Occupational Health Physician

Abstract

Synonyms Severe overweight; Adiposity Definition Obesity is defined as disease in which excess body fat has accumulated to such an extent that health is adversely affected. Body Mass Index (BMI, i. e. weight in kg / (height in m) 2) is the population measure of obesity BMI does not account for body composition and variations in fat distribution. Cut offs are defined according to BMI-associated morbidity. Ethnic populations differ in the level of risk associated with a particular BMI. In Caucasian adults BMI is normal between 18.5 and 24.9 kg/m 2. Values between 25.0 and 29.9 kg/m 2 correspond to overweight (over-weight or preobese), >30.0 kg/m 2 denotes obesity. Obesity can be further classified into class I (moderate, 30.0-34.9 kg/m 2), class II (severe, 35.0-39.9 kg/m 2) and class III (very severe, >40.0 kg/m 2). In children and adolescents national and international BMI reference percentiles are used with the 90th and 97thP as cut offs for overweight and obesity, respectively. In the US 85th and 95thPs are used. The association between BMI and body fat varies according to body build and proportion as well as across populations. Alternatively direct measures of body fat (e. g. anthropometric or bioelec-trical impedance measurements) are used in population surveys with values >25 (males) and >30% of body weight (females) denoting overfat. Abdominal (or vis-ceral) fat carries the highest metabolic risk. Waist circumference (measured at the midpoint between lower border of the rip cage and the iliac crest) is a population measure of abdominal fat. Risk is increased above 94 (males) and 80 cm (females). Risk is substantially increased at >102 and >88 cm, respectively. The waist associated risk is independent and additive to the BMI-associated risk. The waist to hip ratio (w/h) is related to cardiovascular risk. w/h is the ratio between risk (i. e. w = excess abdominal fat) and protective factors (i. e. hip circumference is related to fat free mass). w/h-cut offs are >1.0 in males and >0.85 in females. Taken together weight, fat and waist characterize obesity and its health risks. Basic Characteristics Levels and Trends There is a world wide increase in the prevalence of overweight and obesity. In adult populations prevalence of overweight plus obesity varies between about 30% (China) and more than 60% (industrialized countries). Corresponding prevalences of obesity range between 3 and above 25%. Prevalence of overweight children and adolescents is between 5 to 20% with considerable differences between countries, e. g. there is a north-south gradient in Europe with highest values in southern European countries. Trend data suggest steep rises in prevalences of overweight and obesity during the past 25 years, e. g. there is a 2-to 5-fold increase in overweight prevalence in children and adolescents in Germany. In non developed countries increases in overweight and obesity are strongly associated with transition and economic growth. A further increase in over