Body weight is the most widely used anthropometric indicator of nutritional reserves, and weight relative to height is an acceptable measure of body size for growth monitoring and for most epidemiological surveys. Overweight and obesity, though often used synonymously, are not the same. S. Abraham and co-workers (1983) clearly made the distinction in analyzing data from the first U. S. National Health and Nutrition Examination (NHANES) survey. Overweight was defined as an excess in body weight relative to a range of weights for height. In this report, individuals over the 85th percentile of weight for height standards are considered overweight. Obesity was defined as an excess of body fat based on the sum of the triceps (upper arm) skinfold and subscapular (back) skinfold. Skinfold measurements using calipers that pinch a fold of skin and subcutaneous fat at specific sites (for example, waist, abdomen, thighs, upper arm, and back) are used in equations to estimate body fat stores and are compared with reference percentile tables (Himes 1991).
Many recent studies have used the Body Mass Index (BMI), which is the weight in kilograms divided by height in meters squared, to categorize body size. This index was devised by the Belgian mathematician Adolphe Quetelet (1796-1874) and is also referred to as the Quetelet index. (The Ponderal Index, which is the quotient of the height in inches divided by the cube root of the weight in pounds, has been similarly used.)
Overweight is defined as a BMI above 27.3 for women and 27.8 for men. These BMIs represent approximately 124 percent of desirable weight for men and 120 percent of desirable weight for women, defined as the midpoint of the range of weight for a medium-size skeletal frame from the 1983 Metropolitan Insurance Company Height and Weight Tables. The World Health Organization uses a similar range of BMIs: below 20 (lean), 20 to 25 (acceptable), 25 to 29 9 (moderately overweight), 30 to 39 9 (severely obese), and greater than 40 (morbidly obese). Epidemiological studies frequently use a BMI of 30 as the delimiter for obesity for both sexes.
Other anthropometric measurements have been used as alternatives to body weight in assessment of obesity. Body girth measurements or circumferences at specific anatomical locations have a high correlation with body mass. A commonly used measure is the circumference of the upper arm. This measurement, in conjunction with the triceps skinfold, has been used to compare the fat and lean components of the arm and thus to provide a measurement of energy and protein stores. More sophisticated, expensive, and time-consuming techniques assess the lean and fat components of the body. These techniques have included densitometry, magnetic resonance imaging (MRI), basic X rays, computerized tomography (CAT) scans, ultrasound, bioelectrical impedance, total body water, and body potassium levels (Lukaski 1987).
Skinfolds, circumferences, and imaging techniques assess the regional distribution of fat deposits. A central distribution of fat is referred to as an apple shape. A lower torso distribution of fat on the hips is referred to as a pear shape. The apple shape, often measured as a high waist-to-hip ratio of circumferences, is associated with internal deposits of abdominal fat and increased risk for coronary artery disease and adult onset diabetes. By contrast, the pear shape is not associated with increased disease risk (Bouchard and Johnston 1988).
World History
