment of how much of your teen's body is composed of fat. The formulas below apply to adults only. For children and teens ages 2 to 19 years, the BMI varies by age and sex. An additional step must be done after the BMI has been determined using one of the formulas below. The BMI-for-age percentile is determined by comparing your teen's weight to that of other teens of the same age and sex. In other words, by plotting your child's BMI value into the CDC's BMI-for-age growth chart , you can determine if your child is underweight, within normal range, overweight, or obese. Or you can easily calculate it from the CDC's online tool . To calculate an adult's BMI using the English formulaFor example, a person who weighs 165 pounds and is 5 feet 4 inches tall has a BMI of 28. 165 lbs x 703=28(64 inches) x (64 inches) To calculate an adult's BMI using the metric formulaA BMI between 25 to 29.9 is considered overweight. Anything over 30 is considered obese. Normal BMI is between 18.5 and 24.9. BMI cut-offs for people of South Asian descent are different. BMI can be calculated using pounds and inches. BMI= Weight in Pounds x 703 (Height in Inches) x (Height in Inches) Multiply your weight in pounds by 703. Divide that answer by your height in inches. Divide that answer by your height in inches again. BMI can be calculated using kilograms and meters. BMI= Weight in Kilograms (Height in Meters) x (Height in Meters) Your weight in kilograms. Divided by your height in meters. Divide that answer by your height in meters again. For example, a person who weighs 99.79 Kilograms and is 1.905 Meters tall has a BMI of 27.5. 99.79 Kg=27.5(1.905 Meters) x (1.905 Meters) What is body mass index (BMI)?Body mass index (BMI) is a medical screening tool that measures the ratio of your height to your weight to estimate the amount of body fat you have. Healthcare providers calculate BMI by using weight in kilograms (kg) divided by the square of height in meters (m2). In most people, BMI correlates to body fat — the higher the number, the more body fat you may have — but it’s not accurate in some cases. BMI alone does not diagnose health. Healthcare providers use BMI and other tools and tests to assess someone’s health status and risks. High body fat may lead to heart disease, stroke and Type 2 diabetes. Low body fat may be related to malnutrition. Just the right amount of body fat helps vitamins and minerals get into your body. It also provides a source of energy for your body, helps maintain body temperature and protects your organs. You should not use the standard BMI chart to evaluate a child’s or teenager’s weight. Talk to your child's healthcare provider about the optimum weight range for their age and height. What is BMI used for?Healthcare providers use BMI to help diagnose weight types and as a screening tool for certain health conditions. Diagnosing weight types with BMIIn general, the following BMI ranges (in kg/m2) classify different weight types:
BMI isn’t the only tool providers use to classify weight types. Other tools include:
Screening for health risks with BMIIf you have a BMI less than 18.5 (underweight), you may be at higher risk for developing the following conditions:
If you have underweight, your healthcare provider will likely order certain blood tests and other tests to check your overall health and to see if you’re malnourished. In general, the higher your BMI, the higher your risk for the following conditions:
It’s important to remember that you could have any of the above health conditions without having a high BMI. Similarly, you could have a high BMI without having any of these conditions. Genetics and other factors, such as smoking cigarettes, play a large role in the development of these conditions. If your BMI reveals you may have obesity, your provider will likely order certain blood tests to check your general health, such as a comprehensive metabolic panel and lipid panel. How do I calculate my BMI?You can calculate BMI yourself with these steps:
For example, a person who weighs 180 lbs. and is 5 feet and 5 inches tall (65 inches total) would calculate their BMI in the following way:
Their BMI would be 29.9. What is a healthy BMI?The optimum range for a healthy BMI is considered to be 18.5 to 24.9. It’s important to remember that body fatness isn’t the only determiner of overall health. Several other factors, such as genetics, activity level, smoking cigarettes or using tobacco, drinking alcohol and mental health conditions all affect your overall health and your likelihood of developing certain medical conditions. What are the limitations of BMI?The standard BMI chart has limitations for various reasons. Because of this, it’s important to not put too much emphasis on your BMI. Even though the BMI chart can be inaccurate for certain people, healthcare providers still use it because it’s the quickest tool for assessing a person’s estimated body fat amount. Limitations of using BMI to help diagnose weight typesThe standard BMI has limitations in regards to diagnosing weight types, including:
You shouldn’t use the standard BMI chart to assess the amount of body fat of the following populations:
Limitations of using BMI as a screening tool for health conditionsThe BMI as a screening tool for assessing the risk of certain health conditions, such as Type 2 diabetes and heart disease, has some limitations, including:
A note from Cleveland Clinic Body mass index (BMI) is a quick tool that healthcare providers can use to assess your risk for certain health conditions. However, BMI is not always an accurate measurement of body fatness and is not the sole determiner of your general health. If you have any questions or concerns about your weight or your risk for developing certain health conditions, such as heart disease, talk to your healthcare provider. They’re available to help. At what age do you measure BMI?BMI-for-age is the measure that can be used continuously from age 2 to 20 years to screen for obesity, overweight, or underweight. BMI-for-age is not recommended for use in the United States before 2 years of age to screen for overweight, obesity, or underweight.
Is BMI same for all ages?For this reason, BMI calculations are different for children and teens. These measurements take age and sex into account. Norm can also vary among people of certain races and ethnicities.
What is BMI used to measure in children?Body mass index (BMI) is commonly used to determine childhood weight status. BMI is calculated by dividing a person's weight in kilograms by the square of height in meters. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.
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