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What is childhood obesity? How do health-care professionals diagnose
In order to systematically describe obesity, the concept of body mass index (BMI) was developed. BMI is the ratio between an individual's weight to height relative to their gender and age. BMI addresses the following question: Is the weight of the subject in excess of what is healthy for a given height? Generally (but not always), BMI correlates with the amount of body fat, but it is not a measurement of fat. An individual who has more than the average muscle mass for a given height (for example, weightlifters) will have an elevated BMI but clearly will not be obese. Nomograms for both adults and children have been developed to graphically represent the range of normal when measuring BMI. An individual is overweight when their BMI is between 25.0-29.9. Obesity is defined as a BMI greater than 30.0. Many web sites have calculators to measure BMI (for example, http://www.cdc.gov/healthyweight/assessing/bmi/). Measuring body fat may be done via skin-fold-thickness measurement, waist-to-hip-circumference ratio, and neutral buoyancy (water displacement) measurements. BMI is not used for children under 2 years of age, and instead growth charts should be used to identify any weight issues.