Obesity

Obesity is a condition of excessive fatness. Fatness is often expressed as a percentage of body weight. Prepubertal boys and girls typically have about 15 percent of their body weight as fat, while the average adult male is 20 percent fat, and the average adult female is 30 percent fat. Body fatness is measured using a variety of techniques, such as body densitometry, electrical impedance, and skin-fold thickness. Total body weight, although it includes muscle, bone, and internal organs, in addition to body fat, can be used as an index of fatness, especially when expressed in relation to body height. A ratio of weight and height, called the body mass index (BMI), has been adopted for use in the assessment of children, adolescents, and adults. BMI is calculated by dividing the weight, in kilograms, by the square of the height, in meters (kg/m2). If pounds and inches are used, then the quotient (pounds divided by inches squared) multiplied by 704.5. For adult men and women, BMI greater than 25 signifies overweight, and BMI greater than 30 indicates obesity. During childhood, BMI varies by gender and normally increases with age. Obesity is determined with a graph or reference table that gives the eighty-fifth percentile for age (as a criteria for overweight) and the ninety-fifth percentile for age (as a criteria for obese) for boys and girls. In 2000 the CDC published revised percentile standards for BMI (see Table).